[c-nsp] DHCP relay still forwarding to old helper even if it's removed or changed

Jason Lixfeld jason at lixfeld.ca
Mon Jan 19 12:56:53 EST 2015

I’ve got a 4500/Sup7L-E running 3.3.2SG (15.1(1)SG2) with an SVI configured to use a DHCP relay (ip helper-address).

I tried to change the helper address, but after making the change, the box was still routing broadcasts to the old helper.

I’ve seen this once before and did a bunch of troubleshooting, but couldn’t find a workaround short of rebooting the box.  I went so far as to try and delete and recreate the SVI with the interesting helper config on it, but even still, it sends to the original helper address.

Has anyone seen anything like this in the wild before?  I know this is running really old code and I have a plan in the works to upgrade all the boxes running this version to 3.6E where this and a bunch of other bugs are fixed, but I’m hoping that I can effect some sort of a workaround for this particular issue until then.

Thanks in advance.

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