11-12-2007 07:49 AM
Hi..
I have a doubt in AToM Pseudowire.. I ve got a AToM pseudowire setup between my two PE routers with lastmile being on Ethernet sub-interfaces with VLAN tag on both the ends. I want to confirm while the packet traverses from PE1 to PE2, the VLAN tag (4 Bytes) will be carried over the packet i.e ( 1500+18+VLAN tag+ VC label+Tunnel label) .... Or PE1 will strip the VLAN tag and send the rest i.e (1500+18+VC label+Tunnel label)...
Thanks in advance
11-12-2007 10:40 AM
Arun,
In this scenario, the vlan tag is indeed carried as part of the pseudowire payload.
Regards,
11-12-2007 10:57 AM
Arun, everything is transported with ATOM except Preamble, SFD, FCS.
Exlcuding these 3 everything from your SA/DA to your TPID (vlan info) is transported from Local to Remote PE.
Also the remote PE can overwrite the received Vlan info if configured to do so.
In your setup there shouldnt be any concern regarding the vlan tags.
HTH-Cheers,
Swaroop
11-12-2007 11:30 PM
In a pseudowire vlan is always carried forward from local PE to remote PE
The only issue to look at is that the interface over which the packet would get switched have the right mtu size
1500+18+VLAN tag+ VC label+Tunnel label+CW(optional)=1518+4+4+4+4(opt)=1534
or
for double-tag
1500+18+c-VLAN tag+s-VLAN tags + VC label+Tunnel label+CW(optional)= 1518+4+4+4+4+4(opt)= 1538
Hence, if you have not implemented MPLS TE
all interfaces should be able to pass 1500 MTU size payload with interfaces configured for 1542.
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