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Redistribute OSPFv2 with EIGRPv3

Azlord_Cisco
Beginner
Beginner

Hi there

 

I need some help with a company merger type scenario.

 

I have two sites: A and B. Site A runs OSPFv2 while site B runs EIGRPv6. 

 

The topology of the main routers is quite basic:

 

Site A R1 <---> Site B R1.

 

Both of the main routers are 1841 models and dual stacked for basic connectivity.

 

I need to redistribute routes between these two routers so that branch routers connected to them can obtain routes of the other sites using only their respective routing protocol. There is the option of using a L3 switch between the two main routers, but would like to attempt with just the two main routers first.

 

After some sample router configurations for this scenario.

 

 

1 Accepted Solution

Accepted Solutions

I believe that dual stack is the way to go. The fundamental problem with trying to redistribute is that the addresses are completely incompatible. Redistribution works in IPv4 networks because while the protocols differ in the metrics that they use they are both using the same kind of addressing. A 32 bit address coming out of EIGRP is easily understood by OSPF. But think about what would happen if your EIGRPv3 tries to redistribute a 128 bit address to OSPF?

 

HTH

 

Rick

HTH

Rick

View solution in original post

4 Replies 4

Richard Burts
Hall of Fame
Hall of Fame

As I read your post the first time I was thinking - ok redistribution between two protocols and how to accomplish that (which is not so difficult). And as I read it a couple more times I realized that there are much bigger and more challenging issues here. The most significant thing is that one site is running IPv4 while the other is running IPv6. So on the site currently running IPv4 you are going to have to add processing capability for IPv6. And on the site currently running IPv6 you are going to have to add processing capability for IPv4.

 

I assume that both sites have default routes in place that draw all traffic for unknown destination addresses to their R1. So in terms of exchanging routing information you only need to know specific destination subnets on the R1s. But every router in site A is going to need to be configured so that if it receives an IPv6 packet that it will forward it to R1. And every router in site B is going to need to be configured so that if it receives an IPv4 packet that it will forward it to R1.

 

HTH

 

Rick

HTH

Rick

hi Rick.

 

Yes, you are correct. Site A runs IPv4 with OSPFv2 and Site B runs IPv6 with EIGRPv6. It's a company merger type scenario challenge where each site runs a different protocol version.

 

As far as using Cisco models for the environment, it would seem that only the higher-end Cisco devices can perform NAT-64 translation. So I am leaning towards dual-stacking both sites as I am limited to 1841 router and 3750 switch models. Running a Linux-based NAT64 box is out of scope.  

 

I suppose I could run OSPFv2 and EIGRPv6 simultaneously on both sites without a need for redistribution if I am dual stacking, but is there still a method for each site to run it's own routing protocol and redistribute them with a 3750 switch or 1841 model router in between?

 

Below is the sample topology

 

 sample topology.JPG

I believe that dual stack is the way to go. The fundamental problem with trying to redistribute is that the addresses are completely incompatible. Redistribution works in IPv4 networks because while the protocols differ in the metrics that they use they are both using the same kind of addressing. A 32 bit address coming out of EIGRP is easily understood by OSPF. But think about what would happen if your EIGRPv3 tries to redistribute a 128 bit address to OSPF?

 

HTH

 

Rick

HTH

Rick

I am glad that you find my response to be helpful. Thank you for marking this question as solved. This will help other participants in the forum to identify discussions that have helpful information. These forums are excellent places to ask questions and to learn about networking. I hope to see you continue to be active in the forum.

 

HTH

 

Rick

HTH

Rick
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