[quagga-users 14805] Re: BGP type 2 length 3294 is too large, attribute total length is 2314.

On Sat, Sep 09, 2017 at 07:30:39AM +0200, Andreas Jaggi wrote:
> Hi Matthias
> 
> We are using the following approach:  ip as-path access-list limit-to-100 deny ^([0-9]+ ){99,}[0-9]+$

thanks! apparently I forgot the '+' sign after the digits when testing
the {} construct, and there are only so many single-digit ASes or long
AS paths made of single-digit ASes :-)

I used '_' (underscore) instead of ' ' (space). Underscore also matches
'{', ',' and '}' (confederation syntax?) and beginning and end of
string. But still my regex failed to match anything using '{' in the AS
path. Matching that would require '_+' as separator and a comma in the
character set.

E.g. 217.199.156.0/22 ends in 16637 9129 {64237,64512,65008,65011,65400}

I think your regex also misses that.

I now use this format:

    ip as-path access-list maxas-limit75 deny ^([{},0-9]+ ){75}

This counts {a,b,c} path elements as a single entry, and the blank
requires that there is still something more following the list of 75
ASes.


Regards
Matthias



> 
> Cheers
> Andreas
> 
> 
> On Fri, Sep 08, 2017 at 04:52:47PM +0200, Matthias Ferdinand wrote:
> > Hi,
> > 
> > Cisco IOS seems to have a nice configuration setting
> > 
> >    bgp maxas-path <num>
> > 
> > https://www.cisco.com/c/en/us/td/docs/ios/12_2/iproute/command/reference/fiprrp_r/1rfbgp1.html#wp1254976
> > 
> > which apparently quagga does not have.
> > 
> > So I set up an as-path access-list like so:
> > 
> >     ip as-path access-list maxas-limit75 deny _[0-9]+_[0-9]+_[0-9]+_[0-9]+_[0-9]+_[0-9]+_[0-9]+_[0-9]+_[0-9]+_[0-9]+_[0-9]+_[0-9]+_[0-9]+_[0-9]+_[0-9]+_[0-9]+_[0-9]+_[0-9]+_[0-9]+_[0-9]+_[0-9]+_[0-9]+_[0-9]+_[0-9]+_[0-9]+_[0-9]+_[0-9]+_[0-9]+_[0-9]+_[0-9]+_[0-9]+_[0-9]+_[0-9]+_[0-9]+_[0-9]+_[0-9]+_[0-9]+_[0-9]+_[0-9]+_[0-9]+_[0-9]+_[0-9]+_[0-9]+_[0-9]+_[0-9]+_[0-9]+_[0-9]+_[0-9]+_[0-9]+_[0-9]+_[0-9]+_[0-9]+_[0-9]+_[0-9]+_[0-9]+_[0-9]+_[0-9]+_[0-9]+_[0-9]+_[0-9]+_[0-9]+_[0-9]+_[0-9]+_[0-9]+_[0-9]+_[0-9]+_[0-9]+_[0-9]+_[0-9]+_[0-9]+_[0-9]+_[0-9]+_[0-9]+_[0-9]+_[0-9]+_[0-9]+
> >     ip as-path access-list maxas-limit75 permit .
> > 
> > which seems to work, but is not nice to read. I tried to use counting
> > regexes with braces ([0-9]{0,75}) without success. Is there a more
> > elegant way to do it than above?
> > 
> > Regards
> > Matthias Ferdinand
> 
> -- 
> andreas jaggi
> lead engineer network services
> 
> open systems ag
> raeffelstrasse 29
> ch-8045 zurich
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> 
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