From: Tshon (tshon@xxxxxxxxxxx)
Date: Wed Mar 13 2002 - 03:27:47 GMT-3
I agree with Manny,
I think you guys missed what Sync is for.
Manny Gonzalez wrote:
>Have we all forgotten the reason for Sync? If the path through the IGP
>is via any NON iBGP speakers, you run the risk of black holing traffic.
>This is the reason for Sync in the first place.
>
>(AS1)---(AS2_BGP_R1--iBGP_R2--OSPF_R3--OSPF_R4--iBGP_R5)---(AS10)
>
>Now, you know you can do a iBGP peering session between R1 and R2 and
>R5. If you are ISP_AS2 and someone chooses your PATH as a transit path,
>if the OSPF routers do not have those routes to the end AS's, guess
>what? bit bucket. So then BGP needs to make sure the IGP has the routes.
>
>If you turn off sync in the above scenario, what happens? You then
>better make sure that you turn on BGP on those OSPF routers as well.
>Otherwise, all the BGP speakers should have direct connectivity to
>assure path completeness.
>
>If somehow my view is flawed, I welcome the corrections :-))
>
>P.S. I believe IS-IS is able to handle a very large set of Internet
>routes. I also believe there is a very large backbone carrier using
>IS-IS to IGP portions of their backbone. But, these are uncorroborated
>reports.
>
>P.P.S. I assume Cisco couldn't care less what the best practice is in a
>Lab environment. If you think that route reflectors and confederations
>with 4 routers is insane, welcome to the CCIE Lab world.
>
>Regards,
>
>Manny
>
>Peter van Oene wrote:
>
>>It isn't actually possible to synchronize, nor do any transit providers. I
>>expect it's been universally disabled since 93-94 area.
>>
>>At 06:17 PM 3/12/2002 -0600, MADMAN wrote:
>>
>>> Is it even any longer possible to synchronize, I don't think any IGP
>>>could handle the injection of 100K+ routes!! Seems like outdated
>>>attribute of BGP and should just as well be disabled by default.
>>>
>>> Dave
>>>
>>>Peter van Oene wrote:
>>>
>>>>It is always wise to keep in mind the reasons various options exist in the
>>>>first place. IE, what problems where the designers trying to solve. Route
>>>>Reflection deals with peering in a topology that is fully meshed from an
>>>>IBGP perspective. Synchronization deals with route advertisement in a
>>>>topology that does not have a full IBGP mesh. Hence, these options are
>>>>designed for different networks and not likely to work well
>>>>together. Further, they shouldn't work together nor is there any sound
>>>>reason to try and make them work together.
>>>>
>>>>At 01:15 AM 3/13/2002 +0800, kenairs wrote:
>>>>
>>>>>Hi ,
>>>>>So in others words, aparting from redistribute into IGP , RR will only
>>>>>
>>>works
>>>
>>>>>if you have turn off syn.
>>>>>Am i correct ?
>>>>>
>>>>>Or is there any other way beside redistributing to IGP ?
>>>>>
>>>>>----- Original Message -----
>>>>>From: Sandro Ciffali <sandyccie@yahoo.com>
>>>>>To: kenairs <kenairs@hotmail.com>
>>>>>Cc: <ccielab@groupstudy.com>
>>>>>Sent: Wednesday, March 13, 2002 12:38 AM
>>>>>Subject: Re: BGP RR
>>>>>
>>>>>
>>>>>>Since you have sync on, Network advertize by R2 on bgp
>>>>>>will go into R1's routing table only if it is recd.
>>>>>>both on BGP and IGP, Only then R1 will advertize that
>>>>>>network to R3.
>>>>>>If you turn off the sync on R1 then you will see it
>>>>>>being advertized to R3.
>>>>>>Or else redistribute the ethernet on R2 into your
>>>>>>igrp.
>>>>>>
>>>>>>Sandro
>>>>>>--- kenairs <kenairs@hotmail.com> wrote:
>>>>>>
>>>>>>>Hi ,
>>>>>>>From the Cisco CD , is states the below
>>>>>>>
>>>>>>>When the route reflector receives an advertised
>>>>>>>route, depending on the
>>>>>>>neighbor, it does the following:
>>>>>>>
>>>>>>>
>>>>>>> a.. A route from an external BGP speaker is
>>>>>>>advertised to all clients and
>>>>>>>nonclient peers.
>>>>>>>
>>>>>>>
>>>>>>> b.. A route from a nonclient peer is advertised to
>>>>>>>all clients.
>>>>>>>
>>>>>>>
>>>>>>> c.. A route from a client is advertised to all
>>>>>>>clients and nonclient peers.
>>>>>>>Hence, the clients need not be fully meshed.
>>>>>>>Here is my topology,
>>>>>>>
>>>>>>> R1
>>>>>>> | |
>>>>>>> | |
>>>>>>> | |
>>>>>>> R2 R3
>>>>>>>
>>>>>>>All routers are able to reach each other through IGP
>>>>>>>( eigrp ) . R1 is the RR
>>>>>>>R2 and R3 is the client.
>>>>>>>
>>>>>>>Now, R2 has a E0 . It then have a network command
>>>>>>>under BGP and is propagrate
>>>>>>>to R1.
>>>>>>>But R1 does not advertised the route to R3 ..
>>>>>>>Why is this so ?
>>>>>>>All routers are syn enabled.
>>>>>>>
>>>>>>>
>>>>>>> but is R2 received a route from another AS, the
>>>>>>>route will be advertised to
>>>>>>>R3.
>>>>>>>
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