>Sounds like you guys were doing IBGP...
Could be, but there are several other explanations.
Let me go into the underlying rationale. According to RFC1930, which
is a must-read in understanding BGP, an AS is a set of addresses and
routers, under one or more administrations, that presents a common
routing policy to the internet. So, if Dan's employer had Internet
connectivity only through the provider, the customer would logically
be part of the provider's AS.,
Providers are usually reluctant to let customers have access to their
iBGP. You will see cases where the provider controls an iBGP router
at the customer premises.
More likely, the provider assigned a private AS number to the
customer, and either made it part of a confederation or used a rather
undocumented Cisco feature called remove-private-as. By doing this,
you have all the power of eBGP policy controls, but you don't burn a
registered AS number.
I'd like to throw out a related question to people that recently have
taken BGP in a Cisco course, or in certification tests. On this
list, the term "advanced BGP" is used a good deal in relation to the
new material. It had been my experience that the BGP in ACRC was so
oversimplified as to have no relationship with anything one would see
in the ISP world. In particular, there was handwaving about
"policies," but very little about why one has policies or how they
are enforced -- just the urban legend that "BGP carries policies."
I'm doing a series of tutorials on BGP at certificationzone.com, the
second of which is in the free area of the CCIE zone. To me, they
are at the "BGP 101 or BGP 102" level in terms of real-world Internet
operations.
Within what people can say within NDA, are complex AS path
expressions being considered? QoS policy setting based on AS
path/address/community? Hierarchical route reflectors? The flavors
of hard and soft refresh? Load-sharing policies? Cold potato routing?
etc., etc., etc....
What topics that people are seeing in BGP course material or tests on
which you'd most like additional tutorials? Unfortunately, I don't
approach this topic through the eyes of a person starting with the
technology.
>
>-B
>"Dan West" <[EMAIL PROTECTED]> wrote in message
>[EMAIL PROTECTED]">news:[EMAIL PROTECTED]...
> > My former employer (an ISP) had BGP peering with our
> > upstream provider(Telco). As I understand it so far,
> > BGP4 is used to advertise routes between autonomous
> > systems. One day I ran a web-based traceroute to my
> > old haunt and it showed them having the same
> > autonomous system number as our bandwidth provider.
> > Were we unnecessarily using BGP? I don't understand
> > why our telco and we (the ISP) had the same AS number.
> >
> >
> > Am I misunderstanding the purpose of the AS number in
> > BGP?
> >
> > Many thanks.
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