cancel
Showing results for 
Search instead for 
Did you mean: 

Double NAT

myrddin55
Hooked
Posts: 7
Registered: ‎11-04-2021

Double NAT

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?

10 REPLIES 10
dvorak
Moderator
Moderator
Posts: 29,702
Thanks: 6,589
Fixes: 1,485
Registered: ‎11-01-2008

Re: Double NAT


Moderators Note


This topic has been moved from Broadband to My Router

Customer / Moderator
If it helped click the thumb
If it fixed it click 'This fixed my problem'
bobpullen
Community Gaffer
Community Gaffer
Posts: 16,924
Thanks: 5,003
Fixes: 317
Registered: ‎04-04-2007

Re: Double NAT


@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.

Bob Pullen
Plusnet Product Team
If I've been helpful then please give thanks ⤵

myrddin55
Hooked
Posts: 7
Registered: ‎11-04-2021

Re: Double NAT

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

bobpullen
Community Gaffer
Community Gaffer
Posts: 16,924
Thanks: 5,003
Fixes: 317
Registered: ‎04-04-2007

Re: Double NAT

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.

Bob Pullen
Plusnet Product Team
If I've been helpful then please give thanks ⤵

myrddin55
Hooked
Posts: 7
Registered: ‎11-04-2021

Re: Double NAT

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?

myrddin55
Hooked
Posts: 7
Registered: ‎11-04-2021

Re: Double NAT

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

MisterW
Superuser
Superuser
Posts: 16,009
Thanks: 6,055
Fixes: 437
Registered: ‎30-07-2007

Re: Double NAT

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

Superusers are not staff, but they do have a direct line of communication into the business in order to raise issues, concerns and feedback from the community.

myrddin55
Hooked
Posts: 7
Registered: ‎11-04-2021

Re: Double NAT

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)

MisterW
Superuser
Superuser
Posts: 16,009
Thanks: 6,055
Fixes: 437
Registered: ‎30-07-2007

Re: Double NAT

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...

Superusers are not staff, but they do have a direct line of communication into the business in order to raise issues, concerns and feedback from the community.

aesmith
Pro
Posts: 634
Thanks: 53
Fixes: 4
Registered: ‎26-09-2015

Re: Double NAT

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.