Should I be worried about EIGRP SIA, with a full Mesh topology?

lon21lon21 Member Posts: 201
Dear All,

I'm trying to design a network but our company which is planning to have between 5-6 sites. All sites have backup links which is via a 2Mbps MPLS, 2Mpbs point to point links and main 100Mpbs point to point links.

The plan is to run EIGRP one AS over these sites. Two of the site will house about 30 users and the other sites about 5.

I would like a full mesh topology where each site can reach each other site even if it has to go via another site(s). Each site will have one local router which will terminate its local connection and the main and backup link.

After some research I have been informed that EIGRP can bring a network down based on its Query messages as routers lose routes.

My concern is that I'm not able to use summary address or Stubs as these site could be used to connect to other sites. I'm sure these is something which is common in todays networks.

Is this something which I should be worried about?

Any advise would be appreciated?



  • JackaceJackace Member Posts: 335
    Why would you not be able to use summary routes?

    One of the benefits of summary routes in EIGRP is:

    "Reduces Query scope: EIGRP Query stops at a router that has a summary route that
    includes the subnet listed in the Query but not the specific route listed in the Query."
  • unclericounclerico Member Posts: 237
    If you could provide your prospective network topology in an image that would help. As for SIA and the whole query process, remember that your routes only go active if you don't have feasible successor(s) available. Also, if you are re/designing this from the ground up you have the opportunity to be able to use hierarchical addressing to make for easy summarization. As for stubs, yes, if you are wanting to use these sites for transit to other sites in case of failures then no stub for you. Again, post a schema so we can see. One last thing, any particular reason you chose EIGRP? Just curious...
    Preparing for CCIE Written
  • lon21lon21 Member Posts: 201
    As each site would be a transit site to reach other sites, the summary routes would all be the same. The summary address itself would be the same for each site. Unless I'm incorrect, my understanding of the summary address is that it informs its neighbours that these are the networks I can reach, as the network is a full mesh each site can reach each site.

    The choice was EIGRP as we have Cisco routers at all sites, easy to configure and fast convergence . Would you recommands using OSPF, any reason why?

    I'll draw a diagram this evening.

  • NetworkVeteranNetworkVeteran Member Posts: 2,338 ■■■■■■■■□□
    lon21 wrote: »
    The choice was EIGRP as we have Cisco routers at all sites, easy to configure and fast convergence . Would you recommands using OSPF, any reason why?
    A common reason folks recommend OSPF over EIGRP is because it doesn't tie you down to a single vendor. You could easily deploy, for example, a Juniper router at a later time. A similar no-summary OSPF configuration can be as simple as typing "ip ospf 1 area 0", and its convergence time is plenty good enough for many ISPs and large enterprises.

    Note: I'm not making a recommendation as I don't know you nor your network well.

    I have a friend who only deploys EIGRP. In his case it makes great sense--he builds and support many networks, and to simplify that he's chosen to always go with one vendor and one routing protocol. He began with IGRP, so EIGRP was the simplest path.
  • unclericounclerico Member Posts: 237
    The possibility of using summaries still exists; it all just depends on how things are laid out. When I get a chance I'll draw something up. Hopefully you can get to your schema and post it so I can use it as a baseline.
    Preparing for CCIE Written
  • lon21lon21 Member Posts: 201

    Extremely sorry, not had much time therefore I done a quick draw on the sites and its links. The 100Mb & 2Mb are L2 links and MPLS is L3 (managed).

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