Ping and FTP Resolve IP Address with Leading Zero as Octal (115388)

MORE INFORMATION

Many TCP/IP programs such as Ping and FTP use the inet_addr() sockets function to translate IP address strings into 4-byte addresses. This function accepts an IP address in standard decimal, octal, and hexadecimal notation, such that the following IP address examples are acceptable to Ping and FTP and resolve to the same IP address:

   22.101.31.153 (decimal)
   026.0145.037.0231 (octal)
   0x16.0x65.0xF1.0x99 (hexadecimal)
   0x16.101.037.153 (a combination of all three number systems)
				

If you unintentionally enter a leading zero in an octet, the IP address that Ping and FTP resolve is not the same as you intended, as in the following example (using Ping):

   In Windows NT 3.1:

      c:\>ping 022.101.31.153
      Pinging host 022.101.31.153 (unnamed) : 18.101.31.153
      ICMP Echo Reply:TTL 32
      ICMP Echo Reply:TTL 32
      ICMP Echo Reply:TTL 32
      ICMP Echo Reply:TTL 32
      Host 022.101.31.153 replied to all 4 of the 4 pings


   In Windows NT 3.5:

      c:\>ping 022.101.31.153
      Pinging 18.101.31.153 with 32 bytes of data:
      Ping succeeded: 32 bytes time=10ms TTL=32
      Ping succeeded: 32 bytes time=10ms TTL=32
      Ping succeeded: 32 bytes time=10ms TTL=32
      Ping succeeded: 32 bytes time=10ms TTL=32
				

NOTE: In this example, 022.101.31.153 is resolved by Ping to be 18.101.31.153 decimal, not 22.101.31.153 decimal.

This results in either a successful (shown above) or unsuccessful verification of the wrong IP address, depending on whether the resolved IP address is a valid IP address in your network environment.

Windows NT 4.0 Enterprise Cluster Administrator will give the following error if you specify an ip address to connect to the cluster with leading zeroes on the decimal octet, you may get the following error:

"A connection to the cluster at "022.101.31.153" could not be opened. This may be caused by the customer on node "022.101.31.153" not being started. Would you like Cluster Administrator to attempt to start the Cluster Service on node "022.101.31.153"."



To avoid an address being incorrectly resolved, it is recommended that you check for and remove leading zeros, unless an octal number is intended.

The following utilities also exhibit this behavior:

PING
FTP
TELNET
Internet Explorer (IE)
Microsoft Cluster Adminitrator
Microsoft Cluster Setup Wizard