RT-AC66U Weird WAN IP Issue

[KevJames]

Hi,

Been using an RT-AC66U connected to a BT ECI VDSL modem without issues - BT Broadband here in the UK.
Today I upgraded the RT-AC66U firmware from 378.54_2 to 380.67
http://192.168.1.254/Advanced_FirmwareUpgrade_Content.asp
Now I get two WAN IP Address entries - one public and one private - I can't figure out why this has happened, and I cannot get rid of the second entry.

 

[Veky]

Go to WAN -> Internet Connection -> Special Requirement from ISP and check if "Enable VPN + DHCP Connection" is enabled or disabled. I've had this happen when it was enabled. It was enabled by default in some older firmware versions.

 

[KevJames]

Go to WAN -> Internet Connection -> Special Requirement from ISP and check if "Enable VPN + DHCP Connection" is enabled or disabled. I've had this happen when it was enabled. It was enabled by default in some older firmware versions.

Many thanks for the reply - yes "Enable VPN + DHCP Connection" was enabled. When I disabled it the second WAN entry was gone! I'd never even noticed that setting and would never have sussed this - so thanks again!

The other weird thing is the Gateway - should it not be the same as the WAN address - why a private address ??

Everything does work OK - but I'm curious.

With the old Merlin firmware all the addresses were as expected. BUT I caanot go back to that firmware - a message appears saying the old firmware is no lomger compatible ?????

 

[skeal]

Many thanks for the reply - yes "Enable VPN + DHCP Connection" was enabled. When I disabled it the second WAN entry was gone! I'd never even noticed that setting and would never have sussed this - so thanks again!

The other weird thing is the Gateway - should it not be the same as the WAN address - why a private address ??

Everything does work OK - but I'm curious.

With the old Merlin firmware all the addresses were as expected. BUT I caanot go back to that firmware - a message appears saying the old firmware is no lomger compatible ?????

Probably things would all straighten out for you if you called your ISP to bridge your modem, however, if the modem is bridged you will likely need a static IP. Sometimes this is a free option other times not so much. The private IP is probably coming from the next hop. A modem/router etc. It sort of sounds like you are in DMZ on the device between your router and your internet provider.

 

[KevJames]

Probably things would all straighten out for you if you called your ISP to bridge your modem, however, if the modem is bridged you will likely need a static IP. Sometimes this is a free option other times not so much. The private IP is probably coming from the next hop. A modem/router etc. It sort of sounds like you are in DMZ on the device between your router and your internet provider.

My VDSL2 modem, supplied by BT, is an ECI B-FOCuS V-2FUb/I Rev.B which acts purely as a bridge - it is designed to work with a router. My BT Broadband package uses Dynamic IP addressing.

Up until today, I had a working setup with no strange private addresses appearing in my router configuration.

This issue only started today, when I upgraded the firmware on my router from Version 378.54_2 to 380.67.

I had to change a setting that I never had to worry about before to remove the second (private) WAN IP address entry.

But I still get an erroneous (private) Gateway address of 172.16.14.134 being reported on the Internet Status page - although everything IS working correctly. That reported Gateway address remains the same even if disconnect and reconnect obtaining a new dynamic WAN IP address.

 

[skeal]

Try a trace route to a Google dns server and post the results please.

 

[KevJames]

Microsoft Windows [Version 10.0.14393]
(c) 2016 Microsoft Corporation. All rights reserved.

C:\WINDOWS\system32>tracert 8.8.8.8

Tracing route to google-public-dns-a.google.com [8.8.8.8]
over a maximum of 30 hops:

1 <1 ms <1 ms <1 ms RT-AC66U [192.168.1.254]
2 * * * Request timed out.
3 * * * Request timed out.
4 5 ms 5 ms 5 ms 31.55.185.180
5 5 ms 6 ms 5 ms core2-hu0-19-0-1.colindale.ukcore.bt.net [195.99.127.142]
6 7 ms 8 ms 7 ms peer1-hu0-1-0-6.slough.ukcore.bt.net [62.172.103.147]
7 6 ms 6 ms 6 ms peer5-te0-0-0-32.telehouse.ukcore.bt.net [195.99.126.77]
8 7 ms 6 ms 6 ms 108.170.246.129
9 9 ms 8 ms 8 ms 216.239.57.169
10 8 ms 7 ms 7 ms google-public-dns-a.google.com [8.8.8.8]

Trace complete.

C:\WINDOWS\system32>

 

[skeal]

Microsoft Windows [Version 10.0.14393]
(c) 2016 Microsoft Corporation. All rights reserved.

C:\WINDOWS\system32>tracert 8.8.8.8

Tracing route to google-public-dns-a.google.com [8.8.8.8]
over a maximum of 30 hops:

1 <1 ms <1 ms <1 ms RT-AC66U [192.168.1.254]
2 * * * Request timed out.
3 * * * Request timed out.
4 5 ms 5 ms 5 ms 31.55.185.180
5 5 ms 6 ms 5 ms core2-hu0-19-0-1.colindale.ukcore.bt.net [195.99.127.142]
6 7 ms 8 ms 7 ms peer1-hu0-1-0-6.slough.ukcore.bt.net [62.172.103.147]
7 6 ms 6 ms 6 ms peer5-te0-0-0-32.telehouse.ukcore.bt.net [195.99.126.77]
8 7 ms 6 ms 6 ms 108.170.246.129
9 9 ms 8 ms 8 ms 216.239.57.169
10 8 ms 7 ms 7 ms google-public-dns-a.google.com [8.8.8.8]

Trace complete.

C:\WINDOWS\system32>

In my traceroute my private gateway address is given 192.168.xx.1 as the first contact or hop. Something is not right with yours as the gateway listed is not on your private network. What happens if you change your gateway to 192.168.1.1? You should see this setting in your WAN settings. What do you have for a gateway in Lan DHCP settings as well. There should be no gateway set in Lan settings at all. If you have your router set to automatic ip then you will not see a gateway setting under the WAN settings. Make sure gateway info in LAN DHCP settings is blank.

 

[KevJames]

In my traceroute my private gateway address is given 192.168.xx.1 as the first contact or hop. Something is not right with yours as the gateway listed is not on your private network. What happens if you change your gateway to 192.168.1.1? You should see this setting in your WAN settings. What do you have for a gateway in Lan DHCP settings as well. There should be no gateway set in Lan settings at all. If you have your router set to automatic ip then you will not see a gateway setting under the WAN settings. Make sure gateway info in LAN DHCP settings is blank.

Default Gateway in LAN - DHCP Server - is not set on my router, and I cannot see any other setting for a Gateway Address. All I've done is set my router IP address as 192.168.1.254

 

[skeal]

Default Gateway in LAN - DHCP Server - is not set on my router, and I cannot see any other setting for a Gateway Address. All I've done is set my router IP address as 192.168.1.254

Can you please show me a screen shot of where you configured the ip address 192.168.1.254?

 

[skeal]

Can you still login to the modem/router from your ISP?

 

[skeal]

If you can please tell me how you do it.

 

[Veky]

It's a thing that BT does to save on equipment and IP addresses. If everything is working fine, I wouldn't worry about it.

 

[KevJames]

Can you please show me a screen shot of where you configured the ip address 192.168.1.254?

 

[KevJames]

Can you still login to the modem/router from your ISP?

You mean remote WAN access to the router - yes I can but only if I "Enable Web Access from WAN" in the Administration - System menu - which I don't!

 

[KevJames]

It's a thing that BT does to save on equipment and IP addresses. If everything is working fine, I wouldn't worry about it.

????

 

[skeal]

This is the lan ip the one you use to access your router from inside your lan. The global ip is in WAN settings. This really looks alot like a double nat. It may mean that your modem /router is not really bridged. Can you still login to the ISP modem/router i'm thinking 172.16.14.1.

 

[skeal]

you see if you get a login page for your vdsl modem/router then it still has a routable address and is technically not bridged and would shed some light on your issue.

I have a bridged fibre modem. You can't see it it is transparent the modem/router is now only a one port modem.

Only your number 1 port should work if its bridged the others will be useless.

 

[Veky]

????

Examples from BT forums:

https://community.bt.com/t5/BT-Infi...ult-Gateway-a-PRIVATE-IP-address/td-p/1578249
https://community.bt.com/t5/Connect...D8980-n600/m-p/1467202/highlight/true#M105860

There are many more threads where people mention 172.16.x.x gateway addresses with BT.

I don't think it's CGNAT and they even state they're not using it -> http://btsupport.custhelp.com/app/answers/detail/a_id/44044/c/6433

Check if https://www.whatismyip.net shows a proper public IP address and try to forward a port and then test with http://canyouseeme.org

If you're still not sure, contact BT.

 

[KevJames]

Examples from BT forums:

https://community.bt.com/t5/BT-Infi...ult-Gateway-a-PRIVATE-IP-address/td-p/1578249
https://community.bt.com/t5/Connect...D8980-n600/m-p/1467202/highlight/true#M105860

There are many more threads where people mention 172.16.x.x gateway addresses with BT.

I don't think it's CGNAT and they even state they're not using it -> http://btsupport.custhelp.com/app/answers/detail/a_id/44044/c/6433

Check if https://www.whatismyip.net shows a proper public IP address and try to forward a port and then test with http://canyouseeme.org

If you're still not sure, contact BT.

Thanks, I will let the matter rest, and thank you skeal for your help.

This is the best explanation I can find ...

https://community.bt.com/t5/Connect...g-IP-Address-gives-Request-Timed/td-p/1155630