I have an 8021q trunk link that permits 3 out of 20 VLAN's. The trunk port permits VLAN ID's 2,3,4, and uses native VLAN 25. The VLAN ID's in the local VTP domain are 5-25. There are no other VLAN's in the switched domain at the location in question. There are no other switchports in VLAN 25.
The trunk port is connected to a WAN service provider layer2 device, which is connected to a VPLS service. If the service provider sends a frame onto the trunk port tagged with VLAN ID 50, will my trunk port accept the frame and forward it "somewhere" or will it drop the frame? Note that VLAN 50 does not exist at the location in question, there are no ports in that VLAN. So the question I have is... How does the "switchport trunk allowed vlan" command affect forwarding from an inbound perspective? If "switchport trunk allowed vlan" doesn't prevent a VLAN tagged frame from being accepted into a network, is there any way to prevent a VLAN tagged frame from entering your network that shouldn't be? The reason I ask is because I have a situation where the trunkport is accepting the frame that I assume it shouldn't, forwarding into my network, and a loop ensues. That loop is a differnet issue all together I think. My main question is about the behavior of "switchport trunk allowed vlan" as it relates to inbound and outbound forwarding. I have no idea why VLAN's tagged with VLAN 50 are entering my network and getting forwarded around. I know those frames are entering my network at this location because I see the 8021q header in wireshark. Thanks, --NZR _______________________________________________ cisco-nsp mailing list [email protected] https://puck.nether.net/mailman/listinfo/cisco-nsp archive at http://puck.nether.net/pipermail/cisco-nsp/
