Hers the topology.

  • L2 switch

  • L3 switch

  • Router

    There are 2 VLANs. One VLAN ends on the L3 switch 1 VLAN on the router.

Here is the question. Can i connect the L3 switch and the router with just 1 cable(can 1 cable carry both L3 and L2 traffic)? If i can what should be the protocol i should use ?

  • 1
    please provide small diagram. It will be helpful for everyone
    – infra
    Jun 18, 2019 at 10:17
  • and could please explain device modals
    – infra
    Jun 18, 2019 at 10:21
  • L3 and l2 switches are hp. Router is cisco
    – user19215
    Jun 18, 2019 at 10:21
  • Here is a simple diagram. I'm doing my best to explain with a diagram. 💻l2 switch --->💻l3 switch----> ROUTER all connected with one cable to the next device.
    – user19215
    Jun 18, 2019 at 10:25
  • if you can provide these details,it will be more easy to identify answer. do you need intervlan routing and what is a requirement for VLAN on Router.
    – infra
    Jun 18, 2019 at 10:28

1 Answer 1


Seems like you're overthinking...

Can i connect the l3 switch and the router with just 1 cable(can 1 cable carry both l3 and l2 traffic)?

Since L3 packets are transported using L2 frames: yes, that is normal usage. You'll need to route across the L3 switch between the router and the remote VLAN:

             V1             V2
  L2 switch------L3 switch------router

Of course, the router can't talk to VLAN1 directly, but that's not required for L3 connectivity. Make sure the router gets a routing table entry for VLAN1's subnet with the L3 switch as gateway. The L3 switch can probably use the router as default gateway.

If you do need VLAN1 over L2 you'll need to use a VLAN trunk between L3 switch and router, and add VLAN1 to that.

If i can what should be the protocol i should use ?

The most common protocol is IP (v4 or v6) over Ethernet.

  • Thank you. Thats what i was asking. So i need another cable(from the trunk port on l3 sw to the v1 interface on the router) am i right?
    – user19215
    Jun 18, 2019 at 12:21
  • 1
    You can pass any number of VLANs (well, up to 4094 with 802.1Q tags) on a single link configured as a trunk (identically on both ends). Of course, you can also run a dedicated link for the 2nd VLAN.
    – Zac67
    Jun 18, 2019 at 12:25

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