Connection to MX to Cisco 2900

[Jai1]

Hopefully an easy one but I just cant get this to work.

We have a Cisco 2900 series router (ISP managed) to our MPLS.  They have configured a port on it as follows:

interface GigabitEthernet0/1
description Meraki VPN Link
no ip address
duplex auto
speed auto
!
interface GigabitEthernet0/1.5
encapsulation dot1Q 5
ip address 172.16.1.17 255.255.255.240
!

We are connecting to a LAN port on the MX since we dont want any NAT.

I have tried setting the MX Port up as Trunk, Native VLAN5 but traffic wont pass on it.  I also tried Access VLAN 5 on the MX but with no luck.

If i use the WAN port on the MX and set it as a VLAN 5, it works.

What am i missing when it is a LAN port?

[ww · Accepted solution]

Can you try

Trunk: Native 1, tagged 5

[cmr]

On the WAN port you can select no Nat (it is a checkbox towards the bottom) and tag as VLAN5

[PhilipDAth]

You must have an Internet connection connected to one of the two WAN ports on the MX.

You can configure the MPLS circuit off a LAN port using the settings mentioned by @ww , but that does not negate the requirement above.

You can configure the MPLS circuit on the WAN port if the Internet is available via that path.

You could also consider using NO-NAT as mentioned by @cmr , or putting the MX into passthrough mode so it does no routing (just acts like a switch).

https://documentation.meraki.com/MX/Networks_and_Routing/MX_Layer_2_Functionality#:~:text=When%20Pas... 

[Jai1]

Thank you so much, that was the issue!  i was just assuming it would want Native on VLAN 5 since thats what i wanted to use from the Cisco