Redistribution and Optimal path selection

Hi,

So, today I'm going to create lab showing how redistribution may effect the optimal path selection, first lets understand what does optimal path means?
Optimal means the one best route from A to B

Ok, so I'm using the following topology:

here you can see  ip address used and X is the router number

R5,R7,R4 are in EIGRP domain, and R3,R1,R2,R7,R4(interfaces) in OSPF domain.

 on R7,R4 we will do mutual redistribution in order to get the routes to R5
after doing the above this is what routing table of R5 looks like:

R5 routing table has two paths to all destinations in OSPF domain, coming from both gateways (75.0.0.7 and 45.0.0.4)

ok, so what to do in order to reach R3 loopback (3.3.3.3) using only one best route (optimal path)?

Ok, I will create a route map on both R4 and R7 that matches OSPF metric cost and if it is equal to (21) I will redistribute it with bandwidth (10000) else it will be redistribute with bandwidth (1000)

Ok lets configure it:

R7,R4

#route-map METRIC permit 10
#match metric 10 +- 11
# set metric 10000 10 255 10 1500
#route-map METRIC permit 20
#set metric 1000 10 255 10 1500

#router eigrp 100
#redistribute OSPF 1 route-map METRIC

Now checking R5 routing table to R3 loopback:

R5#show ip route 3.3.3.3
Routing entry for 3.3.3.3/32
  Known via "eigrp 100", distance 170, metric 284160, type external
  Redistributing via eigrp 100
  Last update from 45.0.0.4 on Ethernet0/1, 00:00:43 ago
  Routing Descriptor Blocks:
  * 45.0.0.4, from 45.0.0.4, 00:00:43 ago, via Ethernet0/1
      Route metric is 284160, traffic share count is 1
      Total delay is 1100 microseconds, minimum bandwidth is 10000 Kbit
      Reliability 255/255, minimum MTU 1500 bytes
      Loading 10/255, Hops 1
R5#

R5 now is using the best route which is via R4 as its only 21 cost to R3 loopback!

Thanks, I hope this was useful!

Good Luck!