Administrator Guide
Defaults Enabled.
Command Modes ROUTER BGP
Command
History
Version Description
9.9(0.0) Introduced on the C9010.
9.2(1.0) Introduced on the Z9500.
8.2.1.0 Introduced on the E-Series ExaScale.
7.4.1.0 Introduced
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
clear ip bgp
bgp regex-eval-optz-disable
Disables the Regex Performance engine that optimizes complex regular expression with BGP.
C9000 Series
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
9.9(0.0) Introduced on the C9010.
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 449