topic Re: Double NAT in My Router

Double NAT

myrddin55 — Wed, 07 Jun 2023 09:52:10 GMT

Plusnet Hub 2 Router

I am trying to setup port forwarding rules for my Synology NAS. Synology has software that configures the router for me however it reports that it was prevented from accessing Upnp because there are 2 routers on my LAN. This is not correct.
from the cmd prompt >tracert 8.8.8.8 finds

two ip address in the private network range

192.168.0.0 (this is the hub2 router)

176.16.0.0 Unknown

a ping command to 176.16.0.0 fails - not detected

So how do I delete this IP addrress 176.16.0.0 as it does not show up on the IPV4 address table or any of the 3 ports. I'm confused, can anyone help me fix this please?

Re: Double NAT

dvorak — Wed, 07 Jun 2023 09:59:25 GMT

Moderators Note

This topic has been moved from Broadband to My Router

Re: Double NAT

bobpullen — Wed, 07 Jun 2023 10:12:11 GMT

@myrddin55 wrote:
So how do I delete this IP addrress 176.16.0.0 as it does not show up on the IPV4 address table or any of the 3 ports. I'm confused, can anyone help me fix this please?

You don't. Fairly certain that IP (should you have written 172.16.0.0?) is coming from the second hop that any outbound traffic will pass through. It belongs to a router out on the Plusnet/broadband network.

Can you provide the full output of the traceroute?

You probalby need to create the necessary port forwarding rule manually.

Edit: just spotted your file attachment, the IP does belong to external network kit as I've alluded to.

Re: Double NAT

myrddin55 — Wed, 07 Jun 2023 10:20:52 GMT

Good morning and thanks for getting back to me.

On my original post there is a .jpg file attachment with a screen shot of the tracert findings.

And yes i meant to use the generic IP address range 192 and 176

Cheers

Re: Double NAT

bobpullen — Wed, 07 Jun 2023 10:23:17 GMT

Thanks, definitely nothing you can do about that IP. There is one other potential option that would involve purchasing a static IP. Customers with static IP's do not visibly route through the 172 address. I personally think the manual port forwarding route would be more sensible though.

Re: Double NAT

myrddin55 — Wed, 07 Jun 2023 10:27:58 GMT

I'm trying not to purchase anything. Yesterday an SSL certificate from Fasthosts cost me £32 for a year as I cannot add a Lets Encrypt free one.

I digress

What about bridging?

Re: Double NAT

myrddin55 — Wed, 07 Jun 2023 10:33:29 GMT

Bob
Just to get my head around this, which will help with problem solving. Can you tell me where or what the 176 IP address point to and why it is detected by tracert but nothing else. Can it be masked, if yes this would be really helpful with the DSM/NAS

Thanks

Myrddin55

Re: Double NAT

MisterW — Wed, 07 Jun 2023 10:50:29 GMT

The 176 address is the gateway address into the Plusnet network. Its the first hop from your router to the internet. The router obtains the gateway address when it makes the PPPoE connection. In reality the NAS should not be seeing this as a router on your local network

Re: Double NAT

myrddin55 — Wed, 07 Jun 2023 10:58:00 GMT

This is useful. Thank you, I have some idea of what's going on now and possible solutions though there was no answer to my bridging mode enquiry?
I shall create my own port forwarding rules - I assume I can have more that one rule for the NAS as I understand it also need access to port 80.

I appreciate your help with this

Thank you (again)

Re: Double NAT

MisterW — Wed, 07 Jun 2023 11:11:50 GMT

though there was no answer to my bridging mode enquiry?

Not quite sure what you were asking ?

It's possible to set the Plusnet router into bridge mode, it then becomes just a modem. In this configuration your NAS would need to make the PPPoE connection and act as a router and would be allocated the public IP.

I'd be fairly sure that's not what you want...

Re: Double NAT

aesmith — Fri, 09 Jun 2023 08:06:28 GMT

That address 172.16.17.77 is a gateway so where in Plusnet's access network. It's just a hop that you pass through and its address is not significant. It is not related to NAT. None of your outbound or inbound Internet traffic is sourced from or destined to that address.

What address do you see if you go to ..

https://www.whatismyip.com/

Depending on your router should see that address assigned to PPPoE or WAN or something.