same AD paths

[a.hajhamad]

hello,

if I have two paths to reach a destination network the first path advertised by EIGRP and the second path configured as static route with AD 90 "ip route dst_NW dst_S/M next-hop 90".

since EIGRP AD is 90 and we configured the static route also as 90 which path the router preferred to use or it load-balance?

Thanks

[Martin Hruby · Accepted solution]

Hello

By default when you have two paths with the same administrative distance and the same metric, and both are present in the routing table, the router will perform equal-cost multipath (ECMP) load-sharing. The actual load-sharing method, whether per-flow (default) or per-packet depends on your platform and CEF configuration.

Since static routes will always have metric=0, as metric is related to dynamic routing protocol and used to find the least-cost path, when you configure a static route with AD=90 it will take precedence over the route learned via EIGRP due to lower metric.

R2#show ip route 1.1.1.1
Routing entry for 1.1.1.1/32
  Known via "static", distance 90, metric 0
  Routing Descriptor Blocks:
  * 10.0.0.1, via FastEthernet0/0
      Route metric is 0, traffic share count is 1

versus

R2#show ip route 1.1.1.1
Routing entry for 1.1.1.1/32
  Known via "eigrp 1", distance 90, metric 156160, type internal
  Redistributing via eigrp 1
  Last update from 10.0.0.1 on FastEthernet0/0, 00:00:02 ago
  Routing Descriptor Blocks:
  * 10.0.0.1, from 10.0.0.1, 00:00:02 ago, via FastEthernet0/0
      Route metric is 156160, traffic share count is 1
      Total delay is 5100 microseconds, minimum bandwidth is 100000 Kbit
      Reliability 255/255, minimum MTU 1500 bytes
      Loading 1/255, Hops 1

Best regards,
Martin

[Peter Paluch · Accepted solution]

Hello,

I have not been able to confirm this in official Cisco documentation but I recall Don Slice from Cisco once mentioning to me that if this situation happens, the router will internally fall back to the default administrative distances to decide which route is more preferred. In your case, the static route would win.

Best regards,
Peter