hi everyone, i was reading ccie exam cert bt wendell odom and got confused in one of its examples. its from page 435 table 13-5.
reg exp is ^123_.*_45$
"An AS_PATH beginning with AS 123 and ending in AS 4, with atleast one other AS in between."
i think its bit wrong coz . is followed by * which means zero or more occurence of the preceding character now if there is no character between 123 and 45 then its also valid isnt it ? so why its saying that atleast one AS between them ?
am i wrong in my understanding ? kindly tell me.
Theoretically speaking you are right, ".*" means zero or more, but the fact that you have "_" before and after it, and thus this regular expression can't match 123 45, as this one has only one space between the 2 ASs, then practically this regexp will only match when there is at lease one AS in between.