Service Manual

Usage Information
BGP uses regular expressions (regex) to filter route information. In particular, the use of regular expressions to
filter routes based on AS-PATHs and communities is quite common. In a large scale configuration, filtering millions
of routes based on regular expressions can be quite CPU intensive, as a regular expression evaluation involves
generation and evaluation of complex finite state machines.
BGP policies, containing regular expressions to match as-path and communities, tend to use a lot of CPU
processing time, which in turn affects the BGP routing convergence. Additionally, the show bgp commands,
which are filtered through regular expressions, use up CPU cycles particularly with large databases. The Regex
Engine Performance Enhancement feature optimizes the CPU usage by caching and reusing regular expression
evaluation results. This caching and reuse may be at the expensive of RP1 processor memory.
Related Commands show ip protocols — views information on all routing protocols enabled and active.
bgp router-id
Assign a user-given ID to a BGP router.
Syntax
bgp router-id ip-address
To delete a user-assigned IP address, use the no bgp router-id command.
Parameters
ip-address Enter an IP address in dotted decimal format to reset only that BGP neighbor.
Defaults The router ID is the highest IP address of the Loopback interface or, if no Loopback interfaces are configured, the
highest IP address of a physical interface on the router.
Command Modes ROUTER BGP
Command History
Version Description
9.9(0.0) Introduced on the FN IOM.
9.2(0.0) Introduced on the MXL 10/40GbE Switch IO Module.
Usage Information Peering sessions are reset when you change the router ID of a BGP router.
bgp soft-reconfig-backup
Use this command only when route-refresh is not negotiated between peers to avoid having a peer re-send BGP updates.
Syntax
bgp soft-reconfig-backup
To return to the default setting, use the no bgp soft-reconfig-backup command.
Defaults Off
Command Modes ROUTER BGPV6 ADDRESS FAMILY (conf-router_bgpv6_af)
Command History
Version Description
9.9(0.0) Introduced on the FN IOM.
9.2(0.0) Introduced on the MXL 10/40GbE Switch IO Module.
646 IPv6 Border Gateway Protocol (IPv6 BGP)