This blog was originally started to better help me understand the technologies in the CCIE R&S blueprint; after completing the R&S track I have decided to transition the blog into a technology blog.

CCIE #29033

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Monday, May 24, 2010

Question 122

What does "bgp regexp deterministic" accomplish?

1 comments:

Packets Analyzed said...

There are 2 regular expression engines the "default" and a "new" engine that can process complex regular expressions.

Default Regular Expression Engine
- Uses recursive algorithm
- As the complexity of regular expressions increases the more system resources are required
- Works well for simple regular expressions

New Regular Expression Engine Selection
- new engine does not replace the default regular expression engine
- improved algorithm
- greatly improved performance when processing complex regular expressions
- complex regular expressions are evaluated more quickly
- takes longer to process simple regular expressions than the default engine.

Cisco recommends using the regular expression engine that fits your environemnt. New engine for complex regular expressions and default for simple regular expressions.

To enable the New engine type the following under the BGP process.

"bgp regexp deterministic"

To enable the Default engine after enabling the New prefix the command with "no" EX:

"no bgp regexp deterministic"

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