Mp-Bgp; Protocols And Standards - H3C LS-3100-52P-OVS-H3 Operation Manual

4) After the restart is completed, the GR Restarter will reestablish GR sessions with its peers and
send a new GR message notifying the completion of restart. Routing information is exchanged
between them for the GR Restarter to create a new routing table and forwarding table and have
stale routing information removed. Then the BGP routing convergence is complete.

MP-BGP

Overview
BGP-4 supports IPv4 unicasts, but does not support other network layer protocols like IPv6.
To support more network layer protocols, IETF extended BGP-4 by introducing Multiprotocol
Extensions for BGP-4 (MP-BGP) in RFC 4760.
Routers supporting MP-BGP can communicate with routers not supporting MP-BGP.
MP-BGP extended attributes
In BGP-4, the three types of attributes for IPv4 address format, namely NLRI, NEXT_HOP and
AGGREGATOR (AGGREGATOR contains the IP address of the speaker generating the summary route)
are all carried in updates.
To support multiple network layer protocols, BGP-4 puts information about network layer into NLRI and
NEXT_HOP. MP-BGP introduced two path attributes:
MP_REACH_NLRI: Multiprotocol Reachable NLRI, for advertising feasible routes and next hops
MP_UNREACH_NLRI: Multiprotocol Unreachable NLRI, for withdrawing unfeasible routes
The above two attributes are both optional non-transitive, so BGP speakers not supporting
multi-protocol ignore the two attributes and do not forward them to its peers.
Address family
MP-BGP uses address families to differentiate network layer protocols. For address family values, refer
to RFC 1700 (Assigned Numbers). Currently, the system supports multiple MP-BGP extensions,
including VPN extension and IPv6 extension. Different extensions are configured in respective address
family view.
For information about the VPN extension application, refer to MCE Configuration in the IP Routing
Volume.
For information about the IPv6 extension application, refer to IPv6 BGP Configuration in the IP
Routing Volume.
This chapter gives no detailed commands related to any specific extension application in MP-BGP
address family view.

Protocols and Standards

RFC1771: A Border Gateway Protocol 4 (BGP-4)
RFC2858: Multiprotocol Extensions for BGP-4
RFC3392: Capabilities Advertisement with BGP-4
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