Administrator Guide
bgp recursive-bgp-next-hop
Enable next-hop resolution through other routes learned by BGP.
C9000 Series
Syntax
bgp recursive-bgp-next-hop
To disable next-hop resolution, use the no bgp recursive-bgp-next-hop command.
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
432 Border Gateway Protocol