Task 5.1 - Why do we need to redistribute BGP into IGP

I did this Mock Lab recently but when I got back my report, I missed this task because the proctor said "BGP prefixes are not redistributed into IGP"

I really don't know why we need to do this.

Basically we're running BGP on R1, R4 and R6 and all of them are AS 100 with R1 configured as Route-Reflector to both R4 & R6.

R4 has an eBGP peering with BB3 and R6 has an eBGP peering with BB1. Both BB1 & BB3 are both in AS 54. All routers has reachability to the prefixes from AS54, so why do we need to redistribute BGP into IGP.

Whoever has done this lab in the past or experts from IE should be kind enough to comment on this task !




  • I haven't done ML #4, but if prefixes attached to non-BGP routers are advertised into BGP, those non-BGP routers will need to be able to reach BGP prefixes when traffic originated from the backbone routers or from the networks behind the backbone routers is sent to the advertised networks.

    To ensure reachability from BGP routes to the advertised network and back, careful redistribution of BGP prefixes into IGP may be necessary.

  • Hi Olu


    I did the same thing - looking back at the begining it states..

    upon completion, all devices should have full reachability to all networks in the routing domain, including any network generated by the backbone routers unless explicitly specified.


    cost me a few other points also.




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