How to model VLAN interfaces

[antong]

On many platforms, one can add interfaces for specific tagged VLANs on a real interface. For example on Linux, if there are tagged VLANs 13 and 14 on eth0, I can make eth0.13 and eth0.14 and assign IP addresses for these. (On BSD, it could be igb0 and igb0_vlan13 and igb0_vlan14.)

Is the right way then to add all the physical interfaces as device interfaces and specify the tagged vlans (13 and 14) and perhaps an untagged vlan, and then in addition make virtual interfaces named like eth0.13 (mode access, untagged vlan 13)? Would this eth0.13 have eth0 as parent interface?

[ThomasADavis]

The way we are doing it (in yaml, which we feed into netbox), so we can use it in ansible. Yes, there is other data we pickup from the node like inventory of dimms, drives, gbics, motherboard, etc. etc. This is then combined into netbox so we can generate node configs

      - name: bond0
        type: Link Aggregation Group (LAG)
        mode: Tagged (All)
        mtu: 9216

      - name: ovirtmgmt
        mtu: 9000
        type: virtual
        parent: bond0
        mode: access
        untagged_vlan:
          name: ovirtmgmt
          site: crt
          vlan_group: omni
        address: 192.168.84.200/22
        tags:
          - primary
          - default

      - name: eno1
        type: 10GBASE-T (10GE)
        mtu: 9216
        lag: bond0
        remote:
          switch: sw-d8-r13-u37
          port: swp9
          lag: bond0
          cable:
            color: '0000ff' # blue
            type: cat6
      - name: eno2
        type: 10GBASE-T (10GE)
        mtu: 9216
        lag: bond0
        remote:
          switch: sw-d8-r13-u39
          port: swp9
          lag: bond0
          cable:
            color: '0000ff' # blue
            type: cat6

So that's two interfaces, bonded together. The bond is what we set as the 'trunk', and then we define virtual interfaces with the untagged vlan attribute for the vlan they are hooked to on the bond0, and also point the virtual interface parent to the bond0.

Yes, you can use named interfaces instead of bond0.50 for example.

so simply:

• create a trunk interface.
• add a virtual interface, mode = access, untagged_vlan = vlan, set parent to trunk.

[candlerb]

Is the right way then to add all the physical interfaces as device interfaces and specify the tagged vlans (13 and 14) and perhaps an untagged vlan, and then in addition make virtual interfaces named like eth0.13 (mode access, untagged vlan 13)? Would this eth0.13 have eth0 as parent interface?

Yes that's exactly right. Physical eth0, virtual eth0.13 with eth0 as parent.

[robertmain]

If I'm understanding this correctly that means that the correct way to do this for router on a stick (in my case) is to create each VLAN as a virtual interface with the physical interface as it's parent, then loop through those in the config template?

[candlerb]

Yes, that's how I'd do it if you are using subinterfaces. In Cisco-ese:

interface GigabitEthernet0
  no shutdown
interface GigabitEthernet0.100
  ip address 1.1.1.1 255.255.255.0
interface GigabitEthernet0.200
  ip address 2.2.2.2 255.255.255.0

Those sub-interfaces only exist within the context of the parent.

The other approach is with VLAN router interfaces:

interface GigabitEthernet0
  switchport mode trunk
  switchport trunk allowed vlan 100,200
interface Vlan100
  ip address 1.1.1.1 255.255.255.0
interface Vlan200
  ip address 2.2.2.2 255.255.255.0

In that case I'd create vlan100 and vlan200 as virtual interfaces, but without GigabitEthernet0 as parent (because a L3 switch allows the same VLAN to appear on multiple ports)

[robertmain]

Well this is for a router, so it's a little weird. I've created virtual sub-interfaces off my trunk port, then set the relevant VLAN as an untagged VLAN on that virtual interface. Does that look right to you?