Deployment Guide

Border Gateway Protocol IPv4 (BGPv4) | 343
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.
Related
Commands
Command
History
Example
Figure 12-2. Command Example: no bgp regex-eval-optz-disable
bgp retain-ibgp-nexthop
c e s
BGP does not update the NEXT_HOP attribute if it is a Route-Reflector. Use this command to retain
the NEXT_HOP attribute when advertising to internal BGP peer.
Syntax
bgp retain-ibgp-nexthop
Defaults
Disabled
show ip protocols View information on all routing protocols enabled and active on the E-Series.
Version 7.8.1.0 Introduced support on S-Series
Version 7.7.1.0 Introduced support on C-Series
Version 7.6.1.0 Introduced
(conf-router_bgp)#no bgp regex-eval-optz-disable
(conf-router_bgp)#do show ip protocols
Routing Protocol is "ospf 22222"
Router ID is 2.2.2.2
Area Routing for Networks
51 10.10.10.0/00
Routing Protocol is "bgp 1"
Cluster Id is set to 10.10.10.0
Router Id is set to 10.10.10.0
Fast-external-fallover enabled
Regular expression evaluation optimization enabled
Capable of ROUTE_REFRESH
For Address Family IPv4 Unicast
BGP table version is 0, main routing table version 0
Distance: external 20 internal 200 local 200
(conf-router_bgp)#
Note: Starting in the C-Series release 8.4.7.0, this command is no longer supported.