[c-nsp] prefixes in AS-Set

[Martin T]

As I understand, in case ISP-A would like to peer with ISP-B, the
ISP-A usually specifies it's AS-set it will announce to ISP-B? For
example in case XS4ALL(xs4all.nl) would like to set up a peering with
some other ISP, it will announce AS-ACCESSFORALL, which contains all
XS4ALL ASN's. ISP-B should be able to find all those ASN's which are
under the AS-set called AS-ACCESSFORAL by:

$ whois AS-ACCESSFORALL | grep member
members:        AS3265
members:        AS1200
members:        AS5417
members:        AS8283
members:        AS20689
members:        AS33955
$

Now if ISP-B is interested in all the prefixes which are under those
ASN's it could do "whois -h whois.ripe.net -i origin <ASN>" with every
ASN under the AS-ACCESSFORAL and manually write the addresses down or
do:

peval AS-ACCESSFORALL | sed 's/({//;s/})//;s/, /\n/g' | aggregate -q

This last command would give:

$ peval AS-ACCESSFORALL | sed 's/({//;s/})//;s/, /\n/g' | aggregate -q
46.21.224.0/20
46.23.80.0/20
62.216.0.0/19
62.251.0.0/17
77.73.16.0/21
80.100.0.0/15
80.126.0.0/15
81.24.0.0/20
82.92.0.0/14
82.161.0.0/16
83.68.0.0/19
83.160.0.0/14
91.200.16.0/22
91.208.34.0/24
94.142.240.0/21
95.129.120.0/21
193.104.193.0/24
193.110.157.0/24
193.111.228.0/24
194.109.0.0/16
194.159.72.0/23
194.159.224.0/21
194.217.220.0/22
195.11.224.0/19
195.64.80.0/20
195.69.144.0/22
195.95.150.0/24
195.173.224.0/19
212.238.0.0/16
213.84.0.0/16
213.222.0.0/19
217.194.16.0/21
$

So in case XS4ALL announces it's AS-set AS-ACCESSFORALL(it seems to be
the only AS-set for company XS4ALL) to ISP-B, the latter would receive
all those prefixes above over the established BGP session.

Have I understood this whole concept correctly? Any additional
notes/corrections are most welcome!

It's not directly Cisco-related question, but hopefully not off-topic as well :)


regards,
martin