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I have one switch that I want to use as an 802.1q tunnel, to make the spanning tree and etherchannel transparent, a pass through switch between a core switch and access closets, because I do not have enough phyiscal cabling to run to the core from each access.

So what is considers point-to-point?

I have one connection to the core, and on my dot1q tunnel switch each access switch has a separate connection, would the access switches be considered point-to-point to the core?

          CORE
            |          
       dot1qswitch
       /     |     \
 access1   acess2  access 3

After connections are made, i want etherchannel and cdp neighbors and spanning tree to see the core and the access switches as if they were cabled up directly port to port core to access.

Garry Baker
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  • Hi mate,

    Can you post some configs? Point-to-point it is a well known term used either in tunneling between two specific tunnel end points and also used by protocols like RSTP, underlining a connection between two RSTP participants (L2 bridges).

     – laf Aug 01 '13 at 05:26
  • point-to-point in this context should mean that behind switch port there is exactly 1 switch, which is not always true. Rapid convergence for example won't work if 1 port has >1 switch neighbors, because when one neighbor gives you permission to go into forwarding it reasonably expects you can, but if you have other neighbors behind same port, you obviously cannot. – ytti Aug 01 '13 at 06:44
  • @GarryBaker, you are hearing a lot about what you can't do... you can use QinQ w/ Layer2 Protocol Tunneling to emulate a point-to-point connection from an STP / VTP / CDP / LLDP perspective... see Layer2 Protocol Tunneling for Cat6500 – Mike Pennington Aug 01 '13 at 10:31
  • I deleted my answer since I was apparently out of my mind when I wrote it, but I'd like to ask you what the underlying reason is for wanting to get the aggregation switch out of the STP domain? – totallystubby Aug 01 '13 at 22:37
  • I asked the question because at the time I was confused on the idea of Point-to-Point concept with dot1q tunneling. But it actually makes sense to me now, that you have to have a p2p between the neighbors otherwise LACP/PAGP/UDLD would just get "multicast" to all the neighbors on my 'dot1qswitch' and they would all try to do LACP/PAGP/UDLD in a full mesh which is not way it works... There is more to the issue, but I did not want this to be a design question? But I need the 'dot1qswitch' to be transparent as there are other direct fiber connections from 'access' switches to the core. – Garry Baker Aug 02 '13 at 01:22
  • The answer is that is has to be "point-to-point" because these protocols have to agree on the parameters over the SP network via individual vlans over the core network to emulate a direct cable connection that has to exist for LACP/PAGP/UDLD to work, you would not do these protocols with a 'hub' in the middle with other switches to be able to intercept the "multicast" and try to create a full mesh – Garry Baker Aug 02 '13 at 01:25
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    What I need to do to solve this problem is have a 'dot1qswitch' at each location the core and access switches are separate by a distance but we do not have enough fiber to make all the connections. Creating a mini SP backbone and cable the core and access to individual Vlans to cross the mini SP backbone and terminate on ports that map to the SP vlans to make them point-to-point, utilizing the 1 fiber that I do have between the access and core buildings. – Garry Baker Aug 02 '13 at 01:29
  • @GarryBaker, please add the final solution as an answer and accept it... that way other people know how to solve this kind of problem. – Mike Pennington Aug 26 '13 at 06:54
  • Did any answer help you? if so, you should accept the answer so that the question doesn't keep popping up forever, looking for an answer. Alternatively, you could post and accept your own answer. – Ron Maupin Jan 04 '21 at 02:14

1 Answers1

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I created a QinQ tunnel over dot1q trunk between a 3750 switch stack at each location, with physical cat5 cables off the 6500 core switch to create point to point tunnels to do the PAgP to each access switch. This is working so far as a good work around for lack of cable infrastructure between the 2 buildings.

Garry Baker
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