4.9 - Redistribution, Chicken and Egg Eroblem With The Provided Solution

Doesn't look right to me when it comes to changing OSPF's external AD from 110 to 171.


This will lead to a chicken and egg problem. If OSPF externals gets better than EIGRP external routes, when routers redistributed by R6 will have trouble in the EIGRP domain. And if EIGRP EX routes get better than OSPF external routes, then R5 redistributed routes will have trouble in the OSPF domain.

Basically, changing this AD for ALL externals or ALL internals shouldn't happen in my view.. If we want to do it right,  then we should selectivly change AD based on an ACL that matches exactly the redistributed routes accordingly.


Your feedback please.


  • I agree, a bit over the top.

    How I tackled this was that I selected all EIGRP 170 routes before enabling any redistribution and increased AD for them under OSPF to 171 on R2, R3 and R4. All OSPF originated (including RIP routes from SW1) stayed within OSPF as more preferable. I had full reachability from R6 and R5, all routes in routing tables on R2, R3 and R4 were stable as far as I tell looking at times of how long routes have been in the routing tables.

    I used TCL script to check connectivity and it was all ok. I did some more investigating and couldn't find any fault although looking at others' posts I can't believe it would be so straight forward. I'll probably get back to this the other day and double check it all again.

    The only issue was that multicast testing didn't work straight away.



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