Mp-Bgp - H3C S9500E Series Configuration Manual

stale. However, during the configured GR Time, it still uses these routes for packet
forwarding.
After the restart, the GR Restarter will reestablish a GR session with its peer and send a new
4.
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 with 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, such as IPv6.
To support more network layer protocols, IETF extended BGP-4 by introducing 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 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 the following 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 previous two path attributes are both optional non-transitive, so BGP speakers not supporting
multiprotocol ignore these 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,
see RFC 1700 (Assigned Numbers), including VPN extension and IPv6 extension. Different
extensions are configured in respective address family view.
For information about the IPv6 extension application, see IPv6 BGP in the Layer 3 – IP Routing
•
Configuration Guide.
This chapter provides no detailed commands related to any specific extension application in MP-BGP
•
address family view.
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