4500X dot1q subinterfaces

[jtrohm]

I have a unique situation where I am running multiple q-in-q metro networks and would like to do layer 3 VRFs in standalone tags WITHOUT creating a vlan on the switch.

What I'd like to do is something like the following:

interface ten 1/1/1

 description Metro Production Network

 no switchport

 ip address 10.1.1.1 255.255.255.0

!

interface ten 1/1/1.901

 description Metro Isolated Network

 ip vrf forwarding Isolated

 encapsulation dot1q 901

 ip address 192.168.1.1 255.255.255.0

The end game is to be able to backhaul public Internet and Lab networks in a routable way without wasting Vlan numbers or dealing with overlapping vlans between metro providers.

What I'm running into is that my 4500X doesn't seem to take a sub-interface number when I try to configure it. The command is there, but it fails. Example:

 MYSW1(config)#int tenGigabitEthernet 1/1/1.901
                    ^
 % Invalid input detected at '^' marker. 

Thoughts? 

[Richard Burts]

I believe that what you are attempting to do with sub interfaces is not supported on this platform. And I am not sure that I really understand what you are trying to accomplish with this. What would interface ten1/1/1 connect to? Your explanation seems to indicate that you do not want to create a vlan on the switch. But this

interface ten 1/1/1.901

 encapsulation dot1q 901

essentially creates vlan 901.

HTH

Rick

[jtrohm]

---

@Richard Burts wrote:

I believe that what you are attempting to do with sub interfaces is not supported on this platform. And I am not sure that I really understand what you are trying to accomplish with this. What would interface ten1/1/1 connect to? Your explanation seems to indicate that you do not want to create a vlan on the switch. But this

interface ten 1/1/1.901

 encapsulation dot1q 901

essentially creates vlan 901.

HTH

Rick

---

Thanks Rick. 

It's more a cleanliness thing. Creating a subinterface with a dot1q tag doesn't create a vlan on the switch. It only allows the switch's port to act as a client on an external tagged vlan. I suspect you are right about the non-supported nature of this, but I want someone with a cisco.com e-mail address to confirm that and also confirm that the help commands show subinterfaces as valid (which I am sure is just lazy programming) before I give up.

MYSW1(config)#int ten 2/1/29.?
  <0-4294967295>  TenGigabitEthernet interface number

MYSW1(config)#int ten 2/1/29.55
                   ^
% Invalid input detected at '^' marker.

I can accomplish the same thing with VLANs, but if I create overlapping VLAN numbers between metro carriers, it gets messy. 

[Reza Sharifi · Accepted solution]

Sub-interfaces are not supported on the 4500x.

https://community.cisco.com/t5/switching/subinterfaces-hardware-limitation-on-catalyst-4500-x/td-p/2679651

HTH