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9.3 | ![]() |
Configuring BGP | |
9.3.6 | ![]() |
Peering |
Any two routers that have formed a TCP connection in order to exchange
BGP routing information are called peers or neighbors.
Figure It is important to remember that the BGP peers will never become established unless there is IP connectivity between the two peers. In this example, OSPF is used to establish the required internal connectivity between RTD and RTE.
In the configuration from RTF, the ebgp-multihop 2 command is seen being used as part of the neighbor configuration. This is an indication that the exterior BGP peer is not directly connected and can be reached at a maximum of two hops away. Remember that EBGP multihop is applicable only with EBGP, and not with IBGP.The example also shows how the peer connection will look after the neighbors are in an established state. RTF sees neighbor 172.16.2.254 as an internal neighbor that belongs to AS3. The neighbor connection is running BGP Version 4 with a table version of two (2). The table version changes every time the BGP table is updated. The other RTF neighbor, 192.68.12.1, is also in an Established state. This is an external neighbor that belongs to AS2. Notice that the display indicates that this neighbor is two hops away and is configured using the ebgp-multihop command.
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