>Ok. I'm even more confused now. So you guys are saying that IBGP
>peers will never
>progragated its route to other IBGP peers by "no synchronization" -
>if no IGP is
>running, except by Route Reflectors?? So what's "no
>synchronization" used for?
I don't understand what you are asking. Route reflectors run iBGP.
The purpose of no synchronization is principally to speed convergence
in non-transit AS. As others have been said, its importance is
vastly overstated.
>
>I have one more question: Is it true that routes injected into BGP
>within an AS carry a
>next hop attribute of the BGP router that first advertised the
>route? Please explain.
That's the usual behavior, although an alternate next hop can be set
when needed. For purposes of the CCIE, I wouldn't worry about that
case.
>
>Regards,
>Hunt Lee
>
>
>Howard C. Berkowitz wrote:
>
>> >No worries John. It was I who mentioned the devious nature of
>> >classless and synch as well :)
>>
>> Always remember that the best ISPs have no class.
>>
>> >
>> >Keep in mind that synch was designed for transit networks that have
>> >transit providing routers which do not run BGP. Back when the
>> >internet was smaller I expect some designs had the IGP in an AS
>> >carry the full table, or parts of it and hence it was relevant to
>> >make sure your BGP and IGP were synchronized to ensure you didn't
>> >blackhole routes.
>>
>> Precisely. I don't have the document number in front of me, but the
>> old RFC on BGP/OSPF interaction, which assumed this model, has been
>> recategorized as Historic (i.e., nobody does this, don't try it, it
>> was a blind alley)
>>
>> >Today, BGP is run fully meshed with all transit providing routers in
>> >an AS peering with IBGP and hence synch is a complete non issue.
>>
>> Full mesh, of course, has its scalability issues, and we deal with
>> iBGP scalability measures such as route reflectors. There is a trend
>> to have the main BGP at the edge, and to have principally an IGP in
>> the provider core. The core is stupid, and is traversed by MPLS
>> tunnels -- the role of the IGP is to establish reachability for these
>> LSPs, which run between BGP speakers on the edges.
_________________________________
FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html
Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
