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• #2784 zsolti.22 senior tag

  Új Válasz 2012-12-18 11:26:01 #2784

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  zsolti.22

  senior tag

  Van nekem egy csodás regexp részem a BGP-nél, amit ha még le is fordítanák, nem biztos, hogy jó lenne/megérteném. Tud segíteni egy regexpeket sokat használó emberke megérteni ezeket?

  AS regular expression

  This section explains the creation of a regular expression.
  A regular expression is a pattern to match against an input string. When you build a regular expression, you specify a string that input must match. In the case of BGP, you specify a string that consists of path information that an input must match.
  In the example in the section Path Filtering, you specified the string ^200$. You wanted path information that comes inside updates to match the string in order to make a decision.
  A regular expression comprises:
  • Range
  A range is a sequence of characters within left and right square brackets. An example is [abcd].
  • Atom
  An atom is a single character. Here are some examples:
  .
  • The . matches any single character.
  ^
  • The ^ matches the start of the input string.
  $
  • The $ matches the end of the input string.
  \
  • The \ matches the character.
  -
  • The _ matches a comma (,), left brace ({), right brace (}), the start of the input string, the end of the input string, or a space.
  • Piece
  A piece is one of these symbols, which follows an atom:
  *
  • The * matches 0 or more sequences of the atom.
  +
  • The + matches 1 or more sequences of the atom.
  ?
  • The ? matches the atom or the null string.
  • Branch
  A branch is 0 or more concatenated pieces.
  Here are some examples of regular expressions:
  a*
  • This expression indicates any occurrence of the letter "a", which includes none.
  a+
  • This expression indicates that at least one occurrence of the letter "a" must be present.
  ab?a
  • This expression matches "aa" or "aba".
  _100_
  • This expression means via AS100.
  _100$
  • This expression indicates an origin of AS100.
  ^100 .*
  • This expression indicates transmission from AS100.
  ^$
  • This expression indicates origination from this AS.
  Refer to Using Regular Expressions in BGP for sample configurations of regular expression filtering.

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