EIGRP Configuration Help

Hello All,

I have a network, rather large which is at present utilising static routes, and they are mow moving to EIGRP. The main problem is that within the core Routers (3 of them in 3 different geographical locations) the IP addressing scheme isn't contingent. I'm worried with EIGRP that the route tables will get unduly large.

Below is an example of the network topology

10.1.0.0/16 10.11.0.0/16 10.200.0.0/16 --------R1--10.254.254.1/30---R2------10.254.254.5/30---R3----- 10.66.0.0/16 10.157.0.0/16

This is a subset of the network - basically all locations (approx 20 in all) each have allocated a 10.x.0.0/16 subnet R2 is the central router, and at present the EIGRP commands are as follows:-

Router EIGRP 10 network 10.0.0.0 no auto-summary

First querstion - is it possible to use multiple EIGRP summary commands.

Second question - where links have a /30 network each side as in the example above, and if I were to change EIGRP to explicit network statements for each subnet behind each router, what routrs need to know about the serial link's /30 network. For example,taking R1

Router EIGRP 10 network 10.1.0.0 0.0.255.255 network 10.200.0.0 0.0.255.255

Do I also need to add to this NETwork 10.254.254.0 0.0.0.255

Does also a similar scenario hold true for R3

How would one configure EIGRP for a network such as above to ensure its stability. Unfortunately readdressing the whole network to ensure continguous IP addressing is not an option at present.

Many thanks in advance for any help or info.

Gerard Gallagher

Reply to
Gerard Gallagher
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Just as some comments about general good design, I would only have network statements for the networks where you are actually exchanging routes. I would then put summary addresses on the routing vlans outbound from the core router that actually owns the networks. You can do this via going on the vlan and doing a ip summary-address eigrp a.b.c.d . I would also make sure that you use passive-interfaces as the default, and only allow routing on one or two vlans (two is better if you have redundant wan hardware to minimize reconvergence, especially if you make l2/l3 home on one core, and other network homed on the other core).

Where possible, use summary addresses (probably manual), limit peers/ neighbors with passive interfaces, and you may want to consider leaving the statics in and verifying eigrp table before yanking them. If you have remote sites, I would use the trick of doing a save on the config, do 'reload 20' or something like that to reload the router in

20 minutes, so if you lose connectivity, itll bounce and come back to its startup-config in case you lock yourself out via routing.

Just my 2 cents.

Reply to
Trendkill

If you have remote routers that are single-homed then implement EIGRP stub routing on each of these routers.

see

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An EIGRP stub router is not queried about routes that it could not know anything about.

The control of EIGRP query boundary is fairly important in EIGRP network design.

How many routers in total ?

How many IP subnets in total ?

Reply to
Merv

Thank you for your comments - and they are all correct.

In relation to the core I do have "passive-interface VLANx" on all except 2 VLANS

In one location I have a 10.202.0.0/16 network, but this is VLAN'd down to

10.202.x.x/24. Under EIGRP I have passive interfave VLANx configured. Is this what you are referring to?

Again - appreciate your comments, all greatfully accepted!

Reply to
Gerard Gallagher

Merv, Yes, all single-homed locations are configured as stub.

Total routers in the region of 40-50 Subnets again much similar. The network design is archaic and a relic of the past in terms of subnets, as each location was allocated a 10.x.0.0/16 subnet. This would not be too bad, but there are basically 3 core locations however the spoked sites off these locations are not continguous in terms of IP subnets so cannot summarise all that easily.

Example - one core location has 10.11.x.x/16, and spoked from this are

10.25,10.50,10.133, /16

Hope this makes sense and thanks

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Reply to
Gerard Gallagher

Most routers can handle pretty large routing tables, so long as you summarize down to /16s (presuming you dont have /24s outside of a single geographical area), that should be fine. Truthfully, even if you had all /24s, it shouldnt be that bad unless this is a retail network and you have 1000s of networks. At this point, I would try to summarize to /16s, or /17s-20s if /16s are too broad, and you should be fine. I wouldn't go crazy, as any decent router should handle a good amount of routes.

Reply to
Trendkill

If you have 3 core and most of the other routers are stubs, then I do not think that I would spend time with summaries until the network is re-addressed.

I would spent time looking at any network instability (i.e link flaps, etc) as these are hard on any routing protocol.

Watch for any SIA events. Look at the output of sh ip eigrp nei to see how stable adjacencies are, etc, etc.

Reply to
Merv

You shouldn't have any issues at all, 40 or 50 routers is a small network, not a large one. If you had 400 or 500 then you have a large network. You don't need too worry too much about summary-routes or stubs right away. Get it working first and start tweaking with summary-routes and stubs. Once you get it implemented and familiar with troubleshooting EIGRP issues and getting more comfortable with it, then start doing thing to optimize your network. You can only summarize efficiently if you have a very well thought out IP addressing scheme and it sounds like you do. The biggest issue with EIGRP is having full routing tables on low-end routers like 2600 or lower and you have link failures that make large numbers of routes go away.

3600's can be an issue as well if you have more than 500 or 600 routes. The low end routers can't keep up with all the routing updates and EIGRP queries and neighbors start resetting, which causes more updates and queries. The low end routers should not be in the core, and should only be getting default summaries or have distribute lists on them to limit what routes get installed in the routing table. Good Luck!

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Reply to
Thrill5

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