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TOPIC: EIGRP AS blending

EIGRP AS blending 15 years 4 months ago #2883

I know what Cisco says, but can someone tell me simply what are the steps and implications to sharing routes from two different EIGRP ASes.

Are there downsides, what if there is hostility between AS administrators?

How can you assure: 1. Complicity
2. Security
3. Reachability

What can you use to assure the other AS admin, that Sharing is "safe" and "easy" as well as less complicated than adding statics and NAT'g to homogenize networks.
A scapegoat is often as welcome as a solution...never memorize what you can look up.

Re: EIGRP AS blending 15 years 4 months ago #2963

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Your question is confusing at the very least. If anyone can help I would be curious to there response. As far as I know EIGRP is an Extended Internal Gateway Routing Protocol. It’s the Internal Routing Gateway Routing Protocol part that has me confused about your question. You do realize that the only External part of EIGRP is from other internal routing protocols? And, that is from the same autonomous system. So I have to ask what is you real question? I say this because while I know a lot of CCNA and CCNP I realize from reading a lot of these forums there is a lot more to networking than Cisco. So please enlighten me as to why two different autonomous systems would be sharing EIGRP routes?

Re: EIGRP AS blending 15 years 4 months ago #2985


One company, two different WAN providers, traffic from one WAN needs to be routed to the other WAN for different APPs that are hosted by the other WAN provider. The ASP doesn't want to add statics for every new node added to the "New" WAN so he (CCIE) suggested sharing routes between EIGRP ASes. (AS is what Cisco calls the EIGRP group number) not a true AS as IANA or ARIN knows it but similar in autonomy.

I have never heard of it and wanted to know if anyone else had.

I'm familiar with Enhanced Internal Gateway Protocol and the only way (I thought) to share routes between different ASes is to run BGP at the edges.

He disagrees and said we need to schedule time to talk about it. I may mention that the "new" WAN is divesting from his WAN because of unmet SLAs.
A scapegoat is often as welcome as a solution...never memorize what you can look up.

Re: EIGRP AS blending 15 years 4 months ago #3006

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This does not surprise me after all the times I've seen one CCIE's gospel disputed by another. I'm sure that part of it is because of the rapid advances in technology. After all in a very short time we now have a layer 3 switch (instead of advanced routing) and a blurring of the OSI layers to the extent that the new CCNA curriculum is completely restructured such that Cisco semester 1 (now CCNA 1) no longer emphasizes the OSI. Now it is just briefly mentioned and the TCP/IP is closer to center stage.

There are several Cisco books that very specifically state that IGRP and EIGRP use AS (autonomous system) numbers and go into detail how they can redistribute into each other automatically when using the same autonomous system numbers.

I am very interested in the results of a CCIE conference that promotes the use of EIGRP for a single AS with two “WAN providers" (by the way when you say WAN provider what exactly do you mean? I was assuming ISP). This would not be the first time I’ve seen contradiction to several established authors (CCIE authors) that insist on one thing just to have someone come along and say Opp’s now we have a better way.

However considering everything I have read concerning BGP and the extent I have seen it in use and the time and energy several CCIE authors have put into emphasizing it as the internet protocol please don’t blame me for being skeptical. :roll:

By the way just in case I have misunderstood your topology (I've re-read it a few times). I will say this: If what your are saying is that One company has three different locations (LANs) that are being connected together by two WANs in a hub and spoke topology then EIGRP would be very appropriate provided all routers are Cisco routers. This one company would be by definition a single autonomous system even if they have not been assigned an AS number.

Re: EIGRP AS blending 15 years 3 months ago #3051

Topographics: Hub (Corporate office) and spoke design with frame WAN links, 70 or so, to remote hospitals (both Acute Care-AC and Behavioral Health-BH), with 2 PVCs aggregating back to 2 different locations; Corporate HQ and a Third Party ASP who manages the edges and provides critical pharma, HR and document imaging apps to the hospitals. Due to the nature of the BH sites, ASP doesn't serve anything but HR hence, doesn't treat the sites as critically as the AC sites during downtime or routing issues. I might also add that the HR app is most recent and the BHs only have PVC terminating back to Corp HQ.

Due to the lack of SLA satisfaction, I am migrating the BH sites (40 or so) to a new WAN provider, same topographics, whereas I manage the edges.

ASP has one EIGRP group# (AS as Cisco terms it) and doesn't want the BH sites to paticipate.

LAN group at HQ doesn't want our core to participate in either EIGRP group (ingnorant of the fact that it would make their life simpler.)

Now, for each site I bring up on new WAN (with different EIGRP group#) both our core and ASP hub need statics.

Our core group often inaccessible, ASP slow in the process (often 5 business days) and me turning up sites often @2 or 3AM on weekends (after has posed a routing issue.

ASP, tired of me screaming at them that the BH sites can't access BH app, even after statics are added to our core (until they came to their senses and after much persuasion about needing statics on their hub for my new WAN) are talking sharing routes between EIGRP ASes.

Hence, my original question. I would like to dictate what they do to solve this rather than waiting for them to drag their feet (remember, I'm also hitting their bottom line) and come up with a solution other than me screaming at them to add statics on a break/fix basis.

As for AS#s, as the world knows them on the internet, we have one ASSIGNED by ARIN so as to run BGP at our edge to the public via multiple ISPs. So you see, neither ARIN nor the public, know anything of the EIGRP group#s(ASes) which are CHOSEN not ASSIGNED and can be the same number on millions of private WANs inconsequentially. Wheras on the public net, each and every AS needs to be uniquely assigned (with a cost associated) by a global governing body such as ARIN on the western part of the northern hemisphere.

So now that we're both on the same page as far as EIGRP group#s (which in Cisco's docs about EIGRP Cisco likens them to AS numbers for disparate networks and goes on further to call them AS#s "in the interest clarification?") and

any suggestions?
A scapegoat is often as welcome as a solution...never memorize what you can look up.

Re: EIGRP AS blending 15 years 3 months ago #3053

10 re-read post
20 scratch head
30 goto 10

Sahir Hidayatullah. Staff - Associate Editor & Security Advisor
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