Procurve 5308XL and DHCP server

[andrea vian]

Hallo again!
With a Procurve 5308XL, is it possible to avoid a DHCP server to lease IP addresses out of its subnet?
Thanks!
Andrea

[Michael Davis_9]

DHCP relaying is turned on by default, but you can turn it on with the following CLI argument:
HPswitch(config)# no dhcp-relay

I got this from the manuals on the CD that came with the switch. 5300XL Switches, Management and Configuration Guide, chapter 16 pages 74 and 75.

[Michael Davis_9]

Err, I mean, turn it off with the CLI...

[Stuart Teo]

I believe that dhcp-relay is not the solution.

To ask a L2 switch not to forward a frame when it contains a dhcp-request is not possible. But the 5308xl is a L3 switch.

A dhcp-request starts with a udp packet from 255.255.255.255 to 0.0.0.0. If you set up your 5308xl with an ACL that blocks that, then it would effectively block dhcp-servers from hearing the requests. This should suffice for your purpose but remember that dhcp is a huge subject on itself.

dhcp-relay is used when there is an off subnet dhcp-server and you are using your 5308xl as a router to relay dhcp-requests.

[Stuart Teo]

Another way would be to block ports 67 & 68. I personally am against the use of ACLs. Just so that you know my position. ;)

[Ardon]

Andrea,

The use of No DHCP-Relay I would avoid as that is a box wide command and would also impact VLANs where you do want to use DHCP on. No need to use ACLs. If there is an IP Interface of that particular VLAN and no IP-Helper, DHCP Broadcasts will not be forwarded anyways.

Thanks, Ardon

[andrea vian]

Ardon,
thanks for your reply.
I've got a simple-default configuration, with no VLAN and software version E.07.27.
Please, can you point me to documentation and procedures to do so?
Thanks!
Andrea