This BGP gizmo looks rather intriguing...Can anyone
recommed ONE comprehensive, well-written book on iBGP
and eBGP?
Many thanks. ( from myself and elgrande.com)
--- "Howard C. Berkowitz" <[EMAIL PROTECTED]> wrote:
> >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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Dan West -- CCNA
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