Lab 20 – OSPF Path Influencing Using Cost

Prerequisites: CCNP level skills.
Pic. 1 – OSPF Topology.
Task 1

On R1 check the paths towards

Task 2
Manipulate the OSPF cost so R1 prefers R2 towards

Lab Solution

Task 1

OR1 check the paths towards
Changing the cost on Loopback interfaces does not influence the path selection. R2 is the DR (representative) providing access to what is advertised by the originator of the subnets and There is only ONE originator of these subnets unlike

Pic. 2 – R1 Routing Table.

Task 2

Manipulate the OSPF cost so R1 prefers R2 towards

Both R2‘s and R3 ‘s cost towards is 1 (auto-cost reference-bandwidth = 100,000,000/bandwidth of the F1/0 interface). R1’s cost of s0/0 = 64.

Pic. 3 – R2’s Cost to
Pic. 4 – R3 Cost to

R3 Configuration:

interface FastEthernet1/0
ip address
ip ospf cost 2


Pic. 5 – R1’s Routing Table


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