I'm not questioning your design. When I ask a question is for a reason. I asked before if you were trunking the interface and you said no. About 5 responses later, it comes to light that you are trunking. That was a time wasted for you and for me.
Again, I asked you if you were pruning the Vlans and you said you are only sending Vlan 1 towards the ISP. The portion of the config above clearly indicates that you aren't pruning and all the Vlans are being forwarded to the HP switch. You don't want that as it can create problems. You have no control on the HP side so you want to limit what is sent to the ISP. They told only Vlan 1 is the transport Vlan, then you only send that Vlan and prune the rest.
You should have asked those questions before. I can't tell the level of knowledge from a poster unless the poster ask for more clarification.
The problem indicates there is a Vlan leakage from the HP to the 3750 within the ISP and it's passing Vlan 34 for some odd reason. You can control this behavior by pruning your Vlans per Victor's command.
Let us know how it works out.
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Edison.
