Static floating routing (Cisco)

Technology: Routing

Area: Static routing

Vendor: Cisco

Title: Floating Static Routing

Software: 12.X , 15.X, IP Services

Platform: Catalyst 3560, 3750, 3850, 4500, 6500, ISR/ASR Routers

In situation when a router has two identical routes the decision regarding which one gets installed in the routing table is based on the lowest administrative distance. With static routing, we can deliberately use this behavior as a basic redundancy mechanism by configuring a backup route with
a higher administrative distance than the primary route.

To configure floating static routing you need to specify the backup route with higher administrative distance value in our case it is a number of 10:

R1#configure terminal
R1(config)#ip route 100.10.20.0 255.255.255.0 172.16.1.1
R1(config)#ip route 100.10.20.0 255.255.255.0 10.1.0.2 10

Verification commands:

We can verify current state of our floating static route by using below command. The best path has an administrative distance equal one, however the non-active backup path has value of 10.

R1#show ip static route 100.10.20.0/24
Codes: M - Manual static, A - AAA download, N - IP NAT, D - DHCP,
G - GPRS, V - Crypto VPN, C - CASA, P - Channel interface processor,
B - BootP, S - Service selection gateway
DN - Default Network, T - Tracking object
L - TL1, E - OER, I - iEdge
D1 - Dot1x Vlan Network, K - MWAM Route
PP - PPP default route, MR - MRIPv6, SS - SSLVPN
H - IPe Host, ID - IPe Domain Broadcast
U - User GPRS, TE - MPLS Traffic-eng, LI - LIIN
Codes in []: A - active, N - non-active, B - BFD-tracked, D - Not Tracked, P - permanent

M  100.10.20.0/24 [1/0] via 172.16.1.1 [A]
M                 [10/0] via 10.1.0.2 [N]

Once in any reason the primary path goes done we can verify the network state with the same command and check if backup takes priority.

R1#sh ip static route 100.10.20.0/24
Codes: M - Manual static, A - AAA download, N - IP NAT, D - DHCP,
G - GPRS, V - Crypto VPN, C - CASA, P - Channel interface processor,
B - BootP, S - Service selection gateway
DN - Default Network, T - Tracking object
L - TL1, E - OER, I - iEdge
D1 - Dot1x Vlan Network, K - MWAM Route
PP - PPP default route, MR - MRIPv6, SS - SSLVPN
H - IPe Host, ID - IPe Domain Broadcast
U - User GPRS, TE - MPLS Traffic-eng, LI - LIIN
Codes in []: A - active, N - non-active, B - BFD-tracked, D - Not Tracked, P - permanent

M  100.10.20.0/24 [1/0] via 172.16.1.1 [N]
M                 [10/0] via 10.1.0.2 [A]