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dot1Q inside a cable modem tagging vlan

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dkokoshi
dot1Q inside a cable modem tagging vlan

Hello,

Have anyone tested passing vlans inside a cable modem that is tagging another vlan. For example a CM is tagging vlan 100 and I want to pass vlan 50 inside it. Is there any configuration needed in the config file because it is not working?

Regards,
Dori

jeffs
I don't believe it will work

The MTU size is limited to 1518 or something like that...small enough to where QinQ won't work...only a single vlan tag will work I'm pretty sure.

mbernardi
It should be working. Check

It should be working. Check out Cable Labs L2VPN Spec. The CMTS must support 1522 byte packets on all L2VPN interfaces, and be able to transmit a 1526 byte packet out it's NSI. I just tried this a week or so ago and setup a sniffer between the CMTS NSI and uplink switch port and saw a proper QinQ packet via wireshark.

Do you have a config file working with a single tag(vlan 100 above)? What type of CMTS and CM are you using?

dkokoshi
Mbernardi thank you.

Mbernardi thank you.

I think it is a restriction in the CMTS side. I am using CASA C3200 cmts and CBN CH6541 cable modems.

Dori

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