BGP Regular Expression for 64512-65535 (Private ASs)

[kfarrington]

Is there a regexp for BGP private ASs.

I would like to put them in an expanded community-list?

Many kind regards,

Ken

[Harold Ritter]

I'm not sure I understand your question. regexp works for all ASNs. Could you please clarify your question.

Thanks,

[kfarrington]

Sorry about that,

I want to match a specific community value (a global LP community setting) so when I receive this community value privateas:xxxx i will set the attribute.

So, if we had a private AS range in the following regions set

Region AS Range

Region1 64600 – 64899

Region2 64900 – 65199

region3 65200 – 65535

if I receive a community value of any of the above ASs with a :123 i will set LP to 95.

ip community-list expanded companyASs permit ^64[6-9][0-9][0-9]$:123

ip community-list expanded companyASs permit ^65[0-4][0-9][0-9]$:123

ip community-list expanded companyASs permit ^655[0-2][0-9]$:123

ip community-list expanded companyASs permit ^6553[0-5]$:123

Is there a way to use regular expressions to match all of these ASs in one line and thus cut the config down?. I am not a big regexp master?

Kind regards,

Ken

[kfarrington]

I have just seen the OR funtion

no ip community-list expanded companyASs

ip community-list expanded companyASs permit _64[6-9][0-9][0-9]:123_|_65[0-4][0-9][0-9]:123_|_655[0-2][0-9]:123_|_6553[0-5]:123_

but funny how the ^ and $ donot work with the or function

no ip community-list expanded companyASs

ip community-list expanded companyASs permit ^64[6-9][0-9][0-9]:123$|^65[0-4][0-9][0-9]:123$|^655[0-2][0-9]:123$|^6553[0-5]:123$

I like using the carrat dollar, but dont thin I can, unless anyone knows to the contary?

Best regards as always,

Ken

[Harold Ritter · Accepted solution]

Ken,

You need to specify the ^ and $ only at the beginning and at the end. The following community-lists should do what you want.

R1#sh ip community-list

Named Community expanded list group1

permit ^64[6-8][0-9][0-9]:123$

Named Community expanded list group2

permit ^649[0-9][0-9]:123|65[0-1][0-9][0-9]:123$

Named Community expanded list group3

permit ^65[2-5][0-9][0-9]:123$

Hope this helps,

[kfarrington]

thx, thats gr8 fella.

many thx as usual :)

[aravindhs]

Hi hritter,

Shouldn't the last one be

^65[2-5][0-3][0-5]:123$

The below range is what Ken was looking at, right ?

region3 65200 – 65535

Regards

Arav.

[Harold Ritter]

Your regexp only allows 65200 to 65235, 65300 to 65335, 65400 to 65435 and 65500 to 65535.

The regular expression I suggested (65[2-5][0-9][0-9]) allows 65200 to 65599 but no community can be larger than 65535 anyway.

Hope this helps,

[kfarrington]

Quick one just to end up with on this is.

can we just have a community-list that either says :-

ip community-list standard/expanded permit range 64512 65535

or

ip community-list standard/expanded permit private-as-range

:)

man, could i raise a feature request for it?

if it was that easy though, we would all be out on our ears :))

many thx to all for their input :)

the pub opens in 2h4m - cant wait!!

[Harold Ritter]

I guess it would be nice to call the private AS range by name just like we do for the internet, local-AS, no-advertise and no-export communities.

Please have a pint for me ;o)

[mmolina10855]

Hello,

This subject has probably been beaten to death but I looked into the same issue about a year ago and this is the one line regular expression that somebody suggested that seemed to work just fine:

_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]_

I know it is bordering on ridiculous but it works :-)

[chgallup]

BGP Regular Expression for 64512-65535 (Private ASs)

this is for 16bit private ASs

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])_

so

so this regex 64[5-9][0-9][0-9]|65[0-5][0-9][0-9] won't work with 32bit private AS's)