Regular expression table
Regular expressions are strings of special characters that can be used to search and find character patterns. Within the scope of BGP in Cisco IOS regular expressions can be used in show commands and AS-Path access-lists to match BGP prefixes based on the information contained in their AS-Path.
| Term | Description |
|---|---|
| values | A single or series of character sequences within double-quotes ( " ), e.g. "108" for a single character sequence or "108 110 120" for a series of charater sequences. |
| Ranges | A sequence of characters within square brackets [1-4] or [1234] |
| . | Matches any single character. |
| * | Matches 0 or more sequences of the pattern |
| ^ | Matches the beginning of an input string |
| $ | Matches the end of an input string |
| \character | Matches the character. |
| _ | Matches a comma, left brace, right brace, the beginning of an input string, the end of an input string, or a space |
| + | Matches 1 or more sequences of a character |
You can match many criteria Autonomous systems using the show ip bgp regexp. If you would like to practice via the command line and have no router access you can use one of the BGP looking glass servers.
Have fun with online full BGP table http://www.lookinglass.org/
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