Reference Guide
Defaults Enabled.
Command Modes ROUTER BGP
Command History
Version 8.2.1.0 Introduced on the E-Series ExaScale.
Version 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.
C-Series, E-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 8.2.1.0 Introduced on the E-Series ExaScale.
Version 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 routing protocols enabled and active on the E-
Series.
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