IGRP (or EIGRP) or OSPF? best practices..

[mbellears2]

We currently have two locations(Site A and Site B), connected via fibre, both having BGP sessions with upstreams (Site A having two upstreams, Site B having one)

We have an aggregate advertisement of our entire /20 at Site A, and a more specific advertisement of 3 class C's at site B to ensure traffic destined for those particular class C's comes in via the Site B's upstream.

Currently the three upstreams are advertising def. routes to respective sites.

Static routes are in place on both sites routers i.e.

Site A has a static route for the three Class C's to Site B (Via the Fibre link)

Site B has a static route for the entire /20 to Site A (Via the Fibre link)

I am seeking suggestions/comments on best practices for our setup:

- Advertisement of our /20 network between the two sites - replacing the static routes with IGRP (or EIGRP) or OSPF?

- Advertise a default route from Site B to Site A (that has a lower precendence than routes already received from Site A's upstreams) - Will give us tertiary redundancy if both Site A's upstreams go down.

- Advertise a default route from Site A to Site B (that has a lower precendence than routes already received from Site B's upstream) - Will give us redundancy if Site B's upstream goes down.)

- Advertise our entire /20 out via Site B also, but give it a low priority compared to advertisement of /20 by Site A(Then if both Site A's Upstreams go down, the rest of the world can still get to our /20 via Site B) - BUT - still advertise the 3 class C's via Site B to ensure traffic destined for them comes in via Site B.

- Have a load-threshold in place on upstream links, that if exceeded, traffic would start going out via alternate upstream (Load balance?)

Thanks in advance,

Michael

[ruwhite]

It sounds like EIGRP or OSPF either would be fine for everything until you reach the last link, the load threshold link. You can't do that in any routing protocol at the moment, but you could with OER (Optimized Edge Routing). The only thing that's going to be touchy, perhaps, is preferring the local 0/0 over the 0/0 learned from the other site. You might have to set up a route map, or simply adjust the cost of the link between the two sites (using delay in EIGRP or cost in OSPF) to make certain the local default is always preferred.

:-)

Russ.W

[mbellears2]

Thanks for the reply - Which would you recommend (EIGRP or OSPF)? - With regards to flexibility/scalability/features?

Regards,

MB

[rajesh444]

If you are peering with 2 different ISPs BGP multi-homing could be an option as well.

The following links should be useful:

http://www.cisco.com/en/US/tech/tk365/tk80/technologies_configuration_example09186a00800945bf.shtml

http://www.cisco.com/en/US/tech/tk365/tk80/technologies_configuration_example09186a008009456d.shtml

[Craig Norborg]

I think both of them are fairly comprable in terms of features. I believe OSPF is a bit more flexible though and you can "control" its behavior a bit more, while EIGRP is a breeze to configure and very automatic to work.

I think the main issue with OSPF vs. EIGRP is compatibility though. EIGRP is definitely a "Cisco Only" protocol, and although it is very easy to configure and use, it is not compatible with anyone elses equipment.

As a matter of fact, its not even compatible with all "Cisco" equipment. One example would the the 3000 Series VPN concentrators which they purchased from Altiga I believe. Even though the products have been Cisco branded for quite awhile, they will only do OSPF routing, not EIGRP. I believe the same applies to other equipment that Cisco has that they purchased from other vendors also.

Although this might not be a huge factor if you're a 100% cisco shop, if your company might be thinking of acquiring other businesses and integrating their networks into yours, it definitely does complicate things quite a bit.