How Switchport Trunk work? I the scenario below; I can sniff the traffic between Win7 and UbuntuSrvr on **Line A** but this is cannot be done on **Line B** Note: ports are on trunk mode. Why this is happening?? ![enter image description here](

Assuming Win7 and ubuntuSrvr1 are using IPv4 in the network layer: Win7 initially ARPs Srvr1's IP address, making all switches in the L2 segment/broadcast domain/VLAN aware of its MAC address and port. When Srvr1 replies to that ARP request, all switches between them learn Srvr1's MAC address and port as well.

Any following unicast traffic then gets forwarded on the direct path between those hosts. Link B is not on that path, so you can't tap into their traffic there.

Whether or not VLANs and trunks are used doesn't matter as long as the two hosts are connected to the same VLAN.

If they weren't on the same VLAN but got routed on R1, traffic would cross neither A nor B.