On 02/01/2012 04:06 PM, Les Mikesell wrote: > On Wed, Feb 1, 2012 at 1:35 PM, Steve Clark<sclark at netwolves.com> wrote: >>> I'm wanting to configure a CentOS 6 server to have a fall-back default route via >>> a second network interface. >>> >>> Given: >>> >>> - eth0 with 192.168.0.10 on subnet 192.168.0.0/24 gateway 192.168.0.1 >>> - eth1 with 192.168.1.10 on subnet 192.168.1.0/24 gateway 192.168.1.1 >>> >>> Where eth0's network is a "back door" to the internet, and eth1's is the "front >>> door", I believe I can configure the routing table manually like this: >>> >>> ip route default scope global \ >>> nexthop via 192.168.1.1 dev eth1 weight 1 \ >>> nexthop via 192.168.0.1 dev eth0 weight 2 >>> >>> However, I've re-read the RHEL6 documents for configuring static routes here: >>> >>> >>> http://docs.redhat.com/docs/en-US/Red_Hat_Enterprise_Linux/6/html/Deployment_Guide/s1-networkscripts-static-routes.html >>> >>> This kind of thing doesn't seem to fit into the scheme of >>> /etc/sysconfig/network-scripts/route-eth? described there, since the route isn't >>> "for" any single interface. Is there a "RHEL/CentOS" way to do this, or do I >>> need to resort to some sort of script containing the above ip route command >>> inserted somewhere? >>> >>> And how do I stop CentOS from trying to pick its own default gateway settings >>> (since /etc/sysconfig/network likely won't have a GATEWAY parameter)? >>> >>> >> Hmm... >> >> I just tried this and besides needing ip route "add" default >> >> It does not seem to work when I unplug the cable on my primary link. > I don't think CentOS is smart enough to automatically drop routes > associated with a NIC that is down like a Cisco would. If you put > routes in /etc/sysconfig/network-scripts/routes-eth? to match the > device names, the ifup and ifdown scripts will add/remove routes when > you manually run time to enable/disable a particular NIC, but that > doesn't get you automatic failover. And with ethernet type devices it > is pretty rare for the link to go away at the same time the packets > stop getting through anyway. > I got it sort of work - but even with the weights and flushing the routing cache sometimes it seemed to want to go on the higher weighted route. Could be something in my setup. I did onetime have if fail from the lower weight to the higher weighted route when I pulled the cable on the preferred route. -- Stephen Clark *NetWolves* Director of Technology Phone: 813-579-3200 Fax: 813-882-0209 Email: steve.clark at netwolves.com http://www.netwolves.com