Reference Guide

Command History
Version Description
9.9(0.0) Introduced on the C9010.
9.2(1.0) Introduced on the Z9500.
8.2.1.0 Introduced on the E-Series ExaScale.
7.6.1.0 Introduced
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 enabled and active routing protocols.
bgp router-id
Assign a user-given ID to a BGP router.
C9000 Series
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 you do not
configure Loopback interfaces, 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 C9010.
9.2(1.0) Introduced on the Z9500.
8.2.1.0 Introduced on the E-Series ExaScale.
544
Border Gateway Protocol