Which AS path regular expression will only match a route originating in AS 500 with the last traversing AS of 100?
A. "$100 .* ^500"
B. "500 .*"
C. "^100 .* 500$"
D. "^100 .*"
3 Comments on “Which AS path regular expression will only match a route originating in AS 500 with the last traversing AS of ”
traffikatorsays:
The first indicator that C is wrong is ^. It means starting AS. $means ending AS. A is the correct choice.
BGP AS path is read from right to left meaning the right most AS is the beginning and the left is the final.
The first indicator that C is wrong is ^. It means starting AS. $means ending AS. A is the correct choice.
BGP AS path is read from right to left meaning the right most AS is the beginning and the left is the final.
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http://www.juniper.net/techpubs/en_US/junos9.5/information-products/topic-collections/config-guide-policy/policy-configuring-as-path-regular-expressions-to-use-as-routing-policy-match-conditions.html
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“C” has to be correct answer…regular expressions are matched not on the way its read but on how the “show bgp summary” output is displayed.
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