Re: IEExpert Vol 2 version 4.1 task 4.11

Hi Abdul Jaleel,

I think I remember this one. It is required to prevent a loop. If a
rip route is advertised into OSPF, it can later be redistributed into
eigrp, before being redistributed back into OSPF. If that happens then
SW1 will receive the route back with a OSPF AD. It would then prefer
that over the RIP route which was the original source.

This can happen despite EIGRP external routes having a higher AD than
OSPF, an example would be if the OSPF interface on R4 failed. R4 would
still learn the route via EIGRP and, since it also has an OSPF loopback,
it would still insert it into OSPF. When full connectivity was
restored, you would then have SW1 and R4, both with the same external
OSPF route. So you need to make sure that SW1 does not use the external
route it learns from R4, over the locally redistributed one it creates.

Paul.

 
kaniyath minha wrote:
> Dear
>
> While redistributing RIP into OSPF and vise versa on Rack1SW1, why the
> distance 109 command is used under router rip command.
>
> There is no explanation on SG and question is not specifying anything for
> changing this.
>
>
> Below shows the question and answer which is showed in SG
> *
> Question *
>
> 4.11. IGP Redistribution
>  Redistribute between RIP and OSPF on SW1.
>  Redistribute between OSPF and EIGRP on R2, R3, and R4.
>  Ensure that full reachability is maintained throughout the IGP domain
> when the Frame Relay circuit between R3 and R5 is down.
>
> *Answer in SG*
>
> Task 4.11
> SW1:
> router ospf 1
> redistribute rip subnets
> network 132.1.17.7 0.0.0.0 area 17
> !
> router rip
> redistribute ospf 1 metric 1
> distance 109 *(Why this command required in this particular scenario)
>
> *Thanks and Regards*
> *Abdul Jaleel Kaniyath*
> *
>
>
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Received on Wed May 06 2009 - 12:44:31 ART