Routing TCP/IP, Volume II (CCIE Professional Development)

Appendix B. A Regular-Expression Tutorial

This tutorial follows the excellent presentation made by Jeffrey E. F. Friedl in his book Mastering Regular Expressions. The book is listed as recommended reading at the end of this appendix, although almost everything you need to know about regular expressions (regex) to work with Cisco IOS Software is covered in the very first chapter of the book. Nonetheless, the book recommendation stands because you are very likely to find regular expressions useful in a wide variety of applications within the data communications and data processing industry. Friedl presents the subject clearly and with a liberal dose of humor.

Literals and Metacharacters

A typical AS_PATH filter might look like this:

ip as-path ...