Administrator Guide
Version Description
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 lter route information. In particular, the use of regular expressions to lter
routes based on AS-PATHs and communities is common. In a large-scale conguration, ltering millions of routes
based on regular expressions can be quite CPU intensive, as a regular expression evaluation involves generation
and evaluation of complex nite state machines.
BGP policies, containing regular expressions to match as-path and communities, tend to use much CPU processing
time, which in turn aects the BGP routing convergence. Additionally, the show bgp commands, which are
ltered 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 — view information on all routing protocols enabled and active on the E-Series.
bgp router-id
Assign a user-given ID to a BGP router.
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 congured, the
highest IP address of a physical interface on the router.
Command Modes ROUTER BGP
Border Gateway Protocol 371