Different vlans same subnet

Posted on 2014-03-18
Medium Priority
Last Modified: 2014-03-18
Hi all,

I have two devices both in the same subnet using two different Vlans, 10 on a Cisco and 110 on a Juniper.  Both in the same subnet.

If I setup a trunk should between the two, should I tag it with Vlan 10 and 110, or should I just tag the trunk on the Cisco side with vlan 10 and tag the Juniper side of the trunk with 110 ?  

Right now would be a great time for a nice little hardware lab.

Question by:rotarypwr

Assisted Solution

by:Tim Phillips
Tim Phillips earned 1000 total points
ID: 39937720
I don't think you want to use VLANs if you are going to use the same subnet and want them connected.  Rather, just connect the switches together with the same VLAN for the same subnet.  

Otherwise, use two different subnets, one for each VLAN, and trunk both VLANs up to a router to route between them for connectivity.
LVL 20

Accepted Solution

rauenpc earned 1000 total points
ID: 39938058
As you have it configured, using the same subnet with two different vlans, the only way to make them work together is to purposely "misconfigure" the link between the two. You would essentially make both links a trunk, and set the native or untagged vlan to 10 and 110 on the respective switches. This way the untagged frames will go to the same subnet, but in reality this is a misconfig situation.

The best way to handle this would be to use the same vlan numbers and subnets and avoid the mismatch, as coolrazor007 pointed out.

Author Closing Comment

ID: 39938591
Thanks.  I'm going to ask another question on this matter.   Appreciate the feedback!

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