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gated.conf(4)
NAME
gated.conf - Gate daemon configuration file (general information)
DESCRIPTION
The gated.conf file contains configuration information that is read by the
gated daemon at initialization time. This file contains statements that
control tracing options, select routing protocols, manage routing
information, and manage independent system routing.
The /etc/gated.conf file is defined as a Context-Dependent Symbolic Link
(CDSL), and must be maintained as such. See the System Administration
manual for more information.
The gated.conf file consists of a sequence of statements terminated by a
semi-colon (;). Statements are composed of tokens separated by any
combination of blanks, tabs, and newlines. This structure simplifies
identification of the parts of the configuration associated with each other
and with specific protocols. Comments can be specified by either of the
following:
· A number sign (#)
· The C-style /* and */ characters.
Syntax description conventions
Keywords and special characters that the parser expects are displayed using
the HTML strong style. Parameters are specified in the HTML variable
definition style. Parameters shown in brackets ([]) show optional keywords
and parameters. The vertical bar (|) indicates a choice of optional
parameters. Parentheses (()) group keywords and parameters, when
necessary. For example:
backbone | (area area)
In this example, the brackets indicate that either parameter is optional.
The keywords are backbone and area. The vertical bar indicates that either
backbone or area area can be specified. Because area is in the variable
definition0 style, it is a parameter that needs to be provided.
Statement Grouping
The configuration statements and the order in which they must appear in the
gated.conf file are as follows:
· options statements
· interface statements
· definition statements
· protocol statements
· static statements
· control statements
· aggregate statements
Entering a statement out of order causes an error when parsing the
configuration file.
Two other types of statements do not fit in these categories: %directive
statements and %trace statements. These statements provide instructions to
the parser and control tracing from the configuration file. They do not
relate to the configuration of any protocol and may occur anywhere in the
gated.conf file.
Configuration Statement Summary
The following table lists each gated.conf configuration statement by name,
identifies the statement type, and gives a synopsis of the statement's
function:
__________________________________________________________________
Name Type Synopsis
__________________________________________________________________
%directory directive
Sets the directory for include
files.
%include directive
Includes a file into gated.conf.
traceoptions trace Specifies which events are traced.
options definition Defines gated options.
interfaces definition
Defines gated interfaces.
autonomoussystem definition Defines the AS number.
routerid definition
Defines the originating router
(BGP, OSPF).
martians definition
Defines invalid destination
addresses.
rip protocol Enables the RIP protocol.
isis protocol Enables the ISIS protocol.
kernel protocol
Configures kernel interface
options.
ospf protocol Enables the OSPF protocol.
egp protocol Enables the EGP protocol.
bgp protocol Enables the BGP protocol.
redirect protocol
Configures the processing of ICMP
redirects.
icmp protocol
Configures the processing of
general ICMP packets.
snmp protocol Enables reporting to SNMP.
pim protocol Enables PIM protocol.
dvrmp protocol Enables DVRMP protocol.
msdp protocol Enables MSDP protocol.
static static Defines static routes.
import control Defines which routes to import.
export control Defines which routes to export.
aggregate control Defines which routes to aggregate.
generate control Defines which routes to generate.
__________________________________________________________________
ROUTING AND PREFERENCES
The gated.conf files can define routes from one protocol or peer to
another, assigning each route a value called a preference.
The preference value determines the order of routes to the same destination
in a single routing database. The active route is chosen by the lowest
preference value.
Some protocols implement a second preference (preference2), sometimes
referred to as a tie breaker.
Use the following guidelines when setting preferences:
· It can be set in several different configuration statements in
gated.conf, although the last or most specific value set for a route
is the one used. (See gated_intro(7).)
· It can be specify one network interface over another, one protocol
over another, or one remote gateway over another.
· It cannot be used to control the selection of routes within an
interior gateway protocol (IGP). That function is accomplished
automatically by the protocol based on metric.
· It can be used to select routes from the same exterior gateway
protocol (EGP) learned from different peers or autonomous systems.
Selecting a Route
The gated daemon uses the following criteria to select a route:
· The route with the best (numerically smallest) preference, as defined
in the gated.conf file, is preferred.
· If the two routes have the same preference, the route with the best
(numerically smallest) preference2 (also known as a tie breaker) is
preferred.
· If autonomous system (AS) path information is available it is used to
help determine the most preferred route as follows:
-- A route with an AS path is preferred over one without and AS
path.
-- If the AS paths and origins are identical, the route with the
lower metric is preferred.
-- A route with an AS path origin of IGP is preferred over a route
with an AS path origin of EGP. The least preferred is an AS path
with an unknown origin.
-- A route with a shorter AS path is preferred.
· A route with the lowest Multi-Exit Discriminator (MED)is preferred.
MEDs are only compared between routes that were received from the same
neighbor AS. (This test is only applied if the local AS has two or
more connections to a given neighbor AS.)
· A route learned from an IGP is preferred to a route learned from an
EGP. The least preferred is a route learned indirectly by an IGP from
an EGP.
· The route with the lowest numeric next-hop address is used.
· If both routes are from the same protocol and AS, the one with the
lowest metric is preferred.
Assigning Preferences
A default preference is assigned to each source from which gated receives
routes. Preference values range from 0 to 255, with the lowest number
indicating the most preferred route.
The following table lists each type of route, the statement (or clause
within statements) that sets preference for the route, and the default
preference for each type of route.
Note that a statement that is narrow in scope has a higher precedence given
to its preference value, but affects a smaller set of routes.
___________________________________________________________________
Preference of Defined by Statement Default
___________________________________________________________________
Direct connected networks interface 0
OSPF routes ospf 10
IS-IS level 1 routes isis level 1 15
IS-IS level 2 routes isis level 2 18
Internally generated default gendefault 20
Redirects redirect 30
Routes learned via route socket kernel 40
Static routes from config static 60
ANS SPF (SLSP) routes slsp 70
RIP routes rip 100
Point-to-point interface 110
Routes to interfaces that are down interfaces 120
Aggregate/generate routes aggregate/generate 130
OSPF AS external routes ospf 150
BGP routes bgp 170
EGP egp 200
___________________________________________________________________
Multi-Exit Discriminator
The Multi Exit Discriminator, or MED, allows the administrator of a routing
domain to choose between various exits from a neighboring AS. The gated
daemon uses this attribute to choose the best route to the neighboring AS.
If all the other factors for a path to a given AS are equal, the path with
the lower MED value takes preference over other paths.
This attribute is not propagated to other neighboring ASs. This attribute
can be propagated, however, to other BGP speakers within the same AS.
The MED attribute, for BGP version 4, is a four-octet unsigned integer.
You originate a MED by using the metricout option of group or peer
statements or the metric option of the export statement. You import a MED
by using the med keyword on the BGP group statement.
You must specify the med keyword on the group statement for gated to
consider metrics when calculating a next hop (the default action is to
ignore MEDs).
The following example shows the metricout option when specified on the
group statement:
group type external peeras 31337 metricout 5 {
peer 192.168.10.32;
peer 192.168.10.33;
};
The following example shows the metricout option when specified on the peer
statement:
group type external peeras 31337 {
peer 192.168.10.32 metricout 2;
peer 192.168.10.33 metricout 3;
};
The following example shows the metric keyword when specified on the export
statement:
export proto bgp as 31337 metric 5 {
proto static {
all;
};
};
The following example shows another case of specifying the metric keyword
on the export statement:
export proto bgp as 31337 {
proto bgp as 64000 metric 1 {
all;
};
proto static metric 3 {
all;
};
proto direct metric 7 {
all;
};
};
Sample Preference Specifications
In the following statements, the preference applicable to routes learned
via RIP from gateway 138.66.12.1 is 75. The last preference applicable to
routes learned via RIP from gateway 138.66.12.1 is defined in the accept
statement. The preference applicable to other RIP routes is found in the
rip statement. The preference set on the interface statement applies only
to the route to that interface.
interfaces {
interface 138.66.12.2 preference 10 ;
} ;
rip yes {
preference 90 ;
} ;
import proto rip gateway 138.66.12.1 preference 75 ;
TRACE OPTIONS STATEMENT
Trace options statements control tracing options. The gated daemon's
tracing options may be configured at many levels. Tracing options include
the file specifications, control options, and global and protocol-specific
tracing options. Unless overridden, tracing options from the next higher
level are inherited by lower levels. For example, Border Gateway Protocol
(BGP) peer tracing options are inherited from BGP group tracing options,
which are inherited from global BGP tracing options, which are inherited
from global gated tracing options. At each level, tracing specifications
override the inherited options.
Syntax
traceoptions [trace_file [replace] [size size[k|m] files files]]
[control_options] trace_options [except trace_options];
traceoptions none ;
trace_file
Specifies the file to receive tracing information. If this file name
does not begin with a slash (/), the directory in which gated was
started is prepended to the name.
replace
Replaces an existing trace file. The default is to append to an
existing file.
size size[k|m] files files
Limits the maximum size of the trace file to the specified size
(minimum 10 kilobytes). When the trace file reaches the specified
size, it is renamed to file.0, then file.1, file.2, up to the maximum
number of files (minimum specification is 2).
control_options
Specifies options that control the appearance of tracing. The only
valid value is nostamp, which specifies that a time stamp should not be
prepended to all trace lines.
trace_options
See the Global Tracing Options section for more information.
except trace_options
Enables a broad class of tracing and then disables more specific
options. See the Global Tracing Options section for more information.
none
Specifies that all tracing should be turned off for this protocol or
peer.
Global Tracing Options
There are two types of global options: those with global significance and
those with protocol significance.
Global Significance
The following trace flags have global significance:
parse
Traces the lexical analyzer and parser. Used mainly by gated
developers for debugging.
adv Traces the allocation of and freeing of policy blocks. Used mainly by
the gated developers for debugging.
symbols
Traces symbols read from the kernel at startup. The principal means to
specify this level of tracing is by the -t option on the command line,
because the symbols are read from the kernel before parsing the
configuration file.
iflist
Traces the reading of the kernel interface list. Specify this with the
-t option on the command line because the first interface scan is done
before reading the configuration file.
Protocol Significance
The following options flags have potential significance to protocols:
all Turns on all of the options flags.
general
A shorthand notation for specifying both normal and route.
normal
Traces normal protocols occurrences. Abnormal protocol occurrences are
always traced.
route
Traces routing table changes for routes installed by this protocol or
peer.
state
Traces state machine transitions in the protocols.
policy
Traces application of protocol and user-specified policy to routes
being imported and exported.
task
Traces system interface and processing associated with this protocol or
peer.
timer
Traces timer usage by this protocol or peer.
Note
Not all of these options apply to all of the protocols. In some
cases, their use does not make sense (for instance, RIP does not have
a state machine) and in some instances the requested tracing has not
been implemented (such as RIP support of the policy option).
It is not possible to specify packet tracing from the command line
because a global option for packet tracing would potentially create
too much output.
When protocols inherit their tracing options from the global tracing
options, tracing levels that do not make sense (such as parse, adv, and
packet tracing options) are masked out.
Global tracing statements have an immediate effect, especially parsing
options that affect the parsing of the configuration file. Tracing values
inherited by protocols specified in the configuration file are initially
inherited from the global options in effect as they are parsed, unless they
are overridden by more specific options.
After the configuration file is read, tracing options that were not
explicitly specified are inherited from the global options in effect at the
end of the configuration file.
Packet tracing
The tracing of packets is flexible. Every protocol has one or more options
for tracing packets. All protocols allow the packets keyword to be used
for tracing all packets sent and received by the protocol. Most protocols
have other options for limiting tracing to a useful subset of packet types.
These tracing options can be further controlled with the following
modifiers:
detail
Specifies a more verbose format to provide more information about the
contents of the packet. The detail option must be specified before
send or recv. By default, packets are traced in a terse form of one or
two lines.
send
Limit the tracing to packets sent. If neither send nor recv option is
specified, both sent and received packets are traced.
recv
Limit the tracing to packets received. If neither send nor recv option
is specified, both sent and received packets are traced.
Note
If a protocol allows for several different types of packet tracing,
modifiers can be applied to each individual type. Be aware, however,
that within one tracing specification the trace flags are summed up,
so specifying detail packets turns on full tracing for all packets.
DIRECTIVE STATEMENTS
Directive statements provide direction to the gated configuration language
parser about included files and the directories in which these files
reside. Directive statements are immediately acted upon by the parser.
Other statements terminate with a semi-colon (;), but directive statements
terminate with a newline. The two directive statements are as follows:
%directory directory
Defines the directory in which the include files are stored. When it
is used, gated searches the directory identified by pathname for any
included files that do not have a fully qualified file name (do not
begin with "/"). This statement does not change the current directory;
it only specifies the prefix applied to included file names.
%include filename
Identifies an include file. The contents of the file are included in
the gated.conf file at the point where the %include directive is
located. If the file name is not fully qualified (does not begin with
"/"), it is considered to be relative to the directory defined in the
%directory directive. The %include directive statement causes the
specified file to be parsed completely before resuming with this file.
Nesting up to ten levels is supported. The maximum nesting level can
be increased by changing the definition of FI_MAX in the parse.h file.
In a complex environment, segmenting a large configuration into smaller
more easily understood segments might be helpful, but one of the advantages
of gated is that it combines the configuration of several different routing
protocols into a single file. Segmenting a small file unnecessarily
complicates routing configurations.
OPTIONS STATEMENTS
The options statement allows specification of some global options. If
used, the options statement must appear before any other type of
configuration statement in the gated.conf file.
Syntax
options
[nosend]
[noresolv]
[gendefault [preference preference] [gateway gateway]]
[syslog [upto] log_level]
[mark time]
;
The options list can contain one or more of the following options:
gendefault [preference preference] [gateway gateway]
When gendefault is enabled and a BGP or EGP neighbor is up, a default
route with the special protocol default is created. This can be
disabled per BGP/EGP group with the nogendefault option. By default,
this route has a preference of 20. This route is normally not
installed in the kernel forwarding table; it is only present so it can
be announced to other protocols.
If a gateway is specified, the default route is installed in the kernel
forwarding table with a next hop of the listed gateway.
Note that the use of the more general generate default option is
preferred to the use of the gendefault option. The gendefault option
may be removed in the future. See the section on "Route Aggregation"
in gated.control(4) for more information on the generate statement.
nosend
Do not send any packets. This option makes it possible to run gated on
a live network to test protocol interactions without actually
participating in the routing protocols. The packet traces in the gated
log can be examined to verify that gated is functioning properly. This
is useful for RIP and possibly the SMUX SNMP interface. This option
does not apply to BGP and is not useful with EGP and OSPF.
noresolv
By default, gated tries to resolve symbolic names into IP addresses by
using the gethostbyname() and getnetbyname() library calls. These calls
usually use the Domain Name System (DNS) instead of the host's local
host and network tables. If there is insufficient routing information
to send DNS queries, gated deadlocks during startup. This option can
be used to prevent these calls; symbolic names result in configuration
file errors.
syslog [upto] log_level
Controls the amount of data gated logs via syslog on systems where
setlogmask() is supported. The available logging levels and other
terminology are as defined in setlogmask(3). The default is equivalent
to syslog upto info.
mark time
Specifying this option causes gated to output a message to the trace
log at the specified interval. This can be used to determine if gated
is still running.
INTERFACES STATEMENT
An interface is the connection between a router and one of its attached
networks. A physical interface can be specified by interface name, by IP
address, or by domain name (unless the network is an unnumbered point-to-
point network). Multiple levels of reference in the configuration language
allow identification of interfaces using a wild card or interface type
name. Be careful with the use of interface names because future versions
might allow more than one address per interface. The interface_list is a
list of one or more interface names including wildcard names (names without
a number) and names that may specify more than one interface or address, or
the token all for all interfaces.
Syntax
interfaces {
options
[strictinterfaces]
[scaninterval time]
[aliases-nexthop ( primary | lowestip | keepall
)]
;
interface interface_list
[preference preference]
[down preference preference]
[passive]
[simplex]
[reject]
[blackhole]
[AS autonomoussystem]
;
define address
[broadcast address | pointtopoint address]
[netmask mask]
[multicast]
;
} ;
options
Allows configuration of the following global options related to
interfaces:
strictinterfaces
Indicates that it is a fatal error to reference an interface in the
configuration file that is not present when gated is started and
not listed in a define statement. Without this option, a warning
message is issued but gated continues.
scaninterval time
Specifies how often gated scans the kernel interface list for
changes. The default is every 15 seconds on most systems, and 60
seconds on systems that pass interface status changes through the
routing socket (for example, BSD 4.4). Note that gated also scans
the interface list on receipt of a SIGUSR2.
aliases-nexthop (primary | lowestip | keepall)
Specifies which address gated will install as the next hop for
interface routes. If primary is used, the primary interface
address (default) will be installed. If lowestip is used, the
address with the lowest IP address will be installed. If keepall
is used, all interface routes are kept in the kernel up to a
maximum of RT_N_MULTIPATH routes. The aliases-nexthop option is a
global parameter that can be overridden for interfaces using the
interface option.
interface interface_list
Sets interface options on the specified interfaces. An interface list
is all or a list of interface names (see the "Interface Lists"
section), domain names, or numeric addresses. Options available on
this statement are:
preference preference
Sets the preference for routes to this interface when it is up and
appears to be functioning properly. The default preference is 0.
down preference preference
Sets the preference for routes to this interface when gated does
not believe it to be functioning properly, but the kernel does not
indicate it is down. The default value is 120.
passive
Prevents gated from changing the preference of the route to this
interface if it is not believed to be functioning properly due to
lack of received routing information. The gated daemon only
performs this check if the interface is actively participating in a
routing protocol.
simplex
Defines an interface as unable to hear its own broadcast packets.
Some systems define an interface as simplex with the IFF_SIMPLEX
flag; others require it to be specified in the configuration file.
On simplex interfaces, a sender's own packets are assumed to have
been looped back in software and are not used as an indication that
the interface is functioning properly.
reject
Specifies that the address of the interface matching these criteria
is used as the local address when installing reject routes in the
kernel. Use this only with systems based on BSD 4.3 Tahoe or
earlier that have installed a reject/blackhole pseudointerface.
blackhole
Specifies that the address of the interface matching these criteria
is used as the local address when installing reject routes in the
kernel. Use this only with systems based on BSD 4.3 Tahoe or
earlier that have installed a reject/blackhole pseudo interface.
AS autonomoussystem
Specifies the AS that will be used to create an AS path associated
with the route created from the definition of this interface.
define address
Defines interfaces that might not be present when gated is started so
they may be referenced in the configuration file when strictinterfaces
is defined. The following are valid define keywords:
broadcast address
Defines the interface as broadcast capable (for example, Ethernet
or Token Ring) and specifies the broadcast address.
pointopoint address
Defines the interface as a point-to-point interface (for example,
SLIP or PPP) and specifies the address on the local side. The
first address on the define statement references the address of the
host on the remote end of the interface, the address specified
after this pointopoint keyword defines the address on the local
side of the interface.
An interface that is not defined as broadcast or point-to-point is
assumed to be nonbroadcast multiaccess (NBMA), such as an X.25
network.
netmask mask
Specifies the subnet mask to be used on this interface. This is
ignored on point-to-point interfaces.
multicast
Specifies that the interface is multicast capable.
Interface Lists
An interface list is a list of references to interfaces or groups of
interfaces. The following four methods, from most general to most
specific, are available for referring to interfaces:
all Refers to all available interfaces.
Interface name wildcard
Refers to all the interfaces of the same type. Tru64 UNIX interfaces
consist of the device driver name and a unit number; for example, le0.
References to the name contain only alphabetic characters and match any
interfaces that have the same alphabetic part.
For example, le refers to all Lance Ethernet interfaces, but le does
not match lel0.
Interface name
Refers to a specific interface, usually one physical interface. These
are specified as an alphabetic part followed by a numeric part. This
will match one specific interface. But be aware that on many systems,
there can be more than one protocol (for example, IP) address on a
given physical interface. For example, ee1 matches an interface named
ee1, but not an interface named ee10.
Interface address
Matches one specific interface. The reference can be by protocol
address (for example, 10.0.0.51) or by symbolic host name (for example,
nic.ddn.mil). Note that a symbolic host name reference is only valid
when it resolves to only one address. Use of symbolic host names is
not recommended.
If many interface lists are present in the gated.conf file with more than
one parameter, these parameters are collected at run time to create the
specific parameter list for a given interface. If the same parameter is
specified on more than one list, the parameters with the most specific
interface are used.
For example, the following interface list is for a system with three
interfaces, le0, le1, and du0:
rip yes {
interface all noripin noripout ;
interface le ripin ;
interface le1 ripout ;
} ;
In this example, RIP packets are accepted from interfaces le0 and le1, but
not from du0. RIP packets are sent only on interface le1.
IP Interface Addresses and Routes
The BSD 4.3 and later networking implementations allow the following four
types of interfaces. Some implementations allow multiple protocol
addresses per physical interface, but these are mostly based on BSD 4.3
Reno or later.
loopback
This interface must have the address of 127.0.0.1. Packets sent to
this interface are sent back to the originator. This interface is also
used as an interface for implementing other features, such as reject
and blackhole routes. Although a netmask is reported on this
interface, it is ignored. It is useful to assign an additional address
to this interface that is the same as the OSPF or BGP router ID; this
allows routing to a system based on the router ID that will work if
some interfaces are down.
broadcast
This is a multiaccess interface capable of a physical level broadcast,
such as Ethernet, Token Ring, and FDDI. This interface has an
associated subnet mask and broadcast address. The interface route to a
broadcast network is a route to the complete subnet.
point-to-point
This is a tunnel to another host, usually on some sort of serial link.
This interface has a local address and a remote address. Although it
may be possible to specify multiple addresses for a point-to-point
interface, there is no useful reason for doing so.
The remote address must be unique among all the interface addresses on
a given router. The local address may be shared among many point-to-
point interfaces and up to one non-point-to-point interface. This is
technically a form of the router ID method for addressless links. This
technique conserves subnets, because none are required when using this
technique.
If a subnet mask is specified on a point-to-point interface, it is only
used by RIP version 1 to determine which subnets may be propagated to
the router on the other side of this interface.
non-broadcast multi-access or nbma
This type of interface is multiaccess, but not capable of broadcast;
for example frame relay and X.25. This type of interface has a local
address and a subnet mask.
The gated daemon ensures that there is a route available to each IP
interface that is configured and up. Typically this this done by the
ifconfig command that configures the interface; gated does it to ensure
consistency.
For point-to-point interfaces, gated installs some special routes. If the
local address on one or more point-to-point interfaces is not shared with a
non-point-to-point interface, gated installs a route to the local address
pointing at the loopback interface with a preference of 110. This ensures
that packets originating on this host destined for this local address are
handled locally.
OSPF prefers to route packets for the local interface across the point-to-
point link where they will be returned by the router on the remote end.
This is used to verify operation of the link. Because OSPF installs routes
with a preference of 10, these routes override the route installed with a
preference of 110.
If the local address of one or more point-to-point interfaces is shared
with a non-point-to-point interface, gated installs a route to the local
with a preference of 0 that is not installed in the forwarding table. This
prevents protocols like OSPF from routing packets to this address across a
serial interface when this system could be functioning as a host.
When the status of an interface changes, gated notifies all the protocols,
which take the appropriate action. The gated daemon assumes that interfaces
that are not marked UP do not exist.
The gated daemon ignores any interfaces that have invalid data for the
local, remote, or broadcast addresses or the subnet mask. Invalid data
includes zeros in any field. The gated daemon also ignores any point-to-
point interface that has the same local and remote addresses; it assumes it
is in some sort of loopback test mode.
DEFINITION STATEMENTS
Definition statements are general configuration statements that relate to
all of gated, or at least to more than one protocol. The three definition
statements are autonomoussystem, routerid, and martians. If used,
autonomoussystem, routerid, and martians must appear before any other type
of configuration statement in gated.conf file.
Autonomous System Syntax
autonomoussystem autonomous_systemloops number ;
Sets the autonomous system number of this router to be autonomous_system.
This option is required if BGP or EGP are in use. The AS number is assigned
by the Network Information Center (NIC).
The loops parameter is only for protocols supporting AS paths, such as BGP.
It controls the number of times this autonomous system may appear in an AS
path and defaults to 1 (one).
Router ID Syntax
routerid host ;
Sets the router identifier for use by the BGP and OSPF protocols. The
default is the address of the first interface encountered by gated. The
address of a non-point-to-point interface is preferred over the local
address of a point-to-point interface and an address on a loopback
interface that is not the loopback address (127.0.0.1) is most preferred.
Martian Syntax
Sometimes a misconfigured system sends out invalid destination addresses.
These invalid addresses, called martians, are rejected by the routing
software. A martian configuration defines a list of martian addresses from
which all routing information is ignored. A martian configuration is
structured as follows:
martians {
host host [allow] ;
network [allow] ;
network mask mask [allow] ;
network masklen number [allow] ;
default [allow] ;
} ;
Adds martian addresses to the list of martian addresses. You can specify
the allow parameter to explicitly allow a subset of a range that was
disallowed. (See the section on "Route Filtering" in gated.control(4) for
more information on specifying ranges.)
Sample Definition Statements
The following is an example of definition statements for a system:
options gendefault ;
autonomoussystem 249 ;
interface 128.66.12.2 passive ;
martians {
0.0.0.26
};
A description of each statement in this example follows:
· The options statement tells the system to generate a default route
when it peers with an EGP or BGP neighbor.
· The autonomoussystem statement tells gated to use AS number 249 for
EGP and BGP.
· The interface statement tells gated not to mark interface 128.66.12.2
as down even if it sees no traffic.
· The martians statement prevents routes to 0.0.0.26 from ever being
accepted.
EXAMPLES
Sample Host Configurations
The gated.conf file for end systems is simple, usually containing only two
configuration statements.
1. The following sample configuration file emulates routed, runs RIP, and
only sends updates if there is more than one interface up and IP
forwarding is enabled in the kernel:
#
rip yes ;
#
Note that RIP will not run if UDP checksums are disabled in the
kernel.
2. The following sample gated.conf file runs RIP in quiet mode; it only
listens to packets, no matter how many interfaces are configured:
#
rip yes ;
{
nobroadcast ;
} ;
#
3. The following sample gated.conf file is suitable for any system that
runs RIP and has only one network interface:
#
# do not time-out the network interface
#
interface 136.66.12.2 passive ;
#
# enable rip
#
rip yes ;
#
The passive keyword prevents gated from changing the preference of the
route to this interface if it is believed to be down due to lack of
received routing information. The interface passive statement
identifies a router with a guest host on an Ethernet.
In the previous example, the route is through the directly attached
network interface. Normally when gated thinks an interface is down,
it removes it from the routing database to prevent a gateway from
announcing that it can route data through a nonoperational interface.
If the host has only one interface, it should not be removed from the
routing database even if the interface is down (the interface
136.66.12.2 passive statement in the example. RIP is enabled with
the rip yes statement. This statement is not required as it is the
default, but the explicit statement in the gated.conf file serves to
document the configuration to prevent future confusion.
Sample Interior Gateway (Intra-Domain) Configurations
Gateway configurations are more complicated than a simple host
configuration as gateways have multiple interfaces and may run multiple
protocols. This section contains sample gated.conf files for the following
interior gateway configurations:
· RIP only (subnet to backbone)
· RIP with default announcement
· Direct routes
· Static routes
· Importing routes
· Exporting routes
· CIDR
· Source and trusted gateways
· OSPF Using NBMA Mode
· RIP and OSPF
RIP only (subnet to backbone)
The following sample gated.conf file connects two networks within an
autonomous system. You can use this configuration file for any gateway
that uses only RIP and that connects a single subnet to a larger network.
#
# enable rip
#
rip yes ;
#
# using rip, announce subnet 3 via interface 136.66.1.2
#
export proto rip interface 136.66.1.2
{
proto direct
{
announce 136.66.3.0 metric 0 ;
} ;
} ;
#
# using rip, announce all routes learned from interface 136.66.1.2
#
export proto rip interface 136.66.3.1
{
proto rip interface 136.66.1.2
{
announce all ;
} ;
} ;
In this example, the first export statement tells gated to announce, via
the RIP protocol and interface 136.66.1.2, a direct route to subnet
136.66.3.0. The second export statement announces to subnet 3 all routes
learned from the interface 136.66.1.2, including subnet routes and any
routes to the rest of the world, as well as default routes.
The first export statement is not required because by default gated
announces every network that is directly connected to the gateway. The
export statement was explicitly entered for two reasons: to document the
intended structure and to avoid relying on defaults that might be changed
in future releases.
In any export statement, the main proto clause and the main interface
clause may define the protocol and interface through which the routes are
advertised. Subsidiary proto and interface clauses define the protocols
and the interfaces from which the routes must be learned.
RIP with default announcement
In the following sample gated.conf file, the gateway announces a default
route to the backbone and announces all of the individual subnet routes to
the outside world.
#
# enable rip
#
rip yes ;
#
# using rip, announce all local subnets via 136.66.12.3
#
export proto rip interface 136.66.12.3 metric 3
{
proto rip interface 136.66.1.5
{
announce all ;
} ;
};
#
# using rip, announce default to the local backbone via 136.66.1.5
#
export proto rip interface 136.66.3.1
{
proto rip interface 136.66.12.3
{
announce 0.0.0.0 ;
} ;
} ;
The first export statement statement explicitly directs gated to announce
all of the routes it learns from interface 136.66.1.5 out through interface
136.66.12.3. The explicit announce all is not required. The metric value
is specified in the main statement and applies to every route announced via
this protocol and interface. When the metric is specified in the export
clause, it only applies to the routes specified in that clause. In the
previous example, metric 3 applies to every route announced over interface
136.66.12.3 via RIP.
Direct Routes
If a gateway has interfaces on several networks, the following
configuration provides for announcing routes learned via the RIP protocol
and routes to the directly connected networks.
#
# enable rip
#
rip yes;
#
# using rip announce all directly connected networks with a metric of 0
# and all routes learned via the rip protocol
#
export proto rip {
proto direct {
all metric 0;
};
proto rip {
all;
};
};
Static Routes
The following configuration shows how to statically configure certain
routes to point to a particular gateway. Only routes learned via the RIP
protocol and the statically configured routes are announced.
#
# enable rip
#
rip yes;
#
# these networks and host are reachable via gateway 192.168.12.1
#
static {
host 192.168.2.1 gateway 192.168.12.1;
192.168.10.0 mask 255.255.255.0 gateway 192.168.12.1;
192.168.11.0 masklen 24 gateway 192.168.12.1;
};
#
# export via RIP all the statically configured routes and
# all routes learned via RIP
# the metric only applies to the static routes
#
export proto rip metric 1 {
proto static {
all;
};
proto rip {
all;
};
};
Importing Routes
The following configuration imports routes from the specified gateways.
You might want to do this when you only want to import routes if they meet
certain requirements supplied by a route filter.
#
# enable rip
#
rip yes;
#
# import via RIP routes only from these hosts (gateways)
#
import proto rip {
host 192.168.10.1;
host 192.168.11.1;
host 192.168.12.1;
}
Exporting Routes
The following configuration demonstrates how to filter out certain routes
from being announced:
#
# enable rip
#
rip yes;
#
# use the export statement to block out the 14, 15, and 16
# networks and announce all others
#
export proto rip {
192.168.14.0 masklen 24 restrict;
192.168.15.0 masklen 24 restrict;
192.168.16.0 masklen 24 restrict;
all;
}
CIDR
Because RIP version 1 does not carry netmask information in its packets,
CIDR is difficult, if not impossible, to convey in RIP version 1 packets.
The following configuration RIP version 2 is used to Multicast its routes.
RIP version 2 in RIP version 1 compatibility mode is not enough. While the
netmask information is provided in RIP version 1 compatible packets, routes
that might be improperly interpreted by RIP version 1 will not be
broadcasted by RIP version 2.
#
# enable rip
# turn on broadcast (RIPv2 will not multicast or broadcast without this)
# turn on version 2 multicast on each interface
#
rip yes {
broadcast;
interface 192.168.10.1 version 2 multicast;
interface 192.168.11.1 version 2 multicast;
};
Source and Trusted Gateways
Sometimes you do not want a RIP speaker to broadcast or Multicast (in the
case of RIP version 2) its route announcements. The following
configuration shows how to use the sourcegateways option to unicast the
packets. It also shows how to use the trustedgateways option.
#
# enable rip
# Send to 10.1, 11.1, and 12.1 but only accept from 10.1 and 11.1
#
rip yes {
nobroadcast;
sourcegateways 192.168.10.1 192.168.11.1 192.168.12.1;
trustedgateways 192.168.10.1 192.168.11.1;
};
OSPF Using NBMA Mode
In the following sample gated.conf file, a server is configured as both the
area border router and the backbone router. This example has two areas
(0.0.0.1 and 0.0.0.2) besides the OSPF backbone area. In area 0.0.0.1, one
other router (interface at 196.1.1.2) is eligible across the NMBA network
to be polled every 30 seconds. In area 0.0.02, two other routers are listed
(194.1.1.2 and 194.1.1.1), only one other router can engage in OSPF packets
with this router (194.1.1.2).
In the backbone area, all routers are polled by default at interval 30.
traceoptions parse ;
routerid 195.1.1.2 ;
#
RIP no ;
OSPF yes {
defaults {
preference 10 ;
cost 5 ;
type 1 ;
} ;
area 0.0.0.1 {
networks {
195.1.1.0 ;
} ;
interface 195.1.1.2 nonbroadcast {
routers {
195.1.1.1 eligible ;
195.1.1.2 eligible ;
} ;
priority 15 ;
enable ;
hellointerval 30 ;
routerdeadinterval 30 ;
pollinterval 30 ;
} ;
} ;
area 0.0.0.2 {
networks {
193.2.1.0 ;
194.1.1.0 ;
} ;
interface 194.1.1.3 nonbroadcast {
routers {
194.1.1.2 eligible ;
194.1.1.3 eligible ;
194.1.1.1 ;
} ;
priority 15 ;
enable ;
hellointerval 30 ;
routerdeadinterval 30 ;
retransmitinterval 30 ;
pollinterval 30 ;
} ;
} ;
backbone {
interface 15.13.115.156 nonbroadcast {
enable ;
transitdelay 20 ;
priority 10 ;
hellointerval 30 ;
routerdeadinterval 30 ;
retransmitinterval 30 ;
pollinterval 30 ;
} ;
} ;
} ;
RIP and OSPF
The following sample gated.conf file for AS 283 enables both RIP and OSPF
protocols and can be used for testing RIP and OSPF.
#options noinstall ;
interfaces {
interface le0 passive ;
} ;
autonomoussystem 283 ;
snmp yes ;
rip yes {
broadcast ;
defaultmetric 5 ;
interface le version 2 multicast ;
} ;
ospf yes {
traceoptions lsabuild protocol ;
monauthkey "ZZZZZZZZ" ;
backbone {
interface all {
priority 2 ;
} ;
interface le {
auth simple "YYYYYYYY" ;
} ;
} ;
} ;
static {
default gateway 132.236.200.200 preference 140 retain ;
}
In the RIP version 2 case, multicast packets are generated on all Ethernet
interfaces (for example, le0, le1, and so on). This is a safe way to test
RIP because the production gateways on this network do not support RIP
version 2. In the OSPF case, all interfaces are configured to be Priority
2, so the Proteon routers (Priority 0) become designated routers. A simple
password is specified "YYYYYYYY" for authentication of all Ethernet
interfaces (the only kind of interfaces in this configuration).
Sample Exterior Gateway (Inter-Domain) Configurations
This section contains sample gated.conf files for the following exterior
gateway configurations:
· RIP and EGP
· BGP and OSPF
RIP and EGP Configuration
The following sample gated.conf file enables both an interior (RIP) and an
exterior (EGP) protocol and sets certain protocol-specific parameters:
# generate a default route if an EGP neighbor is acquired
#
options gendefault ;
#
# define the autonomous system number for EGP
#
autonomoussystem 303 ;
#
# enable RIP
#
rip yes ;
#
# enable EGP with hello interval 1 1/2 minute, poll
# interval 10 minutes, neighbors 26.6.0.103 and 26.20.0.72
#
egp yes {
packetsize 24488 ;
group minhello 1:30 minpoll 10:00 {
neighbor 26.6.0.103 ;
neighbor 26.20.0.72 ;
} ;
} ;
#
# announce 136.66 to AS 183
#
export proto egp as 183 {
proto direct {
136.66 metric 0 ;
} ;
} ;
#
# announce default via RIP with a metric of 3
#
export proto rip interface 136.66.12.1 {
proto default {
announce 0.0.0.0 metric 3 ;
} ;
} ;
The AS number 303 is defined early because it is a definition statement and
must occur before the first protocol statement. EGP is enabled by the yes
keyword in the EGP statement, which also defines the following EGP
parameters: the packetsize parameter, defining the initial size of update
packets accepted; the group clause, setting parameters for all of the EGP
neighbors in the group; and minhello and minpoll, setting the protocol
timers.
The first export statement directs gated to use EGP to advertise the
network (136.66.0.0) to the Internet. This is the address of the network,
not of a gateway. The second export statement is used to announce the
default route to subnet 136.66.12.0 with a metric of 3.
BGP and OSPF Configuration
The following sample gated.conf file implements the transformation of
distance metrics between the internal (OSPF) and external (BGP) protocols.
Autonomous system 1019, of which gated is a member, contains network
19.0.0.0. The gated machine has several interfaces into this autonomous
system. The gated daemon is using BGP to peer with AS 2021, neighbor
21.5.1.21.
/etc/gated.conf
# # # # # # # # # # # # # # # # # # #
interfaces {options all passive; };
autonomoussystem 1019;
routerid 19.1.1.18;
rip no;
hello no;
egp no;
bgp yes {
preference 50 ;
group type
External peeras 2021
{
peer 21.5.1.21
;
} ;
group type
IGP peeras 1019
{
peer 19.1.1.19
;
} ;
} ;
ospf yes {
area 0.0.0.2 {
authtype none;
networks {
119.0.0.0 mask 255.0.0.0 ;
} ;
interface 119.2.128.18
cost 1 {
retransmitinterval 5;
transitdelay 1;
priority 1;
hello interval 10;
routerdeadinterval 40;
} ;
interface 119.4.128.18
cost 1 {
retransmitinterval 5;
transitdelay 1;
priority 1;
hellointerval 60;
routerdeadinterval 180;
} ;
} ;
backbone {
authtype none;
interface 19.1.1.19
cost 1 {
retransmitinterval 5;
transitdelay 1;
priority 1;
hellointerval 60;
routerdeadinterval 180;
} ;
} ;
} ;
export proto ospfase type 1 {
proto bgp as 2021 {
ALL
metric 1; };
proto direct {
ALL
metric 1; };
} ;
export proto bgp as 2021 {
proto direct {
ALL
metric 1; } ;
proto ospfase {
ALL
metric 1; } ;
} ;
In this example, two autonomous systems (one internal, one external) are
directly connected through a router that is attached to a backbone speaking
OSPF. The AS number 1019 is defined early as it is a definition statement
that occurs again in the first protocol statement, which enables BGP. The
first export statement directs gated to advertise routes from the internal
group AS 1019 running OSPF as the IGP gathering routing information to the
external group AS 2021 using BGP.
Routes to two local Ethernets in AS 1019, identified as 119.2.128.18 and
119.4.128.18 (119.0.0.0 mask 255.0.0.0), are advertised along with the OSPF
backbone (19.1.1.19). The parameters for AS path, path origin, and
transitive optional attributes, including transmission intervals, are
defined. The second export statement announces the default route to AS
2021 with a metric of 1.
SEE ALSO
Daemons: gated(8)
Files: gated.control(4), gated.proto(4)
Networking: gated_intro(7)
RFC 827, Exterior Gateway Protocol EGP, E. Rosen
RFC 891, DCN local-network protocols, D. Mills
RFC 904, Exterior Gateway Protocol Formal Specification, D. Mills
RFC 1058, Routing Information Protocol, C. Hedrick
RFC 1105, Border Gateway Protocol BGP, K. Lougheed, Y. Rekhter
RFC 1163, A Border Gateway Protocol (BGP), K. Lougheed, Y. Rekhter
RFC 1164, Application of the Border Gateway Protocol in the Internet, J.
Honig, D. Katz, M. Mathis, Y. Rekhter, J. Yu
RFC 1227, SNMP MUX Protocol and MIB, M. Rose
RFC 1245, OSPF Protocol Analysis, J. Moy
RFC 1246, Experience with the OSPF Protocol, J. Moy
RFC 1253, OSPF Version 2 Management Information Base, F. Baker, R. Coltun
RFC 1256, ICMP Router Discovery Messages, S. Deering
RFC 1265, BGP Protocol Analysis, Y. Rekhter
RFC 1266, Experience with the BGP Protocol, Y. Rekhter
RFC 1267, A Border Gateway Protocol 3 (BGP-3), K. Lougheed, Y. Rekhter
RFC 1268, Application of the Border Gateway Protocol in the Internet, P.
Gross, Y. Rekhter
RFC 1269, Definitions of Managed Objects for the Border Gateway Protocol
(Version 3), J. Burruss, S. Willis
RFC 1321, The MD5 Message-Digest Algorithm, R. Rivest
RFC 1370, Internet Architecture Board Applicability Statement for OSPF
RFC 1388, RIP Version 2 Carrying Additional Information, G. Malkin
RFC 1397, Default Route Advertisement In BGP2 And BGP3 Versions Of The
Border Gateway Protocol, D. Haskin
RFC 1403, BGP OSPF Interaction, K. Varadhan
RFC 1583, OSPF Version 2, J. Moy
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