This is a good question, and I'd like to pose a question myself to
people who read my response. As far as I am concerned, my answers
here are at the minimum real-world level for Internet routing
operations. I draw a distinction between Internet routing operations
and "BGP".
ACRC was completely useless, IMNSHO, when it came to BGP and the
wider subject of Internet routing operations. There's a lot of
discussion about a new emphasis on BGP in BCSN. From talking to some
BCSN instructors, however, my sense is that the operational issues I
describe below are _not_ considered in the courseware. Am I correct
in that assumption?
Do some current instructors go beyond that level in chalktalks or
supplementary materials?
Aside from personal curiosity and planning the next BGP paper for
CertZone, I have the ulterior motive of writing a proposal for an
Internet Routing book, that is more operational-environment, less
configuration and protocol mechanics oriented than the books out
there now. It would also be multivendor (Cisco, gated/rsd, Bay RS,
JunOS). I'm trying to figure out if these are problems I should write
a book to solve.
>I trying to add redundency to my network at work (I work for a very small
>local ISP) and I'd like to run BGP on this router so that if line A dies to
>upstream provider A, line B will take over to upstream provider B.
>
>What is the least requirement for BGP? Someone told me I needed at least a
>/20 of IP's from ARIN. Someone else told me that I need SWIP instead of
>RWHOIS. So I'm left wondering exactly what is the minimum overall
>requirements to run BGP?
BGP itself does not have any minimum requirement. A decreasing
number of major ISPs, however, filter routes longer than /19 or /20.
If you are homed to at least two upstream providers, with at least T1
speed, you can generally justify your own AS number. That assignment
is independent of your address space; you do not necessarily need
provider-independent address space to get a registered AS.
When requesting an AS, expecting to advertise provider-assigned
space, you will probably need to document that the provider that is
assigning you the address space will advertise your more-specific
assignment as well as their supernet. You will also need to document
that your alternate provider will advertise this same more-specific
block assigned to your primary provider, and the primary provider
consents to the alternate provider advertising it. All this should
be recorded in a route registry as well as in the AS number
application.
As far as the address space, there is a "fast start" procedure at
ARIN. If an ISP can demonstrate efficient use of a /21, and is
growing, it can request a "fast start" /20. This /20 will be one half
of a /19, and you are permitted to advertise the /19 to get through
prefix length filters. You have to agree to justify the full /19 in
18 months, or renumber back into provider assigned space.
Yes, I would agree SWIP is far more widely used than RWHOIS. Check
with ARIN if RWHOIS is acceptable for documenting your address
assignments. SWIP and DNS are part of your routing/address
management.
>
>Maybe I don't need BGP? Maybe a floating static route might also work? Please
>explain and give sample code if possible.
Floating statics can be fine when you have multiple points of
attachment to a single upstream, but it is much more problematic when
connecting to multiple ISPs. The key issue is this: how does the
secondary provider know whether or not to advertise your block if it
doesn't have a routing protocol to let it know when the route between
you is active?
>Thanx in advance,
>
>Ken
>
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