DHCP Relay and ip forward-protocol command

Hi All,

With srg's questions on DHCP, I've revisited dhcp relay and ran through some tests using "ip forward-protocol" command.  With GNS3 12.4 code, seeing that the command is neither sufficient nor necessay when using "ip helper-address" to forward DHCP packets to the server.  Only command necessary is "sevice dhcp".  Doesn't that contradict Usage Guidelines for ip helper-address?  Is this a bug in the my code?

I  turned on "debug ip udp" and didn't see any forwarding output.  Then disabled "ip forward-protocol" but still, dhcp relay forwards the discoveries to  server.

Guessing that the "ip forward-protocol udp bootps" is just that, to forward to a bootp server ?

Second note:  Vice ip helper-address, why not use a relay pool, which appears to not forward tftp, dns and such?  Again testing with GNS3

// RandyB



  • Hi,

    The command "service dhcp" allows the router to be a DHCP server, a DHCP relay-agent or both, and is the only command that controls these two functions. 

    If the "ip dhcp bootp ignore" command is configured, the router will NO longer reply to bootp requests as a BOOTP server, but can still forward these requests further if "ip helper-address" is configured and "ip forward-protocol udp bootpc" (about the forward-protocol requirement i'm not sure as i don't have a BOOTP client to test out).



  • Hi Chrisian and All,

    Thanks for the feedback.


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