Administrator Guide

Version Description
9.2(1.0) Introduced on the Z9500.
8.3.19.0 Introduced on the S4820T.
8.3.11.1 Introduced on the Z9000.
8.3.7.0 Introduced on the S4810.
7.8.1.0 Introduced on the S-Series.
7.7.1.0 Introduced on the C-Series.
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 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 much 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.
Examples
Dell(conf-router_bgp)# no bgp regex-eval-optz-disable
Dell(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
Dell(conf-router_bgp)#
Related
Commands
show ip protocols — views information on all routing protocols enabled and active on the E-Series.
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 no Loopback interfaces are configured, the
highest IP address of a physical interface on the router.
Command Modes ROUTER BGP
Border Gateway Protocol 331