How to configure an ISP with a gateway on a different subnet?

Showing results for 
Show  only  | Search instead for 
Did you mean: 

How to configure an ISP with a gateway on a different subnet?

L0 Member

I got myself a weird one, for me at least. Got a remote office I'm not much involved with that got a new internet line and I'm supposed to configure it, but the info I got is just this:


Client IP: / subnet mask

        / subnet mask



(IPs are obviously fake, but the difference between them, their subnets and positions inside them are correct and all)


And that's it. No DHCP enabled, ISP router is a Microtik with 4x 10Gb ports that we have no access to. No additional info has been provided, local colleague tried asking for more info but they said basically "that's it, good luck"

I'm not a huge expert but I did configure quite a good number of internet lines around and I never ever seen anything like that, with the gateway outside of the subnet of the IPs. Not much hope in contacting their assistance because they don't speak any language I know.


Any idea on how should I configure the interface/virtual router/nat rules for this ... thing?

I am sure it's something simple and dumb to configure and I'm just missing it but I'm swamped and confused.


Cyber Elite
Cyber Elite

Hi @thebard ,


The solution to this puzzle is not simple and dumb.  However, I believe this is your solution:


  1. Create a default route to
  2. Create a route to pointing to your interface only.  The NGFW will consider it connected and ARP for the MAC address.
  3. If that does not work, verify their configuration with a laptop configured with your parameters above since a laptop allows a default gateway to be assigned to the interface.  If the laptop does not work, the ISP is jacked.




Help the community: Like helpful comments and mark solutions.
  • 1 replies
Like what you see?

Show your appreciation!

Click Like if a post is helpful to you or if you just want to show your support.

Click Accept as Solution to acknowledge that the answer to your question has been provided.

The button appears next to the replies on topics you’ve started. The member who gave the solution and all future visitors to this topic will appreciate it!

These simple actions take just seconds of your time, but go a long way in showing appreciation for community members and the LIVEcommunity as a whole!

The LIVEcommunity thanks you for your participation!