Company ABC closes a deal with a Partner Company that requires redundant network paths between the two networks. This requirement is met by enabling 2 connections: one FastEthernet between R1 and R5 and one Serial link between R2 and R6.

Static routes are configured on R1 and R2 for the 2 subnets in partner's network (172.16.10.0/24 and 172.16.11.0/24) and they are redistributed into the OSPF Area 0:


quiz-12

Unfortunately, the network administrator is not happy with the OSPF best path performed on the company router R3 for those external routes.
As displayed above, R3 prefers the path via R4 -> then R2 -> then Serial link to reach the Partner's network. 

R3#traceroute 172.16.10.5
...
  1 10.0.34.4 80 msec 48 msec 28 msec
  2 10.0.24.2 64 msec 40 msec 68 msec
  3 192.168.2.6 32 msec 56 msec 64 msec
  4 172.16.10.5 124 msec *  148 msec
R3#
R3#sh ip route 172.16.10.0
Routing entry for 172.16.10.0/24
  Known via "ospf 1", distance 110, metric 20, type extern 2, forward metric 2
  Last update from 10.0.34.4 on FastEthernet0/1, 00:06:56 ago
  Routing Descriptor Blocks:
  * 10.0.34.4, from 192.168.2.2, 00:06:56 ago, via FastEthernet0/1
      Route metric is 20, traffic share count is 1
R3#

Why is it so? Is there a problem with OSPF or the selected path is really the shortest/correct one ?

Notes:
- there was no manipulation of OSPF costs !!
- don't worry about return traffic: static routing for network 10.0.0.0/8 was configured on Partner devices !

Post your solution in the 'Comments' section below and subscribe to this blog to get the solution and more interesting quizzes.