Router failover not detecting outside interface link lost

Question

Suppose I have two routers configured in master/slave configuration.

They look something like this (addresses are not real ones)

123.123.123.10  <===> [eth0] Router 1 (10.1.1.2) [eth1] ===> +----------+
                                                             | 10.1.1.1 | ===> LAN
172.123.123.10  <===> [eth0] Router 2 (10.1.1.3) [eth1] ===> +----------+

The 10.1.1.1 is the default route for the Network (10.1.1.0). What's slightly different in this config to other's I've seen is that I don't have an external virtual IP. Also, the 10.1.1.1 addresses are in real life, public IP's (not private ones shown here). This is more of a router setup than a firewall setup so I'm not using NAT here.

Now the issue that I'm having is that I can't see any way to configure UCARP or VRRP to monitor both eth0 & eth1 and fail over to the backup router should either of them go down. What I'm seeing is that if Router1 is the master and I unplug eth0 on router1, it doesn't fail over to router 2. However, it will if instead I unplug eth1 of router 1.
In VRRP I see there is a cluster group, but it seems that for this to work you need to have virtual ip's or vrrp instances rather than actual interfaces assigned to it.

I hope my explanation is clear. How do I get around this?

If the link is lost, the route out the interface should be lost too. It should be possible to make VRRP track a particular route so that if a router has no direct route to a particular destination, it does not claim the VRRP IP. (What VRRP program are you using?) But you shouldn't need to do this anyway. If router 1 has no direct route, it should use router 2's route anyway -- even with static routing. — David Schwartz, Nov 14 '12 at 04:29
Thanks. I might try VRRP (keepalived) again. UCARP certainly isn't working as I would like in this situation. — hookenz, Nov 15 '12 at 00:18
UCARP should also have an option to track the status of an interface or route. What program are you using? — David Schwartz, Nov 15 '12 at 00:19
I notice vrrp has an option track_interface which looks to be what I want. The only issue I'm having with that is now is that vrrp isn't bringing up the virtual IP and no errors are shown in the logs. — hookenz, Nov 15 '12 at 01:58
ok I fixed that, it was a config typo. by the way ucarp has support for long mac addresses i.e. infiniband. do you know if keepalive has that feature? — hookenz, Nov 15 '12 at 02:52

hookenz · Accepted Answer · 2012-11-15T05:42:58.530

To answer my own question. I eventually found the answer buried in a little documented config file. (Pity the keepalived documention is so out of date, yet the product is still be developed and works very well)

vrrp_instance default {
  virtual_router_id 1
  interface eth2
  priority 50
  track_interface {
    eth0
    eth1
  }
  virtual_ip_address P
    10.1.1.1/24 brd 10.1.1.255 dev bond0 label bond0:vrrp
  }

  #... other config ...
}

The key here is the track_interface. It says that keepalived will monitor the link state of eth0 and eth1 when deciding to fallback. It'll move the node into the fault state.

Router failover not detecting outside interface link lost

1 Answers1