[c-nsp] DHCP Relay breaks after some time on Cat 3750X

[Markus Hauschild]

Just a quick follow up:

After upgrading from 15.2(1)E to 15.2(3)E2 the issue has not appeared
again (no config changes have been made since).


Markus

On Fri, Aug 28, 2015 at 5:19 AM,  <frnkblk at iname.com> wrote:
> Reminds me of this recent thread:
> https://puck.nether.net/pipermail/cisco-nsp/2015-August/100245.html
>
> Frank
>
> -----Original Message-----
> From: cisco-nsp [mailto:cisco-nsp-bounces at puck.nether.net] On Behalf Of
> Markus Hauschild
> Sent: Thursday, August 27, 2015 6:07 AM
> To: cisco-nsp at puck.nether.net
> Subject: [c-nsp] DHCP Relay breaks after some time on Cat 3750X
>
> Hi,
>
> I have a weird problem with DHCP relay on a Cat 3750X:
>
>
> Configuration is as follows (full config w/o passwords in attachment):
>
> Two "ip helper-address <ip>" statements (one for each server) are set
> on each vlan interface where I want to have DHCP relay.
>
>
> After I boot the switch DHCPDISCOVER broadcasts from clients are
> properly forwarded to both DHCP servers (example output taken from the
> first one):
>
> Aug 26 17:49:57 aveta dhcpd: DHCPDISCOVER from 60:57:18:x:y:z via
> 172.23.4.254
> Aug 26 17:49:58 aveta dhcpd: DHCPOFFER on 172.23.4.240 to
> 60:57:18:x:y:z ($hostname) via 172.23.4.254
> Aug 26 17:49:58 aveta dhcpd: DHCPREQUEST for 172.23.4.240 (172.23.2.1)
> from 60:57:18:x:y:z ($hostname) via 172.23.4.254
> Aug 26 17:49:58 aveta dhcpd: DHCPACK on 172.23.4.240 to 60:57:18:x:y:z
> ($hostname) via 172.23.4.254
>
> Yet after a while DHCPDISCOVER broadcasts are no longer forwarded to
> any DHCP server, only unicast (e.g. DHCPREQUEST) still works.
>
> I had a similar config running for months (obviously a few times
> port/vlan assignments changed, I migrated from OSPF+OSPFv3 to OSPFv3
> only ...) until I had this problem occur for the first time.
>
> The current situation is that DHCP relay works for a certain period of
> time (hours to days) after a cold boot until all DHCP broadcasts are
> silently discarded again.
>
> I do see the broadcasts on wireshark in the same VLAN, I don't see any
> DHCPDISCOVER on the server with tcpdump.
>
>
> I tried debug ip dhcp server packet but couldn't find anything
> helpful. Any ideas what to further debug/look into? Anything wrong
> with the config? Possible Hardware problem?
>
>
> Greetings,
> Markus
> _______________________________________________
> cisco-nsp mailing list  cisco-nsp at puck.nether.net
> https://puck.nether.net/mailman/listinfo/cisco-nsp
> archive at http://puck.nether.net/pipermail/cisco-nsp/
>
>