Mp-Bgp - 3Com MSR 50 Series Configuration Manual

3 The GR session between the GR Restarter and its peer goes down when the GR
Restarter restarts BGP. The GR capable peer will mark all routes associated with the
GR Restarter as stale. However, during the configured GR Time, it still uses these
routes for packet forwarding, ensuring that no packet will be lost when routing
information from its peer is recollected.
4 After the restart, the GR Restarter will reestablish a GR session with its peer 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 with stale routing information removed. Thus the BGP
routing convergence is complete.

MP-BGP

Overview
The legacy BGP-4 supports IPv4, but does not support some 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), which is defined in RFC2858.
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, namely NLRI, NEXT_HOP and
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 available
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routes and next hops
MP_UNREACH_NLRI: Multiprotocol Unreachable NLRI, for withdrawing
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unfeasible routes
The above two attributes are both Optional non-transitive, so BGP speakers not
supporting multi-protocol ignore the two attributes, not forwarding them to
peers.
Address family
MP-BGP employs address family 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, IPv6
extension. Different extensions are configured in respective address family view.
n
For information about the VPN extension application, refer to
■
Configuration" on page
For information about the IPv6 extension application, refer to
■
Configuration" on page
This chapter gives no detailed commands related to any specific extension
■
application in MP-BGP address family view.
1459.
1015.
BGP Overview 839
"MPLS L3VPN
"IPv6 BGP