You are evaluating a routing policy for an ISP and you find the ^42+ .* (23|9)$ regular expression.Which three AS paths match the regular expression? (Choose three.)
A.
42 42 42 42 9
B.
42 42 23 500
C.
42 42 42 60 9
D.
42 60 23 9 42
E.
42 69 500 23
Which three AS paths match the regular expression?
You are evaluating a routing policy for an ISP and you find the ^42+ .* (23|9)$ regular expression.Which three AS paths match the regular expression? (Choose three.)
Table 1-3 Supported regular expression metacharacters
Metacharacter Description
^ Matches the beginning of the input string.
Alternatively, when used as the first character within brackets—[^ ]—matches any number except the ones specified within the brackets.
$ Matches the end of the input string.
. Matches any single character, including white space.
* Matches 0 or more sequences of the immediately previous character or pattern.
+ Matches 1 or more sequences of the immediately previous character or pattern.
? Matches 0 or 1 sequence of the immediately previous character or pattern.
() Specifies patterns for multiple use when followed by one of the multiplier metacharacters: asterisk *, plus sign +, or question mark ?
[ ] Matches any enclosed character; specifies a range of single characters.
– (hyphen) Used within brackets to specify a range of AS or community numbers.
_ (underscore) Matches a ^, a $, a comma, a space, a {, or a }. Placed on either side of a string to specify a literal and disallow substring matching. Numerals enclosed by underscores can be preceded or followed by any of the characters listed above.
| Matches characters on either side of the metacharacter; logical OR.
It’s useful. Good job.