Can't Access Cable Modem Configuration While VPN is Active

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pcbored
DD-WRT Novice


Joined: 01 Jan 2019
Posts: 4

PostPosted: Fri Jun 28, 2019 20:05    Post subject: Can't Access Cable Modem Configuration While VPN is Active Reply with quote
I don't know if this has been an issue with anyone else or what I may be doing wrong, but ...

I have configured my Linksys WRT3200ACM with DD-WRT Firmware: DD-WRT v3.0-r39654 std (04/25/19). I have enjoyed internet access to any site ever since. I have been able to access my cable modem configuration page with no trouble.

Then I subscribed to a VPN provider. I can still access ALMOST any site with no issues. I can NO LONGER access my cable modem configuration page while the VPN service is active. There are also some web sites for which I get a connection time out error message when the VPN service is active. If I disable the VPN service, then once again everything is fine.

I get the following ping response to the cable modem from my internal network when The VPN service is inactive:

C:\>ping 192.168.100.1

Pinging 192.168.100.1 with 32 bytes of data:
Reply from 192.168.100.1: bytes=32 time=1ms TTL=63
Reply from 192.168.100.1: bytes=32 time=1ms TTL=63
Reply from 192.168.100.1: bytes=32 time=1ms TTL=63
Reply from 192.168.100.1: bytes=32 time=1ms TTL=63

Ping statistics for 192.168.100.1:
Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),
Approximate round trip times in milli-seconds:
Minimum = 1ms, Maximum = 1ms, Average = 1ms

That is the expected response. As I said, everything works correctly while the VPN service is disabled.

I get the following ping response to the cable modem from my internal network when The VPN service is active:

C:\>ping 192.168.100.1

Pinging 192.168.100.1 with 32 bytes of data:
Reply from 10.8.1.1: Destination port unreachable.
Reply from 10.8.1.1: Destination port unreachable.
Reply from 10.8.1.1: Destination port unreachable.
Reply from 10.8.1.1: Destination port unreachable.

Ping statistics for 192.168.100.1:
Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),

I have no idea where the 10.8.1.1 address comes from. That address is not in any configurations on my DD-WRT router. My internal network is on the 192.168.3.x network.

Where is this address coming from while the VPN is active? How can I re-establish connection to my cable modem web interface at 192.168.100.1 while the VPN is active?

Let me know if you need any additional information.
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pcbored
DD-WRT Novice


Joined: 01 Jan 2019
Posts: 4

PostPosted: Sun Jun 30, 2019 0:07    Post subject: Reply with quote
Thank you both for you help. The first suggestion worked well. I can now access the configuration page of my modem without disabling the VPN service. Still, though, there are some web sites I can not access without disabling the VPN.

On another note: where is the firewall script? I've seen it referred to frequently, and I have looked for it in the file system. But, I do not know what I am looking for. What is the name and path of the script? Is it accessible from the router configuration pages?

Also, what is the specific shell used in this embedded linux? I am familiar with sh, bash, ksh, etc. What is the specific name of the command shell on this platform. (I know "echo $SHELL" returns "/bin/sh". Is it the Bourne shell)? Is it ash? I want to research it to familiarize myself with what it can do and its limitations.
pcbored
DD-WRT Novice


Joined: 01 Jan 2019
Posts: 4

PostPosted: Sun Jun 30, 2019 22:54    Post subject: Reply with quote
Once again, thank you for your help. OK, now i know how to add things to the firewall and startup scripts. But does anyone know the full paths to the scripts? I guess I'm just very curious.

I apologize for asking such novice questions. I was a *nix admin for 20+ yrs. so I know it takes alot of research to learn a new system. Current documentation for DD-WRT is difficult to locate. I keep trying to extrapolate from the old documentation but not always successfully.

Anyway, thank you so much for your assistance.
pcbored
DD-WRT Novice


Joined: 01 Jan 2019
Posts: 4

PostPosted: Mon Jul 01, 2019 1:10    Post subject: Reply with quote
Thank you, eibgrad. This paradigm makes perfect sense. I feel enlightened.

This way, if one wants to make a change, it may be best to modify the /tmp/.rc* file(s) then run them to see the results before committing them to nvram. If there is a problem, just reboot.

Thanks again. Smile
Morphlingg
DD-WRT Novice


Joined: 17 Jul 2019
Posts: 4

PostPosted: Wed Jul 17, 2019 17:33    Post subject: Re: Can't Access Cable Modem Configuration While VPN is Acti Reply with quote
pcbored wrote:
I don't know if this has been an issue with anyone else or what I may be doing wrong, but ...

I have configured my Linksys WRT3200ACM with DD-WRT Firmware: DD-WRT v3.0-r39654 std (04/25/19). I have enjoyed internet access to any site ever since. I have been able to access my cable modem configuration page with no trouble.

Then I subscribed to a VPN provider. I can still access ALMOST any site with no issues. I can NO LONGER access my cable modem configuration page while the VPN service is active. There are also some web sites for which I get a connection time out error message when the VPN service is active. If I disable the VPN service, then once again everything is fine.

I get the following ping response to the cable modem from my internal network when The VPN service is inactive:

C:\>ping 192.168.100.1

Pinging 192.168.100.1 with 32 bytes of data:
Reply from 192.168.100.1: bytes=32 time=1ms TTL=63
Reply from 192.168.100.1: bytes=32 time=1ms TTL=63
Reply from 192.168.100.1: bytes=32 time=1ms TTL=63
Reply from 192.168.100.1: bytes=32 time=1ms TTL=63

Ping statistics for 192.168.100.1:
Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),
Approximate round trip times in milli-seconds:
Minimum = 1ms, Maximum = 1ms, Average = 1ms

That is the expected response. As I said, everything works correctly while the VPN service is disabled.

I get the following ping response to the cable modem from my internal network when The VPN service is active:

C:\>ping 192.168.100.1

Pinging 192.168.100.1 with 32 bytes of data:
Reply from 10.8.1.1: Destination port unreachable.
Reply from 10.8.1.1: Destination port unreachable.
Reply from 10.8.1.1: Destination port unreachable.
Reply from 10.8.1.1: Destination port unreachable.

Ping statistics for 192.168.100.1:
Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),

I have no idea where the 10.8.1.1 address comes from. That address is not in any configurations on my DD-WRT router. My internal network is on the 192.168.3.x network.

Where is this address coming from while the VPN is active? How can I re-establish connection to my cable modem web interface at 192.168.100.1 while the VPN is active?

Let me know if you need any additional information.

I have got the same thing. When i have changed VPN client
the problem has gone, because bad VPN does not provide you access throught many of blocks. Check Veepn.com if you are intrested. On my experience can tell you that you won't see error pages)
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