IP Passthrough Mode

PeterUK

Wondering how many people use this mode and have problems when your IP changes have made a case #463401 which is being looked at

I have the FWA-510

Zyxel_Kay

Hi @PeterUK

After reviewing your case #463401 and conducting further investigation, the behavior you're describing is actually expected when using IP Passthrough Mode.

In this mode, the FWA510 passes the IP address to the end device via DHCP. Typically, the end device retains the assigned IP address until the DHCP lease expires, even if the gateway becomes unreachable. This is common for many network devices, which hold onto the existing IP until the lease period ends. The decision to release or renew the IP address is usually handled by the end device, not the FWA510.

If your VPN drops due to an IP change, we recommend requesting a static IP from your ISP. This can help prevent disconnections caused by dynamic IP changes during VPN sessions.

PeterUK

Hi Kay

You might think its expected does not make it right and will note it in my review as said my Nighthawk M2 Mobile Router has its own solution by doing a 2 minute lease time which you can at least do.

It is not a hard thing to fix so I expect a solution in the coming months

And you saying “The decision to release or renew the IP address is usually handled by the end device, not the FWA510” is wrong in this case because how the FWA510 works in IP Passthrough Mode is not a bridge it is a client and server the FWA510 is a DHCP client so it is responsible for the IP it gets and how the DHCP server by FWA510 give that IP to the end device.

As said in case #463401 I have given two ways that this can be solved

Thanks

PeterUK

How I would solve it

Zyxel_Kay

Hi @PeterUK

When a device (STA) receives an IP address via DHCP, it is granted a lease time during which it can use that IP. Before this lease expires, the device is expected to send a DHCP renewal request to extend the lease. If the renewal does not happen, the lease expires, and the IP address may be reclaimed by the DHCP server.

In IP Passthrough mode, the mobile router acts as a bridge, passing the public IP directly to the STA. This means that the STA must handle its DHCP lease renewals independently, as the router does not manage the lease. Therefore, if the STA does not automatically renew the lease before it expires, it could lead to a loss of connectivity, such as the VPN disconnections that you mentioned. This behavior is dependent on the STA and not controlled by the router due to the bridging nature of IP Passthrough mode.

PeterUK

Unfortunately this is not true please recheck in how IP Passthrough Mode works Kay there is no bridge where the device DHCP directly to the ISP DHCP server as you can see here with the MAC

I have a NETGEAR Nighthawk M2 Mobile Router in IP Passthrough and the lease time is 2 minutes and you can see the source MAC is NETGEAR not the ISP router

With FWA510 its the same story in IP Passthrough only you give out a lease time of 1 hour by source MAC Zyxel not the ISP router

So at the very least I would like the lease to 2 minutes or a real fix like I said thanks

Zyxel_Kay

Hi @PeterUK

Thank you for your insights regarding the IP Passthrough Mode on the FWA510. We understand your concerns about the DHCP lease time and its impact on your connectivity.

Currently, there isn’t a way to modify the DHCP lease time for passthrough devices. However, we appreciate your suggestion, and I'd like to help you create an idea post on our Community to raise a feature request for this functionality. This way, we can gather support from other users and highlight its importance.

Here the idea post:

https://community.zyxel.com/en/discussion/26651/dhcp-lease-time-adjustment-for-nebula-mobile-router

If anyone have the similar request, please feel free to leave a comment or click vote. The votes and comments will be part of our evaluation process.