Inter VLAN Communication

Will HOST A be able to communicate with HOST B? – Inter VLAN Communication

VLAN is locally significant to the switch. So when SWITCH A receives traffic from HOST A on a VLAN 10 port, its function is to ensure that traffic (or ARP broadcast) can only be sent through other VLAN 10 ports. So it forwards on the VLAN 10 access port which is connected to SWITCH B.

Remember – Traffic out of access port does not have VLAN Tagging! It goes out as normal traffic.

So when SWITCH B receives traffic from a VLAN 20 port, it ensures that it only forwards traffic on to other VLAN 20 access ports.

And hence the communication between HOST A and HOST B is a SUCCESS!

Learning from this:

  1. As a network engineer, it is absolutely critical to plan your network to ensure you do not have such oversights.
  2. A situation like this more common than you might think, where you are expecting traffic to be segregated by VLANs, but because of your oversight of not creating a TRUNK, traffic segregation does not happen.
  3. VLAN tagging happens only on TRUNK ports, not on ACCESS PORTS.