When you configure a peer to support IPv4 multicast, the system takes the following actions:
• Send a capability 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MP_REACH_NLRI and MP_UNREACH_NLRI, for feasible and withdrawn routes, respectively.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 Dell Networking OS 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 Dell
Networking OS 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
The Dell Networking OS 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]
• View information about BGP route being dampened.
EXEC Privilege mode
debug ip bgp dampening [in | out]
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Border Gateway Protocol IPv4 (BGPv4)
