H3C S7500 Series Ethernet Switches Operation Manual

Operation Manual – Routing Protocol
H3C S7500 Series Ethernet Switches Chapter 6 BGP Configuration
6-3
Route-refresh packets. Among these types of BGP packets, the first four are
defined in RFC 1771, and the rest one is defined in RFC 2918.
II. Open
Open massage is used to establish connections between BGP speakers. It is sent
when a TCP connection is just established.
Figure 6-2 shows the format of an Open
message.
15
BGP Identifier
31
Version
My Autonomous System
Hold Time
Opt Parm Len
Optional Parameters
70
Figure 6-2 BGP Open message format
The fields are described as follows.
z Version: BGP version. As for BGP-4, its value is 4.
z My Autonomous System: Local AS number. By comparing this filed of both sides,
a router can determine whether the connection between itself and the BGP peer
is of EBGP or IBGP.
z Hold time: Hold time is to be determined when two BGP speakers negotiate for
the connection between them. The Hold times of two BGP peers are the same. A
BGP speaker considers the connection between itself and its BGP peer to be
terminated if it receives no Keepalive or Update message from its BGP peer
during the hold time.
z BGP Identifier: The IP address of a BGP router.
z Opt Parm Len: The length of the optional parameters. A value of 0 indicates no
optional parameter is used.
z Optional Parameters: Optional parameters used for BGP authentication or
multi-protocol extensions.
III. Update
Update message is used to exchange routing information among BGP peers. It can
propagate a reachable route or withdraw multiple pieces of unreachable routes.
Figure 6-3 shows the format of an Update message.