[ednog] Using MPLS to replace layer 2 trunking

Vincent Celindro vcelindro at northwestern.edu
Fri Jul 29 02:14:28 EDT 2005

Just looking for comments, maybe seeing if anyone else is doing this. We
have a couple of applications where it is a requirement to have devices
reside on the same layer2 network, but are located off different routers.
Essentially we would like vlan A to exist at both routing Sites 1&2.
Traditionally this is done by trunking Vlan-A across routing sites/core.

I would like to use MPLS specifically EoMPLS to achieve the same goal. I
would like to not have to trunk VlanA across the infrastructure and the
headaches associated with this, while gaining the other advantages
associated with MPLS. As I understand this I can actually have VlanA local
only to site1 create an EoMPLS tunnel and have all traffic exit at Site2 on
VlanA or any other Vlan, and have the 2 vlans be in one Layer2 domain. This
appears to be easily done, if I create the EoMPLS tunnel at both sites based
upon a physical port or a sub interfaced port ( per vlan EoMPLS). 

I'm guessing that most networks are like ours, where access layer switches
are trunked to some aggregate device or directly to a 6509. So port based
EoMPLS doesn't seem to be an option. I also don't think most of us use
subinterfaces to connect access layer switches, trunking seems to be the
standard. This also doesn't seem ideal, since you would have to have an
EoMPLS tunnel per subinterface for a vlan, so I may need 10 tunnels just for
trying to do this for a single vlan. 

So looking for ideas, I'd like to end up with a single EoMPLS tunnel per
vlan. The problem is how to force the traffic from Vlan-A into the tunnel?

                         _,--.   ___
         Site 1         .'    >-'  |           Site 2
       +--------+      |'          ....      +--------+
       |        |    ,''              ]|     | 6509   |
       | 6509   '''''' IP/MPLS CORE  \.------+ GIG/SFP|
       | GIG/SFP|     \..              \     |        |
       ++----+--+       |         .____'     +--+--`.-+
trunk .'      |trunk    |   _-|   \      trunk |     `.  trunk
     /        \         `---  `.__,|           /       `.
+--.'--+   +---+--+                        +--+----+   +-`.---+
+------+   +------+                        +-------+   +------+
 Vlan-A       Vlan-A                         Vlan-A     Vlan-A

    Access Layer switches                    Access Layer switches


Vincent Celindro
CCIE# 8630

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