Friday, August 29, 2008

Multi-homing under IPFilter: A gotcha with HP-UX

In the last year I've been experiencing some weird problems under IP Filter when using multi-homed HP-UX servers. I've overcome this up until now but I think I have hit a particular problem when running under ServiceGuard and floating IPs.

Take the following steps if your TCP sessions lock up after a while, without any indication in the syslog that packets are being blocked:

1. Stop IP Filter (easy, but probably not what you want)

2. If running IP Filter with a multi-homed system, take great care to prevent any asymmetric routing (i.e. be sure that what gets in on one interface, gets out on the same).

I'll try to make a comprehensive post on this particular problem soon.

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