RE: BGP REGEXP

:). Sometimes it is like a light turns on. But yes your first point is
correct.

Regards,

Tyson Scott - CCIE #13513 R&S, Security, and SP

Managing Partner / Sr. Instructor - IPexpert, Inc.

Mailto: <mailto:tscott_at_ipexpert.com> tscott_at_ipexpert.com

From: Muzammil Malick [mailto:malickmuz_at_gmail.com]
Sent: Friday, June 25, 2010 3:32 PM
To: Tyson Scott
Cc: Cisco certification
Subject: Re: BGP REGEXP

Hi

Yes I have read the posts you both mentioned already but its like you said I
think I am overthinking it.

I have tried testing this on the router servers and this is what I see

sh ip bgp regexp ^[0-9]$

I did not get a result from this and I expected this, because what i
understand from this expression is that it will only match routes with 1
single digit AS number.

Am i right in thinking this?

To prove this I used the following

sh ip bgp regexp ^[0-9]+$

This showed me all routes with a single AS number with any amount of digits.

As long as I am right on my first point then I think I understand this now.
I was having difficulty understand that the + operator could be used any
number of times for any number (even though that's what it says on the tin)

Thanks

On 25 June 2010 19:50, Tyson Scott <tscott_at_ipexpert.com> wrote:

0-9 means any number between 0 and 9 occurring one or more times. Meaning
any number in any combination.

If you wanted specific numbers it would be something like

[5|6][4|5]

for example would only match

54, 55, 64, 65

Regards,
 
Tyson Scott - CCIE #13513 R&S, Security, and SP
Managing Partner / Sr. Instructor - IPexpert, Inc.
Mailto: tscott_at_ipexpert.com

-----Original Message-----
From: nobody_at_groupstudy.com [mailto:nobody_at_groupstudy.com] On Behalf Of
Muzammil Malick
Sent: Friday, June 25, 2010 2:37 PM
To: Cisco certification
Subject: BGP REGEXP

Hi Guys

Can someone help me out here?

I have always struggled with my understanding of regexp but I WANT to
understand them desperately.
I have to hang my head in shame because I have read a lot of posts out there
but still keep getting confused.

For example

the "+" operator. As far as I can understand this means 1 or more instances.
I have seen this used as follows:

^[0-9]+$ Directly connected AS.

So I tested this using home made lab and sure enough it only shows routes
from directly connected AS'
When I look at this I interpret it as any number between 0-9, and this can
be repeated one ore more times.
e.g 1, 2, 3 or 22, 2222
So how does this match 54, or 65?

Thanks

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Received on Fri Jun 25 2010 - 15:41:45 ART