THE DISCUSSION
Inter VLAN Communication – Will this work?
August 13, 2017 9:18 pm by Admin
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:
- As a network engineer, it is absolutely critical to plan your network to ensure you do not have such oversights.
- 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.
- VLAN tagging happens only on TRUNK ports, not on ACCESS PORTS.
THE COMMENTS
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Thanks Imran, this was helpful especially the explanation of trunk function. My question is, even after assigning specific vlan to a host using different switches, the traffic will still not have vlan tagging? How will traffic flow outside an assigned vlan to another vlan?
Hi Ryan,
VLAN Tagging is a concept applicable to only the TRUNK links. In case the link between the two switches was TRUNK, then the communication would not have happened. But since its an access port, traffic moves out of one switch and goes into the other without any of the switch detecting any anomalies.
Hope this helps.
Switch to switch connected in trunk port mode – so it will ping
no it wil not ping because it is in different vlans
Hi chaps!
What happens if I do the tagging on the PC?
Cheers, Michael
Normally the 2 Diff Valn means Its not communicate na then how its ping sir can u expalin the concept