Reference Guide
Enabling MBGP Configurations
Multiprotocol BGP (MBGP) is an enhanced BGP that carries IP multicast routes. BGP carries two sets of routes: one set
for unicast routing and one set for multicast routing. The routes associated with multicast routing are used by the
protocol independent multicast (PIM) to build data distribution trees.
MBGP for IPv4 multicast is supported on the S4820T platform.
FTOS MBGP is implemented per RFC 1858. You can enable the MBGP feature per router and/or per peer/peer-group.
The default is IPv4 Unicast routes.
When you configure a peer to support IPv4 multicast, FTOS takes the following actions:
• Send a capacity advertisement to the peer in the BGP Open message specifying IPv4 multicast as a supported
AFI/SAFI (Subsequent Address Family Identifier).
• If the corresponding capability is received in the peer’s Open message, BGP marks the peer as supporting the
AFI/SAFI.
• When exchanging updates with the peer, BGP sends and receives IPv4 multicast routes if the peer is marked as
supporting that AFI/SAFI.
• Exchange of IPv4 multicast route information occurs through the use of two new attributes called
MP_REACH_NLRI and MP_UNREACH_NLRI, for feasible and withdrawn routes, respectively.
• If the peer has not been activated in any AFI/SAFI, the peer remains in Idle state.
Most FTOS BGP IPv4 unicast commands are extended to support the IPv4 multicast RIB using extra options to the
command. For a detailed description of the MBGP commands, refer to the
FTOS Command Line Interface Reference
Guide
.
• Enables support for the IPv4 multicast family on the BGP node.
CONFIG-ROUTER-BGP mode
address family ipv4 multicast
• Enable IPv4 multicast support on a BGP neighbor/peer group.
CONFIG-ROUTER-BGP-AF (Address Family) mode
neighbor [ip-address | peer-group-name] activate
BGP Regular Expression Optimization
FTOS optimizes processing time when using regular expressions by caching and re-using regular expression evaluated
results, at the expense of some memory in RP1 processor.
BGP policies that contain regular expressions to match against as-paths and communities might take a lot of CPU
processing time, thus affect BGP routing convergence. Also, show bgp commands that get filtered through regular
expressions can to take a lot of CPU cycles, especially when the database is large.
This feature is turned on by default. If necessary, use the bgp regex-eval-optz-disable command in
CONFIGURATION ROUTER BGP mode to disable it.
Debugging BGP
To enable BGP debugging, use any of the following commands.
• View all information about BGP, including BGP events, keepalives, notifications, and updates.
EXEC Privilege mode
debug ip bgp [ip-address | peer-group peer-group-name] [in | out]
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