If a router running several IGP, such as two EIGRP processes, one OSPF:

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Will all the IGPs processes' acquired routes be stored in the router's one and only route table or more?

I mean, two questions:

  1. One logical router only have one route table, right?
  2. If that is right. how can the IGPs learned routes be isolated?

1 Answer 1

  1. Yes. One router have one forwarding table (FIB). It filled by routing protocols from their RIB. Often device can have different FIB's for different type of traffic (i.e. unicast and multicast).
  2. Each routing protocol have own routing table (RIB).

You can create isolated FIB by using VRF's (Cisco) or routing-instances (Juniper).

  • When the FIB filled by the routing protocols from their RIB, will there remove any routes? such as network repetition?
    – lustre
    Nov 13, 2018 at 13:51
  • Route selection (which is best and will get into FIB) is based on route selection algorithm of routing protocol (based on it's metrics) and then on administrative distances of each protocol. Nov 13, 2018 at 14:04
  • Little more here about metrics and AD. Nov 13, 2018 at 14:05
  • I do not understand the Often device can have different FIB's for different type of traffic, can you explain more? thank.
    – lustre
    Nov 15, 2018 at 10:37
  • @lustre, as I said in my answer, if you're using multicast routing on example, then probably you will have multicast FIB (MFIB) which is filling up with multicast routes. Nov 15, 2018 at 12:21

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