[c-nsp] Filtering Routes with Private AS Numbers in the AS Path

[Ivan]

Hi,

For filtering private as numbers (64512-65535) using an as-path
access-list there are a few options I have seen:

1). All in one line
ip as-path access-list 66 permit
_(6451[2-9]|645[2-9][0-9]|64[6-9][0-9][0-9]|65[0-4][0-9][0-9]|655[0-2][0-9]|6553[0-5])_

2). The above modified hopefully to be "better" in terms or regexp
processing but perhaps not readability
ip as-path access-list 66 permit
_6(4(5(1[2-9]|[2-9][0-9])|[6-9][0-9][0-9])|5([0-4][0-9][0-9]|5([0-2][0-9]|3[0-5])))_

3). Separate lines
ip as-path access-list 66 permit _6451[2-9]_
ip as-path access-list 66 permit _645[2-9][0-9]_
ip as-path access-list 66 permit _64[6-9][0-9][0-9]_
ip as-path access-list 66 permit _65[0-4][0-9][0-9]_
ip as-path access-list 66 permit _655[0-2][0-9]_
ip as-path access-list 66 permit _6553[0-5]_

I would appreciate any feedback as to which is the least CPU intensive and
if there is a better way to optimise 2 above.

Thanks

Ivan