[CentOS] CentOS 5.7 eth0, eth1 and arpwatch flip flops

Wed Dec 26 19:44:50 UTC 2012
Gavin Henry <gavin.henry at gmail.com>

>> We're having to shut eth1 down and bring it up for sync at night.
> To what type of equipment are your ethernet devices connected?

I'm asking now.

> Are they
> both connected to the same device?

Same VLAN, not sure about same device yet. Checking.

> I've seen some devices (particularly
> 2Wire) that do not like two interfaces from the same system connected to
> them.

Reading the arp_filter settings it does match what we're experiencing, but I've
never seen it before, but haven't ever been looking for it. Maybe
because this is
SIP/RTP traffic vs normal data traffic which when the switch switches
the MAC <-> IP ARP mappings
the voice traffic drops.

You wouldn't noticed that on normal data traffic. arpwatch is picking
up the flip flops.

> You note that eth1 is on a 169.xx IP, and earlier in your email, you note
> that it's non-routable. Perhaps that's not the wording you wished, to use,
> or perhaps you meant that it's not routed out to the internet, however,
> 169.xxx.xxx.xxx is most certainly a "routable" IP block, as far as
> internet standards go.

You're right. We're using when we shouldn't be! It should
be either in the ranges
below or 169.254.x.x. Doh!

> The only "non-routable" (i.e. reserved for private networks) IP blocks are:
> -
> -
> -
> While certainly not an undertaking to be done lightly, you may wish to
> renumber your internal network.

For two DRBD interfaces this will be fine but will need an umount or
schedule reboot for the pair.