For example, if "show ip bgp 100.1.1.0" shows AS-path (65001 65002) 111 222 333 444 555, AS 555 would be the orinigating AS. When using regular expression, should I make 555 as the beginning of the string or end of the string?
end of the string.
With 65001 and 65002 as IBGP confederation AS, can I use regular expression to specify them or only true EBGP AS can be in regular expression?
You can specify them.
Same explame, if show ip bgp shows community values 111:10 222:20 333:30 etc, which one is considered as the begining of the string?
110:10