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Configuring BGP Confederations (Optional)

To help solve BGP scaling problems caused by the IBGP full-mesh requirement, you can divide your AS into sub-ASs called confederations. As Figure 73 shows, the connections between the sub-ASs are made through EBGP sessions, and the internal connections are made through standard IBGP sessions.

In the sample network, AS 17 has two separate confederations (sub-AS 64512 and sub-AS 64513), each of which has multiple routers. Within a sub-AS, an IGP (OSPF, for example) is used to establish network connectivity with internal peers. Between sub-ASs, an external BGP peering session is established.

Figure 73: Typical Network Using BGP Confederations

Image g015035.gif

To configure the BGP confederations shown in Figure 73:

Navigate to the top of the configuration hierarchy in either the J-Web or CLI configuration editor.
Perform the configuration tasks described in Table 92.
If you are finished configuring the router, commit the configuration.
To check the configuration, see Verifying a BGP Configuration.

Table 92: Configuring BGP Confederations

Task	J-Web Configuration Editor	CLI Configuration Editor
Navigate to the Routing-options level in the configuration hierarchy.	In the configuration editor hierarchy, select Routing-options.	From the top of the configuration hierarchy, enter edit routing-options
Set the AS number to the sub-AS number 64512. The sub-AS number is a unique AS number that is usually taken from the pool of private AS numbers—64512 through 65535.	In the AS Number box, enter the sub-AS number. Click OK.	Set the sub-AS number: set autonomous-system 64512
Navigate to the Confederation level in the configuration hierarchy.	In the configuration editor hierarchy, select Routing-options>Confederation.	From the top of the configuration hierarchy, enter edit routing-options confederation
Set the confederation number to the AS number 17.	In the Confederation as box, enter 17.	Set the confederation AS number: set 17
Add the sub-ASs as members of the confederation. Every sub-AS within the AS must be added as a confederation member.	Next to Members, click Add new entry. In the Value box, enter the sub-ASs that are members of this confederation. Separate multiple sub-ASs with a space.	Add members to the confederation: set 17 members 64512 64513
Using EBGP, configure the peering session between the confederations (from Router A to Router B in this example). When setting the peer AS number for these sessions, use the sub-AS number rather than the AS number.	See Configuring a Point-to-Point Peering Session (Required).
Using IBGP, configure internal sessions within a sub-AS. You can configure an IBGP full mesh, or you can configure a route reflector.	To configure an IBGP full mesh, see Configuring BGP Within a Network (Required). To configure a route reflector, see Configuring a Route Reflector (Optional).

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