Let's assume we have 2 switches, switch A and Switch B. We interconnect both switches using FastEthernet0/1 interface on both of them. The fastethernet0/1 port on Switch A is configured as belonging to VLAN 24. Same interface on Switch B is configured as belonging to default VLAN (VLAN 1). For connecting both switches I use a cross-over cable, and I DON'T configure trunk on the link.
The question is: would the traffic sourced on a workstation connected to switch B (vlan 1 traffic) traverse the fastethernet0/1 port in Switch A and will it reach a workstation connected to any other port of Switch A?
I believe not, because there is a VLAN mismatch at the 2 inter-connecting ports.
Am I right?
Thanks in advance.
If interconnection between Switch A and Switch B is an access link (no trunking) belonging to vlan 25 on Switch A and vlan 50 on Switch B, the Ethernet continuity is OK, switches will forward frames without bothering about vlans.
Since L2 connectivity is OK, you can consider it is equivalent as having both PC on the same VLAN. in fact, the "VLAN" is the same from end to end, it is just numbered differently on the switches.
you will see there is a vlan mismatch when you do a show CDP nei on these ports. This is because CDP passes the vlan number and trys to help you out. but as stated before if the ports are not designated as trunks there is no tagging.
The concept of a Native VLAN only exists when there is a trunk. When there is no trunk, traffic between the two devices is not tagged, so the frames that move across the link are not tagged with any VLAN information. So even if the port on switch A belongs to VLAN x and the port on switch B belongs to VLAN y, if the link is not configured as a trunk, then VLAN x and VLAN y are effectively bridged.
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Both ports are configured as access port? If yes the frames are not tagged, and traffic can be exchanged between the two equipments. But only L2 traffic, L3 can also when the subnet is the same for the two vlans.
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