IBM 6611 Routers May Generate Invalid DHCP Frames (156974)

SYMPTOMS

Your Dynamic Host Configuration Protocol (DHCP) clients that are on the opposite side of an IBM 6611 router from their DHCP Server may receive one of the following error messages when they attempt to lease an IP address:

Windows NT DHCP Client

The DHCP client could not obtain an IP address.
If you want to see DHCP messages in the future, choose YES, otherwise choose NO.

Windows 95 DHCP Client

This DHCP client was unable to obtain an IP network address from a DHCP server.

CAUSE

Some versions of software for the IBM 6611 router create and forward invalid frames when the router is acting as an RFC 1542 BOOTP relay agent. Specifically, the frames are invalid because their IP header contains a Source IP Address of 0.0.0.0, rather than the IP address of the router.

These invalid frames are silently discarded by the Windows NT TCP/IP stack and are not passed to the DHCP service on the server.

RESOLUTION

To correct this problem, contact IBM and request an upgrade to the IBM 6611 router software.

The product included here is manufactured by a vendor independent of Microsoft; we make no warranty, implied or otherwise, regarding the product's performance or reliability.

MORE INFORMATION

Per section 4.2.2.11 of RFC 1812 (Requirements for IP Version 4 Routers), a Source IP Address of 0.0.0.0 "MUST NOT be used as a source address by routers, except the router MAY use this as a source address as part of an initialization procedure (for example, if the router is using BOOTP to load its configuration information)."

In the situation described here, the IBM 6611 router is not in the process of determining its own configuration, and therefore, the frames it generates with a Source IP Address of 0.0.0.0 are invalid.