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| 9.3 |  | Configuring BGP |
| 9.3.2 |  | EBGP and IBGP |

When configuring BGP, remember that BGP supports the following two types of sessions, each with slightly different configuration requirements:

- EBGP session – Occurs between routers in two different autonomous systems. These routers are usually adjacent to one another, sharing the same medium and a subnet. See RTA in Figure .
- IBGP session – Occurs between routers in the same AS, and is used to coordinate and synchronize routing policy within the AS. Neighbors may be located anywhere in the AS, even several hops away from one another. An IBGP session typically occurs between routers in the same AS in an ISP.

If the

AS-number configured in the router bgp command is identical to the AS-number configured in the neighbor statement, BGP will initiate an internal session. If the field values are different, BGP will build an external session.