Can access host from external networks... but only sometimes

putteb · 07-16-2008, 10:06 AM

Hi,

I hope someone can have a clue what my problem might be.

In my home i have a router directly connected to the wall and the router has a static external ip. From my computers that are connected to the router i can access the network via the external ip (ping it, access open ports...). So far everything good...

But when i'm in other networks i haven't been able to access the router via the external IP... most of the time. Sometimes during the day it works fine and i haven't changed anything in the meantime (i don't even have access to do that). I noticed the problem some days ago. I haven't had this problem before. Can anyone guess what's wrong? I have turned off any firewall or any other settings in the routher that can hinder access. It shouldn't be a configuration problem anyway.

Could it be activities from other people in some way? My ISP says it's not their problem but mine.

TIA,
Patrik

johnwill · 07-17-2008, 06:55 AM

Connected to the wall? What's behind the wall? We need to know what hardware supplies the Internet connection.

putteb · 07-17-2008, 07:01 AM

What's behind the wall is beyond my control and knowledge. That's my ISP. I want to make clear that i have no problems with my internet access. The only problem is to access my router and network from external networks.

Should i ask some questions to my ISP? What questions?

johnwill · 07-17-2008, 07:27 AM

Well, what's behind the wall is likely the source of your problem, which is why I ask.

Let's do a test.

Connect a computer directly to the wall outlet and post the following information.

Hold the Windows key and press R, then type CMD to open a command prompt:

In the command prompt window that opens, type type the following command:

Note that there is a space before the /ALL, but there is NOT a space after the / in the following command.

IPCONFIG /ALL

Right click in the command window and choose Select All, then hit Enter.
Paste the results in a message here.

If you are on a machine with no network connection, use a floppy, USB disk, or a CD-RW disk to transfer a text file with the information to allow pasting it here.

putteb · 07-17-2008, 09:03 AM

I replaced the wall connection so that my computer connects directly to the wall. Here's the output:

Code:

C:\Users\Patrik>ipconfig /all

Windows IP Configuration

   Host Name . . . . . . . . . . . . : Patrik-PC
   Primary Dns Suffix  . . . . . . . :
   Node Type . . . . . . . . . . . . : Hybrid
   IP Routing Enabled. . . . . . . . : No
   WINS Proxy Enabled. . . . . . . . : No

Ethernet adapter Local Area Connection 2:

   Media State . . . . . . . . . . . : Media disconnected
   Connection-specific DNS Suffix  . :
   Description . . . . . . . . . . . : WatchGuard Secure Client Virtual NDIS6 Adapter
   Physical Address. . . . . . . . . : 02-00-4E-43-50-49
   DHCP Enabled. . . . . . . . . . . : Yes
   Autoconfiguration Enabled . . . . : Yes

Ethernet adapter Local Area Connection:

   Connection-specific DNS Suffix  . :
   Description . . . . . . . . . . . : Marvell Yukon 88E8001/8003/8010 PCI Gigabit Ethernet Controller
   Physical Address. . . . . . . . . : 00-11-2F-87-0A-7A
   DHCP Enabled. . . . . . . . . . . : No
   Autoconfiguration Enabled . . . . : Yes
   IPv4 Address. . . . . . . . . . . : 193.11.235.17(Preferred)
   Subnet Mask . . . . . . . . . . . : 255.255.254.0
   Default Gateway . . . . . . . . . : 193.11.234.1
   DNS Servers . . . . . . . . . . . : 193.11.230.41
                                       83.140.87.2
   NetBIOS over Tcpip. . . . . . . . : Enabled

I configured my TCP/IPv4 settings according to what i've got from my ISP. What i have myself configured are the IPv4 address, subnet mask, default gateway, and dns servers. That is exactly what i set in my router too.

putteb · 07-17-2008, 09:22 AM

In case it's helpful, here's the output of ifconfig -a in ubuntu with the same ip configuration:

Code:

eth0      Link encap:Ethernet  HWaddr 00:11:2f:87:0a:7a  
          inet addr:193.11.235.17  Bcast:193.11.235.255  Mask:255.255.254.0
          inet6 addr: fe80::211:2fff:fe87:a7a/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:2889 errors:0 dropped:0 overruns:0 frame:0
          TX packets:524 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:1136675 (1.0 MB)  TX bytes:109484 (106.9 KB)
          Interrupt:17 

lo        Link encap:Local Loopback  
          inet addr:127.0.0.1  Mask:255.0.0.0
          inet6 addr: ::1/128 Scope:Host
          UP LOOPBACK RUNNING  MTU:16436  Metric:1
          RX packets:1443 errors:0 dropped:0 overruns:0 frame:0
          TX packets:1443 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0 
          RX bytes:78764 (76.9 KB)  TX bytes:78764 (76.9 KB)

djaburg · 07-17-2008, 12:36 PM

Are there specific things that you're trying to do remotely that require you to connect to your home network? I guess my first question would be what things are you trying to do, because it might be as simple as forwarding the correct port to the correct PC inside your network.

putteb · 07-17-2008, 01:01 PM

yeah, that's a good question. Unfortunately that's not where the problem is, since i have a good setup regarding port forwarding. I use it for many services so i need to forward several ports. The problem lies earlier, i.e. just to access the router and ping its external ip. I have port forwarding e.g. to the router admin page and for that it doesn't matter whether i have a computer connected to it at all.

cheers

johnwill · 07-18-2008, 11:04 AM

You have a router (NAT layer) between you and the ISP. That's going to prohibit any port forwarding if you can't change anything on that interface.

putteb · 07-18-2008, 11:53 AM

Do you mean that incoming traffic has no way to get through to my computer or router (whatever is connected directly to the outlet)? That has always been possible before and at the moment it is usually possible some times during the day.

Maybe one clue is that i have so far always been able to access it from my own network and also if i ssh into another computer at a different location, and also if I ssh into yet another location from that computer. As long as i start from my own network i can access it no matter how many tiers i ssh.

johnwill · 07-19-2008, 10:22 AM

You can get incoming traffic that you directly solicit, however something like a server where the connection is initiated remotely won't work without changing the settings on that remote router.

putteb · 07-20-2008, 02:01 AM

Thanks for your help! That would explain why it is possible to connect from a computer i have already ssh:ed into i guess?

But i'm still confused about that it works sometimes. E.g. I called a friend the other day and asked if he could ping me and it worked and i have never connected to him. Can it depend on the route his request takes? If the location just before it comes to me is one that i have connected to myself? Or must it be that the settings on the remote router varies?

I also wonder how you see that there is a router between me and my ISP from the output of ipconfig?

07-16-2008, 10:06 AM	#1 (permalink)
putteb Registered User Join Date: Jul 2008 Posts: 7 OS: Vista sp1, Ubuntu 8.04	Can access host from external networks... but only sometimes Hi, I hope someone can have a clue what my problem might be. In my home i have a router directly connected to the wall and the router has a static external ip. From my computers that are connected to the router i can access the network via the external ip (ping it, access open ports...). So far everything good... But when i'm in other networks i haven't been able to access the router via the external IP... most of the time. Sometimes during the day it works fine and i haven't changed anything in the meantime (i don't even have access to do that). I noticed the problem some days ago. I haven't had this problem before. Can anyone guess what's wrong? I have turned off any firewall or any other settings in the routher that can hinder access. It shouldn't be a configuration problem anyway. Could it be activities from other people in some way? My ISP says it's not their problem but mine. TIA, Patrik

07-17-2008, 06:55 AM	#2 (permalink)
johnwill Manager, Networking Forums Join Date: Sep 2002 Location: S.E. Pennsylvania, US Posts: 31,468 OS: XP-Pro, Vista, Linux Blog Entries: 1	Re: Can access host from external networks... but only sometimes Connected to the wall? What's behind the wall? We need to know what hardware supplies the Internet connection. __________________ If TSF has helped you, Tell us about it! or Donate to help keep the site up! Microsoft MVP - Windows Desktop Experience

07-17-2008, 07:01 AM	#3 (permalink)
putteb Registered User Join Date: Jul 2008 Posts: 7 OS: Vista sp1, Ubuntu 8.04	Re: Can access host from external networks... but only sometimes What's behind the wall is beyond my control and knowledge. That's my ISP. I want to make clear that i have no problems with my internet access. The only problem is to access my router and network from external networks. Should i ask some questions to my ISP? What questions?

07-17-2008, 07:27 AM	#4 (permalink)
johnwill Manager, Networking Forums Join Date: Sep 2002 Location: S.E. Pennsylvania, US Posts: 31,468 OS: XP-Pro, Vista, Linux Blog Entries: 1	Re: Can access host from external networks... but only sometimes Well, what's behind the wall is likely the source of your problem, which is why I ask. Let's do a test. Connect a computer directly to the wall outlet and post the following information. Hold the Windows key and press R, then type CMD to open a command prompt: In the command prompt window that opens, type type the following command: Note that there is a space before the /ALL, but there is NOT* a space after the / in the following command.* IPCONFIG /ALL Right click in the command window and choose Select All, then hit Enter. Paste the results in a message here. If you are on a machine with no network connection, use a floppy, USB disk, or a CD-RW disk to transfer a text file with the information to allow pasting it here. __________________ If TSF has helped you, Tell us about it! or Donate to help keep the site up! Microsoft MVP - Windows Desktop Experience

07-17-2008, 12:36 PM	#7 (permalink)
djaburg Registered User Join Date: May 2008 Posts: 333 OS: XP SP2	Re: Can access host from external networks... but only sometimes Are there specific things that you're trying to do remotely that require you to connect to your home network? I guess my first question would be what things are you trying to do, because it might be as simple as forwarding the correct port to the correct PC inside your network. __________________ Computers make it easier to do a lot of things, but most of the things they make it easier to do don't need to be done. Andy Rooney

07-17-2008, 01:01 PM	#8 (permalink)
putteb Registered User Join Date: Jul 2008 Posts: 7 OS: Vista sp1, Ubuntu 8.04	Re: Can access host from external networks... but only sometimes yeah, that's a good question. Unfortunately that's not where the problem is, since i have a good setup regarding port forwarding. I use it for many services so i need to forward several ports. The problem lies earlier, i.e. just to access the router and ping its external ip. I have port forwarding e.g. to the router admin page and for that it doesn't matter whether i have a computer connected to it at all. cheers

07-18-2008, 11:04 AM	#9 (permalink)
johnwill Manager, Networking Forums Join Date: Sep 2002 Location: S.E. Pennsylvania, US Posts: 31,468 OS: XP-Pro, Vista, Linux Blog Entries: 1	Re: Can access host from external networks... but only sometimes You have a router (NAT layer) between you and the ISP. That's going to prohibit any port forwarding if you can't change anything on that interface. __________________ If TSF has helped you, Tell us about it! or Donate to help keep the site up! Microsoft MVP - Windows Desktop Experience

07-18-2008, 11:53 AM	#10 (permalink)
putteb Registered User Join Date: Jul 2008 Posts: 7 OS: Vista sp1, Ubuntu 8.04	Re: Can access host from external networks... but only sometimes Do you mean that incoming traffic has no way to get through to my computer or router (whatever is connected directly to the outlet)? That has always been possible before and at the moment it is usually possible some times during the day. Maybe one clue is that i have so far always been able to access it from my own network and also if i ssh into another computer at a different location, and also if I ssh into yet another location from that computer. As long as i start from my own network i can access it no matter how many tiers i ssh.

07-19-2008, 10:22 AM	#11 (permalink)
johnwill Manager, Networking Forums Join Date: Sep 2002 Location: S.E. Pennsylvania, US Posts: 31,468 OS: XP-Pro, Vista, Linux Blog Entries: 1	Re: Can access host from external networks... but only sometimes You can get incoming traffic that you directly solicit, however something like a server where the connection is initiated remotely won't work without changing the settings on that remote router. __________________ If TSF has helped you, Tell us about it! or Donate to help keep the site up! Microsoft MVP - Windows Desktop Experience

07-20-2008, 02:01 AM	#12 (permalink)
putteb Registered User Join Date: Jul 2008 Posts: 7 OS: Vista sp1, Ubuntu 8.04	Re: Can access host from external networks... but only sometimes Thanks for your help! That would explain why it is possible to connect from a computer i have already ssh:ed into i guess? But i'm still confused about that it works sometimes. E.g. I called a friend the other day and asked if he could ping me and it worked and i have never connected to him. Can it depend on the route his request takes? If the location just before it comes to me is one that i have connected to myself? Or must it be that the settings on the remote router varies? I also wonder how you see that there is a router between me and my ISP from the output of ipconfig?