How to allow only DHCP requests ?

[johnramz]

I am not certain if this is the case.

I configured 2 vlans in a 3750 switch and there 1 MS DHCP server for both. For the VLAN that is different to the network the DHCP server is on i used the "ip helper-address" command . This is working great however I am concerned about all the broadcasts coming from this VLAN to the DHCP server.

I would like to only allow DHCP requests anf nothing else from that VLAN. I tried "no ip forward-protocol" but it is not available for the 3750 looks like.

Thanks for your help

John

[IAN WHITMORE]

Hi John,

Why don't you try an ip directed-broadcast. The good thing is you can specify it with an extended access-list so you can filter by IP and port number. That might work. Haven't tried it myself though.

You can read about it in the command reference for 3750.

http://www.cisco.com/en/US/docs/ios/12_3t/ip_addr/command/reference/ip1_i1gt.html#wp1168114

HTH,

Ian

[johnramz]

Ian,

Interesting suggestion. It looks like I should enable it not on the svi(switch virtual interface) where the packets come from, but in the svi that belongs to the same subnet where the DHCP is located.

I'll give a try and post back.....

Thanks

John