Dell Brocade DCX, Configuration Manual

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BigIron RX Series Configuration Guide 795
53-1001810-01
Filtering
26
If you want to filter for a special character instead of using the special character as described in
Table 26.2 on page 26-45, enter “\” (backslash) in front of the character. For example, to filter on
AS-path strings containing an asterisk, enter the asterisk portion of the regular expression as “\*”.
BigIron RX(config-bgp)# ip as-path access-list acl2 deny \*
To use the backslash as a string character, enter two slashes. For example, to filter on AS-path
strings containing a backslash, enter the backslash portion of the regular expression as “\\”.
BigIron RX(config-bgp)# ip as-path access-list acl2 deny \\
Filtering communities
You can filter routes received from BGP4 neighbors based on community names.
_ An underscore matches on one or more of the following:
•
, (comma)
•
{ (left curly brace)
•
} (right curly brace)
•
( (left parenthesis)
•
) (right parenthesis)
•
The beginning of the input string
•
The end of the input string
•
A blank space
For example, the following regular expression matches on “100” but not on “1002”, “2100”,
and so on.
_100_
[ ] Square brackets enclose a range of single-character patterns. For example, the following
regular expression matches on an AS-path that contains “1”, “2”, “3”, “4”, or “5”.
[1-5]
You can use the following expression symbols within the brackets. These symbols are allowed
only inside the brackets.
•
^ – The caret matches on any characters except the ones in the brackets. For example,
the following regular expression matches on an AS-path that does not contain “1”, “2”,
“3”, “4”, or “5”.
[^1-5]
•
- The hyphen separates the beginning and ending of a range of characters. A match
occurs if any of the characters within the range is present. See the example above.
| A vertical bar (sometimes called a pipe or a “logical or”) separates two alternative values or
sets of values. The AS-path can match one or the other value. For example, the following
regular expression matches on an AS-path that contains either “abc” or “defg”.
(abc)|(defg)
NOTE: The parentheses group multiple characters to be treated as one value. See the
following row for more information about parentheses.
( ) Parentheses allow you to create complex expressions. For example, the following complex
expression matches on “abc”, “abcabc”, or “abcabcabcdefg”, but not on “abcdefgdefg”.
((abc)+)|((defg)?)
TABLE 117 BGP4 special characters for regular expressions (Continued)
Character Operation