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

Miles Lott mlott at gie.com
Mon Jan 7 15:46:19 CET 2013

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

We use Centos.  But, it wouldn't have occurred to me to put two network 
cards on the same physical network and VLAN unless they were bonded.  
Our private connection is on a separate network - actually a couple of 
cables interconnected between the servers.

On 01/04/2013 09:09 PM, Nik Martin wrote:
> I can't see how this is a Drbd issue, as arp is somewhere down in layer two, so taking it out on Drbd may make you feel better but it's probably not going to actually fix anything. Have you posted this to a Centos list? Lots of network internals were in a state of change between 5.7 and 6.0 in Centos (or RHEL) since rh switched to the abomination that is network manager.
> Regards,
> Nik
> Gavin Henry<gavin.henry at gmail.com>  wrote:
>>> 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
>>> recipe?
>>> 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.
>>> Thanks,
>>> Gavin.
>> Couldn't get this to work so have had to bin DRBD. Shame.
>> Thanks.
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