Reference Guide

238 | Border Gateway Protocol IPv4 (BGPv4)
www.dell.com | support.dell.com
Dell Networking OS MBGP is implemented as per RFC 1858. The MBGP feature can be enabled per
router and/or per peer/peer-group.
Default is IPv4 Unicast routes.
When a peer is configured to support IPv4 Multicast, Dell Networking OS 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 will mark 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MP_REACH_NLRI and MP_UNREACH_NLRI, for feasible and withdrawn routes, respectively.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. Refer to the Dell Command Line Interface Reference for a detailed
description of the MBGP commands.
BGP Regular Expression Optimization
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. 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 the CP processor. This feature is turned on
by default. Use the command
bgp regex-eval-optz-disable in CONFIGURATION ROUTER BGP mode
to disable it if necessary.
Debugging BGP
Use any of the commands in EXEC Privilege mode to enable BGP debugging.
Command Syntax Command Mode Purpose
address family ipv4
multicast
CONFIG-ROUTER-BGP
Enables support for the IPv4 Multicast
family on the BGP node
neighbor [ip-address |
peer-group-name] activate
CONFIG-ROUTER-BGP-AF
(Address Family)
Enable IPv4 Multicast support on a BGP
neighbor/peer group
Command Syntax Command Mode Purpose
debug ip bgp [ip-address | peer-group
peer-group-name] [in | out]
EXEC Privilege View all information on BGP, including BGP
events, keepalives, notifications, and updates.