Santosh,

Let me jump in here since I think I know where the confusion lies.

  - As far as the P routers are concerned, all they see is an
    MPLS Label Switched Path (LSP) between the PE routers.

  - Section 4.2.7.3 in RFC 4577 does a pretty good job of
    explaining OSPF operation in this context. Please re-read
    this section and feel free to ask questions.

Hope this helps,
Acee

On Mar 20, 2007, at 7:28 AM, Santosh P K wrote:

Hi Padma,
     When you said its a "logical construct like VL and it is always
a p2p" you mean the underlaying link is always P2P link?  If it is an
P2P link then PE's should be connected directly not by inbetween P
routers right ?
I am getting confused with this P2P link. Can you please explain this?


On 3/20/07, Padma Pillay-Esnault <[EMAIL PROTECTED]> wrote:
Abhay D.S wrote:
> Yes forwarded by routers.
>
> Well, about the demand circuit part I suggest you dont follow the RFC, > since it may or may not be treated as DEMAND circuit.(It is a requirement > of the network to treat it as demand circuit, for example if you have
> heavy load
> of traffic on sham link then you can treat it as DC(demand circuit).
>
> If you really want to use sham link optimally, you can just increase
> the hello timeout
> on the sham links to be large and then let it be a proper p2p link. It
> is similar to hello
> suppression..
>
> --Abhay
>
> Santosh P K wrote:
>> Hi Abhay,
>>
>>     Thanks. Are OSPF control packts just forwarded by P routers on
>> sham link ? RFC 4577 says that Sham link is treated as OSPF demand >> circuit. In case of broad cast or NBMA configured as demand circuit >> hello are not supressed as per RFC 1793 section 3.2. that means hello >> are also forwarded to the endpoint just as OSPF control packets by P
>> router on sham link?
Sham link is a logical construct like VL and it is always a p2p.

Thanks

Padma
>>
>> Thanks and regards
>> Santosh P K
>>
>>
>> On 3/20/07, Abhay D.S <[EMAIL PROTECTED]> wrote:
>>> It is a SHAM...:-).
>>>
>>> Only sham link end point needs to be enabled in OSPF and reachable over
>>> the multi hop
>>> network by BGP or static means.
>>>
>>> Means Sham Link end points must be routable over the network for it to
>>> become UP.
>>>
>>> Santosh P K wrote:
>>> > Hi All,
>>> > I have some doubts on sham link. If a sham link is configured >>> > between two PE's which are connected by many P routers in IP backbone
>>> > , then is it nessary for all the P routes to run OSPF.
>>> > As per cisco user guid it is mentioned that
>>> > sham link is treated as virtual link. In case of virtual link
>>> > inbetween routers need to know OSPF protocol.
>>> >
>>> >
>>> > Thanks and regards
>>> > Santosh P K
>>> >
>>> > _______________________________________________
>>> > OSPF mailing list
>>> > [email protected]
>>> > https://www1.ietf.org/mailman/listinfo/ospf
>>> >
>>> >
>>>
>>>
>>
>> _______________________________________________
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>> https://www1.ietf.org/mailman/listinfo/ospf
>>
>>
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