Basic question on Poin-to-Point Hardware (router vs switches)

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Oct 1st, 2010
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Folks, I know that if you setup a point-to-point circuit, I always have seen this deployed with routers on both ends.


Can you have such point-to-point circuit (circuit offered by a regular telco) but using layer 2 switches instead?

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Federico Coto F... Fri, 10/01/2010 - 15:10
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Hi,


Perhaps I'm not really understanding your question... but the only difference that I see is that the l2 switches will provide with you connectivity to the routers on both sides.


In other words, if you have a point-to-point connection between two routers it does not make any difference to have a l2 switch in front on both sides (since the switches are transparent at l3).


The problem is that if the connection is not Ethernet (but serial for example), you will require a serial port on a router.

But if the connection is Ethernet I don't see a problem.


Hope I'm making sense.


Federico.

news2010a Fri, 10/01/2010 - 15:40
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It is ethernet on both ends. Provider is offering EVPL.

Richard Burts Fri, 10/01/2010 - 15:43
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I do not want to be overly pedantic, but I believe that we must start by clarifying what is the real question and being careful about the terminology that we use.


One interpretation of point to point is that a layer 3 end device (router or switch) connects to some media and there is one and only one other layer 3 end device connected to that media. You certainly can achieve this using Ethernet technologies from a provider and could do it with router or layer 3 switch.


Another interpretation of point to point is typically associated with serial interfaces, especially if the serial interface uses HDLC or PPP encapsulation. In this interpretation there is no need for any protocol like ARP, since by definition there can be only 1 other layer 3 device connected to this media. In this interpretation the behavior is a bit different if you ping your own interface address and certain routing protocols (especially OSPF) treat the interface differently as they attempt to discover neighbors, etc. This interpretation can not be achieved on Ethernet interfaces.


So which interpratation of point to point did you intend?


HTH


Rick


[edit] I just re-read the original post and notice that it asks about using layer 2 switches. I do not see any way that you could achieve a functional point to point circuit using layer 2 switches. Layer 3 switches yes but layer 2 switches no.


Message was edited by: Richard Burts

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