Reference Guide

Border Gateway Protocol IPv4 (BGPv4) | 323
Command Modes
ROUTER BGP
Usage
Information
This command is a knob to disable BGP next-hop resolution via BGP learned routes.
During the next-hop resolution, only the first route that the next-hop resolves through
is verified for the route’s protocol source and is checked if the route is learned from
BGP or not.
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
Command
History
bgp regex-eval-optz-disable
c e s
Disables the Regex Performance engine that optimizes complex regular expression
with BGP.
Syntax
bgp regex-eval-optz-disable
To re-enable optimization engine, use the no bgp regex-eval-optz-disable command.
Defaults
Enabled by default
Command Modes
ROUTER BGP (conf-router_bgp)
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.
clear ip bgp Description.
Version 8.3.19.0 Introduced on the S4820T.
Version 8.3.7.0 Introduced on the S4810.
Version 7.8.1.0 Introduced support on S-Series
Version 7.7.1.0 Introduced support on C-Series
Version 7.2.1.0 Introduced