Configuration Guide Vol. 3


13.4.4 Negotiation of support functions

Capability negotiation is a means of negotiating which capabilities are supported by the peers. This is done by adding capability information to the OPEN message at the establishment of a BGP4 negotiation session. Functionality that is matched (supported) by the respective peers' advertised capability information can be used by those peers.

In the Switch, the following capability information can be added to the OPEN message: IPv4 unicast routing, route refresh capability (Capability Code:2), route refresh capability (Capability Code:128), and the graceful restart functionality (Capability Code: 64). When an OPEN message without any capability information is received from a peer, only IPv4 unicast route advertisements will be sent over the established BGP4 connection.

The following table describes the capabilities that can be negotiated.

Table 13-9: Features that can be negotiated

Capability

Capability information in OPEN message

Description

IPv4 routing

Capability Code: 1

AFI field of the Capability Value: 1

SAFI field of the Capability Value: 1

IPv4 unicast routes can be sent and received between the peers.

Route refresh capability

Capability Code : 2

AFI of Capability Value: 1 #

Route refresh is supported on IPv4 routes.

Capability Code : 128

AFI of Capability Value: 1 #

Graceful restart

Capability Code : 64

AFI field of the Capability Value: 1

SAFI field of the Capability Value: 1

Use graceful restart.

#: Route refresh is supported if negotiation of either of these two capabilities is successful.

The following figure illustrates how negotiation operates.

Figure 13-18: Concept of negotiation behavior

[Figure Data]