Ascend Archive
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Re: (ASCEND) Multiple feed questions
At 11:06 AM 6/19/98 -0500, you wrote:
>- If I use two completely different upstream ISP's, how does routing work
>on my end? RIP, OSPF?
Avi Freedman has written about this quite extensively. here is a URL for a
NANOG paper:
http://www.academ.com/nanog/october1997/iq/index.html
will get you started. his view is cisco-oriented, but useful. also of value
are some of Harold Berkowitz's stuff is quite relevant, too:
http://www.academ.com/nanog/feb1998/multihoming.html
you have two approaches. you can either speak BGP4 to both providers, and
use your choice of (RIP, OSPF) internally, or...
you can use alternative approaches, which generally involve playing some
games. for example, one might run OSPF internally, and use RIP to talk to
the two upsteams. you need to register for an ASN (get one from ARIN, cost
is $500 one time). you also need both upstreams to be cooperative and
reasonably hands on, as there will be some tuning and tweaking involved,
and some special case things to do like having them tag your routes with
your ASN when they advertise them.
officially, BGP4 is the way you're supposed to do this stuff, but the "RIP
to Upsteams" trick can be gotten to work with a little care and cooperative
upstreams. you use RIP in this case primarily so that when one of the two
Ts drops, the advertisements are pulled from the BGP advertisements of the
upstream in question.
Ascend relevance? the only Ascend product that does BGP4 is the GRF; if you
are using Pipelines to talk to your upstream, or if they're bringing in
your line through a MAX, then you need to evaluate the non-BGP4 solutions
to the multi-homing problem (be forewarned that the Cisco 2501, while it
can talk BGP4, isn't really a good router to use for multi-homed,
multi-full-T1 BGP4 operations, so factor that one out of any decision
making process. also be aware that if your upstream is using a MAX, but has
a BGP4 capable router in the rack next to it, then the MAX can simply
forward packets into the big router, so that problem has a usable work
around.)
cheers,
richard
--
Richard Welty
NeWorks Networking, Inc. 518-244-9675
rwelty@neworks.net http://www.neworks.net/
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