[c-nsp] cisco-nsp Digest, Vol 74, Issue 20

Chris Burwell cburwell at gmail.com
Fri Jan 9 18:30:58 EST 2009


Hi Eric,

There are a few basic things that should be checked first. I don't
mean to insult anyone, but I sometimes overlook some simple steps when
I dive into a problem.

First, ensure you have the latest software (as HP calls it) running on
the switch. This is freely available from the Procurve website (no
login is needed).

Second, console into the switch and see if you can ping the DHCP
server from the command prompt. If you cannot, then the switch does
not know how to reach the DHCP server.

Finally, check to see that you have the proper route for the VLAN on
the switch. For example on our core 8212zl, I have to add the
following statement for each VLAN:

vlan 800
    ip ospf 192.168.0.1 area 0.0.0.1
exit

Obviously this is the statement used for OSPF on an 8212zl, so your
config might be different (particularly if you're using a different
routing protocol.

- Chris

> Date: Thu, 8 Jan 2009 13:52:50 -0800
> From: "Eric Cables" <ecables at gmail.com>
> Subject: [c-nsp] Procurve DHCP relay question
> To: "cisco-nsp at puck.nether.net" <cisco-nsp at puck.nether.net>
> Message-ID:
>        <d5c7ccac0901081352w1e492fadg61d3edbdc1fcc67c at mail.gmail.com>
> Content-Type: text/plain; charset=ISO-8859-1
>
> I'm in the middle of a transition from HP -> Cisco, with an HP 2848 as the
> "core", so sorry if this e-mail is off topic.  I am having a hard time
> getting DHCP relay to work, and was hoping someone with HP experience could
> chime in with some assistance.
>
> I've created a new VLAN, and have specified a helper-address to point to a
> DHCP server that manages dozens of scopes.  The new VLAN functions fine,
> assuming users are given a static address, but DHCP does not appear to work
> at all.
>
> To troubleshoot I pointed the helper-address to a system with Wireshark, but
> I don't see any requests coming in when a user on the new VLAN requests a
> new DHCP address, indicating that the request is not being forwarded
> properly.  Is there any debugging available on the procurve to troubleshoot
> this further?
>
> I've read a number of documents describing how to configure DHCP relay on a
> procurve, and as far as I can tell the recommendations match my
> configuration.
>
> Here are the features enabled on the 2848:
>  - 'ip routing' is enabled
>  - 'dhcp-relay' does not show in a 'show run', indicating it is enabled (the
> default)
>  - A 'ip helper-address x.x.x.x' statement is configured on the VLAN
> interface
>  - There is a route back to the destination helper-address
>  - Connectivity works on the VLAN in question, assuming users are statically
> configured
>
> Any advice would be appreciated..
>
> -- Eric Cables


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