Static route failover

[hmc2500]

Hi we have two WAN lines from different ISP's that connect 2 locations. Routes are added on the main L3 switches. We configured the 1gbps link with a default route 0.0.0.0 0.0.0.0 gw1 and the other link with 0.0.0.0 0.0.0.0 gw2 5 (note administrative distance is 5). It doesn't work and it looks like because the L3 switch cannot track if a remote gateway or route is offline. Now ip sla would probably fix this issue but we have a lot of cisco devices that have an older IOS running that does not support ip sla. IS there any other way I can configure this so failover will work without having to upgrade the IOS?

[Peter Paluch]

Hi Henry,

Unfortunately, if a dynamic routing protocol advertising the default route is not an option, then without IP SLA, the only property of the default route that the L3 switch is capable of validating is whether the next hop IP address can be resolved to a working egress interface.

Please note that in older IOSes, the IP SLA was called RTR, and the IOS used significantly different syntax:

http://www.cisco.com/c/en/us/td/docs/ios/12_2/configfun/configuration/guide/ffun_c/fcf017.html#wp1001466

Perhaps your L3 switches do support IP SLA under the older syntax.

Under circumstances (if both gw1 and gw2 are on the same network), these two gateways could perhaps be configured to operate as an HSRP standby group, backing each other. In that case, you would need just a single default route pointing to the virtual IP address of the group. This would be a workaround, however, as HSRP is not meant to be used this way.

Best regards,
Peter

[hmc2500]

THanks, I will look into rtr. We already have an HSRP and a third gateway configured on that network.