ip bgp

To enable 4-byte ASN support in BGP speaker, configure the BGP speaker's policy for handling the overlapping routes, and enable synchronization between BGP and IGP, use the command ip bgp in Global Configuration Mode. The no form of the command disables 4-byte ASN support in BGP, resets Overlap route policy to its default values, and disables the synchronization between BGP and IGP.

ip bgp

ip bgp

{ {four-byte-asn } { | overlap-policy } { {more-specific } { | less-specific } { | less-specific } { |both} } { |synchronization} }

no ip bgp

no ip bgp { {four-byte-asn } { | overlap-policy } { |synchronization} }

Parameters

Parameter	Type	Description
`four-byte-as`		Enter to enable 4-byte ASN support in BGP speaker. Note: This command executes only when BGP Speaker Global Admin status is shut down in the system.
`overlap-policy`		Enter to configure the configure the BGP speaker's policy for handling the overlapping routes. Note: This command executes only if BGP Speaker Local AS number is configured and BGP Administrative status is down.
`more-specific`		Enter to configure the overlap policy for BGP speaker as more-specific. This implies that when an overlapping route is received, more-specific routes are installed in the RIB tree.
`less-specific`		Enter to configure the overlap policy for BGP speaker as less-specific. This implies that when an overlapping route is received, less-specific routes are installed in the RIB tree.
`both`		Enter to configure the overlap policy for BGP speaker as both. This implies that when an overlapping route is received, both the more-specific and less-specific routes are installed in the RIB tree. This is default.
`synchronization`		Enter to enable synchronization between BGP and IGP. BGP speaker does not advertise a route to an external neighbor unless that route is local or exists in the IGP. This command allows routers and access servers within an autonomous system to have the route before BGP makes it available to other autonomous systems. Note: This command executes only if BGP Speaker local AS number is configured.

Mode

Global Configuration Mode

Default

4-byte ASN support —enabled

overlap-policy—both

Synchronization between BGP and IGP is disabled

Examples

iS5comm(config)# ip bgp four-byte-asn

iS5comm(config)# ip bgp overlap-policy more-specific

iS5comm(config)# ip bgp synchronization