Administrator Guide

The clear ip bgp command is required for this command to take effect and to keep the BGP database
consistent. Execute the clear ip bgp command right after executing this command.
Related
Commands
clear ip bgp
bgp regex-eval-optz-disable
Disables the Regex Performance engine that optimizes complex regular expression with BGP.
C9000 Series
Syntax
bgp regex-eval-optz-disable
To re-enable optimization engine, use the no bgp regex-eval-optz-disable command.
Defaults Enabled.
Command Modes ROUTER BGP (conf-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.
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.
Border Gateway Protocol 425