Static Routing : 4. Floating Static Route

Static routes have a very low administrative distance of 1, this means that your router will prefer a static route over any routes that were learned through a dynamic routing protocol. If we want to use a static route as a backup route, we’ll have to change its administrative distance. This is called a floating static route.

A floating static route is a static route with an administrative distance higher than that of the routing protocol in use. In this way, the floating static route will only appear in the routing table if the dynamically learned route is lost.

Floating Static Route

R1:

R1#configure terminal

Enter configuration commands, one per line.  End with CNTL/Z.

R1(config)#ip route 40.0.0.0 255.0.0.0 30.0.0.2 1

(Primary Route: AD value is 1, So this Route will be selected to Reach the destination 40.0.0.0)

R1(config)#ip route 40.0.0.0 255.0.0.0 20.0.0.2 2

(Backup Route: AD value is 2, If primary route fails, this route will work)

R2:

R3#configure terminal

Enter configuration commands, one per line.  End with CNTL/Z.

R3(config)#ip route 10.0.0.0 255.0.0.0 30.0.0.1 1

(Primary Route: AD value is 1, So this Route will be selected for reply packet to Reach the Source 40.0.0.0)

R3(config)#ip route 10.0.0.0 255.0.0.0 20.0.0.1 2

(Backup Route: AD value is 2, If primary route fails, this route will work)

R1:

R1#show ip route

Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP

       D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area

       N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2

       E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP

       i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS-IS inter area

       * - candidate default, U - per-user static route, o - ODR

       P - periodic downloaded static route

Gateway of last resort is not set

C    10.0.0.0/8 is directly connected, FastEthernet0/0

C    20.0.0.0/8 is directly connected, Serial3/0

C    30.0.0.0/8 is directly connected, Serial2/0

S    40.0.0.0/8 [1/0] via 30.0.0.2 (Showing only Primary Route)

Now Primary Route Failed

R1:

R1#show ip route

Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP

       D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area

       N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2

       E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP

       i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS-IS inter area

       * - candidate default, U - per-user static route, o - ODR

       P - periodic downloaded static route

Gateway of last resort is not set

C    10.0.0.0/8 is directly connected, FastEthernet0/0

C    20.0.0.0/8 is directly connected, Serial3/0

S    40.0.0.0/8 [2/0] via 20.0.0.2 (Now the floating static route appearing in the routing table after primary route failed.)