Physical Interface with An IP Address And Subinterface Aith An IP Address living On The Same Interface

[beardalex]

I have a router that's using a physical interface gi0/0 with two IP addresses on it. One is the primary IP address and the other is a secondary. I've recently added a subinterface on this interface. If memory serves me correctly the physical interfaces should except all untagged traffic from a switch and the subinterface will, of course, accept traffic from the VLAN that's getting trunked from the switch. I've tested this is out in a virtual lab and it seems to work, however, I wanted to post this to validate my logic is correct. 

[Jon Marshall · Accepted solution]

You are correct although if memory serves me correctly I have found some devices and/or IOS versions do not like this but it was so long ago I could be wrong.

Sorry to be so vague but I can say I have definitely set it up the way you want before and it has worked.

Jon

[Masoud Pourshabanian]

Hello John and beardalex ,

Normally, it is the case except for those versions that Jon mentioned. You can change this behavior by playing with the native vlan though.

Masoud