Enterasys-networks Security Router X-PeditionTM Manual de usuario descargar pdf (Pagina 161)

Overview

XSR User’s Guide 6-13

• Set community attributes for a specific route with set community

• Set the origin for a specific route with set origin

• Set the MED of a specific route with set metric

• Set the local preference for a specific route with set local-preference

• Set the AS-Path list for a specific route with set as-path

• Set the dampening parameters for a specific route with set dampening

• Set the next hop IP address for a specific route with set ip next-hop

Regular Expressions

Regular expressions commonly notate text string patterns. They specify rules for a set of strings

you may want to match in a search. With BGP, regular expressions search AS paths to match a

particular pattern and are especially useful in building complex policies. Regular expressions are

evaluated from left to right in sequence with binary logic. A number denotes a literal numeral and

AS number. Special characters denote position or operation within a string.

Regular Expression Characters

• 0 through 9 numerals are literals, used in any combination to represent an AS number

• '^' marks the beginning of a path

• '$' marks the end of a path

• '{' marks the beginning of an AS_SET

• '}' marks the end of an AS_SET

• '(' marks the start of an AS_CONFED_SET or AS_CONFED_SEQ

• ')' marks the end of an AS_CONFED_SET or AS_CONFED_SEQ

To match AS numbers in an AS path, use any of the following expressions:

– '.' Matches any valid AS number

– '.*' matches 0 or more sequence or AS numbers

–'.+' matches 1 or more of the sequence of AS numbers

– '_' (underscore) matches 0 or 1 instance of any punctuation character

– [ ] specifies a set of AS numbers or punctuation, for example, “[1234 45 6789]” or “[ {( ]”,

all members of a set must be the same type, i.e. either AS numbers or punctuation

– '-' is used within brackets to specify a range of AS numbers, for example “[23 - 45]”

– '^' when used as the first item within brackets specifies any AS number except the set

specified; for example, to specify any AS number other than 11 or 13 use “[^11 13]”

Regular Expression Examples

The following displays some common examples for matching AS paths using regular expressions

with the

show ip /jointfilesconvert/1254416/bgp regexp command.

• Display all routes with a single AS number in the AS path:

–

show ip /jointfilesconvert/1254416/bgp “.”

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Enterasys-networks Security Router X-PeditionTM Manual de usuario Pagina 161