ISP's use IGP's (be they OSPF or IS-IS) for internal reachability (IBGP peering is
generally done on loopbacks and these networks need to be advertised) and for next hop
resolution. Hence, all the perimeter BGP next hops will be advertised into the IGP so
that all IBGP speakers can properly post BGP routes to their routing tables.
In general, very little from BGP enters into an IGP.
Pete
*********** REPLY SEPARATOR ***********
On 11/16/2000 at 3:41 PM Jack Walker wrote:
>I am not familiar with the ISP enviroment at all.
>
>When we say UUNet uses IS-IS on their core, do we mean that they
>redistribute their BGP routes from their edge routers into IS-IS and
>redistribute back into BGP and the far end edge routers?
>Which means the edge routers are running BGP to learn customers' routes and
>redistribute these routes into IS-IS to router across the UUNet core? Just
>want to verify that I understand this correctly.
>
>Thanks
>
>Jack
>
>
>"Priscilla Oppenheimer" <[EMAIL PROTECTED]> wrote in message
>[EMAIL PROTECTED]">news:[EMAIL PROTECTED]...
>> At 09:38 AM 11/16/00, Spolidoro, Guilherme wrote:
>>
>> >UUNet for example uses IS-IS on their core while the rest (or the
>majority)
>> >of the ISPs use OSPF. I wonder why UUNet chosed for IS-IS instead of
>OSPF.
>> >Maybe somebody on the list has an answer?
>> >
>> >Today I would chose OSPF over IS-IS because:
>> >
>> >- much more vendors support OSPF compared to IS-IS
>> >- it's my perception that OSPF is the direction chosen by IETF,
>>
>>
>> A few years ago a bunch of people wore T-shirts to an IETF meeting that
>> said, "IS-IS=0." They did this to bug Radia Perlman. &;-) It didn't work.
>> These days the IETF seems to do a lot of work on both IS-IS and OSPF. For
>a
>> while it looked like we could get by without knowing IS-IS. I don't think
>> that's true anymore. The pendulum has swung back in its favor.
>>
>> Priscilla
>>
>>
>>
>> ________________________
>>
>> Priscilla Oppenheimer
>> http://www.priscilla.com
>>
>> _________________________________
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>
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