Problems with Internet Connection Sharing (ICS), Windows Media Center, & Xbox 360 as Media Center Extender

Okay here is the problem. I have two networks connected to my Windows 7 Pro Media Center; one has internet (and is gigabit) the other doesn't (and is 100Based-T). I have a Media Center Extender and an Xbox 360 that I use as another Extender.

All works well until I try to share my internet connection between the two networks using Internet Connection Sharing. After enabling sharing the Xbox 360 can no longer find the Media Center no matter what I do. Disable ICS and everything is great again. Is there a work around to this? I need to share the internet with the other network, but I also need to have the 360 be able to connect.

I tried bridging the networks, but that only works until the next reboot and then the bridged connection has to be repaired for things to start working again.

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I assume that you've enabled Internet Connection Sharing on the gigabit Internet connection.  That automatically assigns an IP address of 192.168.137.1 to the Windows 7 Media Center's 100Base-T network connection and enables a DHCP server for the other devices on the 100Base-T network. 

Configure the Xbox 360 to obtain an IP address automatically, or assign it a static IP address in the 192.168.137.x range.


Boulder Computer Maven
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Steve Winograd

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Thanks for the reply. I should have provided a bit more information on the network setup before. The gigabit network is my main network. Here you go:

Network 1 (gigabit)

Cable Modem > Router > Switch

Network 1 has a couple laptops that connect to it wirelessly via the router, it also has a Mac mini, a Media Center Extender, the Xbox 360 and the Windows 7 Pro Media Center that are connected to the switch. This network has internet via the cable modem. DHCP is provided by the router. This is the problem network once ICS is enabled. After doing so the 360 can no longer find the  Media Center computer anymore even though they all still have IP addresses (looking at DHCP table on router). Xbox can still access internet as can all other devices on network regardless of whether ICS is enabled or not.

 

Network 2 (100Based-T)

This network basically consists of a router that connects to the media center and another (different) xbox 360. After ICS is enabled on the gigabit network (Network 1) the 360 can access the internet.

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When you enable ICS on Network 1, Windows 7 assumes that the computer connects directly to the Internet through that network.  If the computer uses the Windows Firewall, that might cause it to increase the security settings to protect against possible Internet-based attacks.  You might have to create exceptions in the Windows Firewall to allow the 360 to access the computer.   Check the Network and Sharing Center to see whether Windows 7 considers that connection to be Home or Public, then look at the corresponding profile in the firewall.  I'm sorry, but I don't know the details of how to configure the firewall.


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Steve Winograd

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I don't know if it is still the same in Windows 7 but doesn't ICS automatically change the sharing computer's IP to 192.168.0.1? That wasn't alterable IIRC and a lot of routers also use the same address for their default network address. That could cause network addressing, DNS server and DHCP server conflicts once ICS is enabled. Each router's address would need to be unique within the same subnet, with most devices set to use the gigabit router's address (or cable modem if pass-through) for DNS and for the LAN's DHCP server (excluding 192.168.0.1, 192.168.137.1 from the DHCP range). Possibly the ICS client(s) should be set to use a unique fixed address(es) within the same subnet. The 360 is apparently able to access DNS but is the DNS server it is using router 1, router 2, or the ICS computer (or direct from the ISP's DNS servers)?

Another thing that typically blocked ICS from working was the free versions of most third-party firewalls. I've also had subscription type firewalls start to block some network (nebios/broadcast?) functions as well once the "updates" subscription or trial use period lapsed (affected my WiFi connections). Some anti-malware software may also act like a firewall and can block certain network traffic (blocked remote desktop connections for example).

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In Windows 7, ICS sets the sharing computer's IP address to 192.168.137.1.  That avoids the router conflicts that you mention.
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For my own information, since the ICS computer must have 2 network adapters, how does the inbound adapter (from the router/modem) get its IP address after ICS is enabled. Does it continue to use the same DHCP address from the router? (last time I ever used ICS I had either a dial-up or internal ADSL modem in the ICS computer)

I'm trying to imagine the OP's LAN topology...no idea what his purpose is but... wondering why all devices aren't being connected through the same gigabit router? Looking in Windows Help for tips about this sort of network configuration and it basically says, don't do it. :-)

"Don't use ICS on a network with domain controllers, DNS servers, gateways, or DHCP servers. And don't use ICS on systems configured for static IP addresses."

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ICS has no effect on the TCP/IP settings of the inbound adapter (the one that you're sharing). 

When you enable ICS, it makes these changes on the host computer's outbound adapter:

  • Assigns a staic IP address (192.168.137.1 in Windows 7, 192.168.0.1 in earlier versions).
  • Runs a DHCP server.

That's why ICS warns you not to use it with a domain, DHCP, static IP, etc -- to avoid conflicts with existing network settings.


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Steve Winograd

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Thanks for the information everyone. What would be great is a solution though. Is there a way to share the internet connection between two different networks as they are described above? As I mentioned before, bridging them works until the next reboot, after which it needs to be "fixed" by windows 7.

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I would be very interested to hear if you have found a solution to this.  I have the same problem, but on a much simpler topology.

Internet -> Cable Modem -> Wireless Router (192.168.1.1, running DHCP)

XBox 360 is wired to the Wireless Router (gets ip 192.168.1.100, gw 192.168.1.1, snm 255.255.255.0)

Windows has two adapters (let's call them eth0 and eth1).  eth0 is connected wirelessly to the Wireless Router (gets ip 192.168.1.101, gw 192.168.1.1, snm 255.255.255.0).

In this setup (with eth1 disabled) everything works fine.  The XBox can connect to Media Center as an Extender, and stream video (everyone is happy).

Now enable ICS on eth0, sharing it with eth1.  Connected to eth1 is a hub, with (at the moment) only one other device attached (an OC phone).  The OC phone works great, Windows can still connect to the internet and can still see the Xbox.

The Xbox however cannot connect to Media Center.  It also fails the PC connection test.

Shouldn't this Just Work?

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Hi Douglas,

You may have already tried this, but running ICS and the second router is likely causing a conflict.

ICS provides DHCP on that eth1 adapter, and the router is probably running DHCP as well.

I suggest disabling the second (eth1) routers DHCP service to see if the issue resolves.


Chris
Microsoft Answers Support Engineer
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Last updated February 12, 2021 Views 7,774 Applies to: