Users Guide

Usage
Information
This command is a knob to disable BGP next-hop resolution using 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 — clears the 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
This guide is platform-specific. For command information about other platforms, refer to the relevant Dell
Networking OS Command Line Reference Guide.
The following is a list of the Dell Networking OS version history for this command.
Version Description
9.9(0.0) Introduced on the C9010.
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"
Border Gateway Protocol 331