OR .. a matter of a regular experssion

Hello folks,
The previous post of "Matter of a Regular Expression" was providing a simple
format to match AS of the customers and their customer ^100_[0-9]*$
which could also be extended for a 3rd level AS just as easy ^100_[0-9]_[0-9]*$

Now what if the scenario asks you to match Networks originating from AS:255
simple : match on _255$

So what if it asks to also match on Networks originating from AS:256
also simple : create a 2 line as-path ACL
AS path access list 1
    permit _255$
    permit _256$

in the LAB they might try to make it harder and ask you to make it a single
line entry
hmmm :-|

You have got to notice the sequence and try something like this
AS path access list 1
    permit _25[56]$

I admit I was not able to think of that the first time I saw it either
But Lets be more generic
What if it asks you to permit Networks originating from AS:123 and AS:789
and of course using a single line Entry to make it fun

What do you guys think of taking advantage of the "|"
AS path access list 1
    permit _123$|_789$

I think it works but I am not sure if it has any other complications I am not
aware of

So do you think it would work ?

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Received on Wed Apr 15 2009 - 01:00:48 ART