Command Line Reference 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.
Z9500
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
9.2(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.
Border Gateway Protocol
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