OSPF & EIGRP redistribution

[samsam_wang]

3 routers, R1(s0,e0), R2(s0,e0,s1,e1),R3(s1,e1)

R1 s0------R2 s0 (run OSPF)

R1 e0------R2 e0 (run EIGRP)

R3 s1------R2 s1 (run OSPF)

R3 e1------R2 e1 (run EIGRP)

there are some other routers connect to R1 and R3, run OSPF or EIGRP between them, we don't care those.

Now, I don't know where I should redistribute EIGRP and OSPF. every time when I try to redistribute them on R1 or R2 or R3, there is a loop there.

who would like give me some advice?

thanks

[ruwhite]

Any time you redistribute between two dynamic routing protocols in more than one place, you have the possibility of forming loops in the network. There are a couple of solutions:

-- Filter route based so they cannot be reinjected back into the protocol they came from at the redistribution point. This would normally be done so routes redistributed from OSPF into EIGRP are filtered from being redistributed back into OSPF at every redistribution point.

-- Use tags in EIGRP and OSPF to tag routes being redistributed out, and then blocking those routes from being redistributed at the other redistribution routers.

These links might help:

http://www.cisco.com/en/US/tech/tk365/tk207/technologies_tech_note09186a008009487e.shtml

http://www.cisco.com/en/US/products/sw/iosswrel/ps1829/products_feature_guide09186a008012db77.html

:-)

Russ.W

[samsam_wang]

thanks a lot.

I just want to know which point is the best, in fact, my topology is more complex then this(R1,R2,R3). I try to filter some routes, but the loop is still there. so i will try the tag route. thanks

meanwhile, for single point redistribution, it is still possible form loop. but I got information from cisco.com no problem for the single point, it is right?

thanks

[ruwhite]

A single point of redistribution should not land you in a loop. At least I don't know of any way to form a loop with a single point of redistribution.

:-)

Russ.W

[samsam_wang]

two questions

first one, single point redistribtion loop example.

R1 s0-----s0 R2 run IGRP

R1 e0------run RIP

when redistribute IGRP and RIP, there is a loop.

I do have an example between RIP and EIGRP

second question,

my topology of redistribution ospf and eigrp

R1 s0------s0 R2 (OSPF)

R1 e0------e0 R2 (EIGRP)

R2 s1--FR--s0 R4 (OSPF)

R4 s1------s1 R5 (OSPF)

R5 e1------e1 R2 (EIGRP)

so where I should redistribute them?

I want to ask one more question about EIGRP load balancing.

R1 s0---64k----s0 R2 (metric=10000)

R1 e0---10M----e0 R2 (metric=2)

R1 s1--1.544M--s1 R2 (metric=5000)

run eigrp between them.

for "variance" under eigrp, it doesn't work for the ethernet link.(only 1 to 128) . but I got my formulation to let three metric equal just add some "delay" on ethernet and T1 links.

after I add "delay", if the three metric exactly equal, that means "load balancing"? thanks

thanks a lot

[ruwhite]

I don't know of any way to form a loop with a single point of redistribution--the router can only prefer one of the two routes available.

As for where to redistribute, it's hard for me to understand your network diagram. I would pick the one with the highest bandwidth link, or I would use the tags, as outlined on the tech note on Cisco Online, to redistribute in multiple places.

Russ.W