EBGP Peer Relationships

E-BGP peer relationships are, undoubtedly, the most common type of BGP peering relationship that most enterprise network professionals will encounter. Regardless of how many peers one BGP speaker has, only a few types of connections can occur between E-BGP peers.

• Directly connected peers— Peers that are directly connected; usually over a WAN connection between the customer and the service providers, or between transit peers.

• IndirecEly connected peers— N-BGP peers that must cross one or more non-BGP-speaking routers to reach each other.

Configuring direct E-BGP connections is an extremely straightforward process involving only three steps .

Step 1. Enable BGP routing using the router bgpas-number command.

Step 2. Configure BGP peers using the neighbor ip-add ressremote-asrem ote-as-number command. E-BGP peer relationships are formed if the AS number entered during the configuration of the neighbor command is not the same as locally configured AS number.

Step 3. (Optional) Specify the networks that the local peer is to advertise using the networknetwork [ masksubnet-mask ] command. Similar to the EIGRP network command, tlue BGP network co mmand specifies networks that the local peer wiN advertise; ¡1° whose networks do not fall exactly between the classful boundaries, the subnet masks define those networks.

Figure 8-8 shows an example of the direct E-BGP configuration between the Sideshow and Crusty routers.

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