[DRBD-user] CentOS, eth0, eth1 and arpwatch flip flops

Gavin Henry gavin.henry at gmail.com
Wed Dec 26 11:05:30 CET 2012

Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.

Dear all,

Has anyone experienced this whilst running DRBD over eth1 between two
CentOS 5.7 servers?

eth1 is a private IP address, unroutable. eth0 is the public address.
CentOS will reply sometimes once every 3 days or every 14mins~ saying
"My public IP is on eth1" to arp requests when it's not, it's eth0.

This freezes traffic and causes issues. We've looked at arp*
/etc/sysctl.conf etc. and arptables, but wondered if anyone had a

We have this already which didn't help as it happened Christmas Eve
too as we kept eth1 up for a few days to test:

# For the dual interface - 06.12.12
net.ipv4.conf.eth0.arp_filter = 1
net.ipv4.conf.eth0.arp_ignore = 1
net.ipv4.conf.eth1.arp_filter = 1
net.ipv4.conf.eth1.arp_ignore = 1
net.ipv4.conf.all.arp_filter = 1

eth0 and eth1 are on the same VLAN/broadcast domain, but eth1 is a
169.xx and eth0 is a routable public IP.

We're having to shut eth1 down and bring it up for sync at night.



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