Mountain Lion cannot see any Windows PC on network

I manage the computers in a small office and we have a handful of Macs and a few Windows PCs (Windows 7). We use a Windows server (Home 2011) for backing up important data.

Last week two of the Macs were not longer able to connect to the shared folders on the server. As I delved deeper into this issue I discovered a few things:

• Both Macs are running Mountain Lion 10.8 and were recently updated.
• The ML Macs cannot ping, connect for sharing (Finder), or remote desktop into the Windows server
• In fact, I can't see any Windows computer in Finder on those two Macs and I can't ping any Windows computers on the network.
• The other Macs are running Lion 10.7 and have no problem seeing the Windows server in RDC, Finder, or ping.
• I can ping the ML Macs from the server. The Macs aren't set up for sharing or remote desktop so I did not try that.

Because the server can see the Macs but the Macs can't see the server, I am fairly certain that this is an issue on the two Macs and the recent update. I have seen various posts online about Samba problems in ML and workgroups. I have checked and, unless something has changed, the Macs are in the right workgroup in WINS in system preferences. Not being in the same workgroup would not prevent pinging an IP though. The inability of the Macs to even ping the Windows server is the most bothersome part of this to me.

This is a very serious issue because every day these two computers can't connect to backup on the server we risk losing weeks worth of work if a harddrive fails.

Is there anything I might have missed in my diagnosis?

Is the OSX firewall turned on? "System Preferences, Security and Privacy, Firewall" is where you find it. It may be blocking the communications from the Macs. Just a long shot guess on my part.

I forgot to mention that. The firewalls are not on. The Macs can't even ping the server. It is as if they aren't even there. At the same time, the server can ping the two Macs.

Do the ML Macs see each other? Can they see the Lion Macs? Can the Lion Macs see the ML ones?

Both of the ML Macs have not been sharing files but after I turned it on they can see all the Macs on the network.

Let's go more basic.
Tell us about your local network. One router? any switches? Tell us the IP addresses of the computers we're talking about (pingable, not pingable). Which ones are using WiFi and which are ethernet? Do all computers use DHCP to get IP address?
Have you gone into the router's admin web page and are all computers showing up?
Are you using WPA encryption? Does your router allow "guest" connections?
and etc, etc.

There is a Linksys wireless router at 192.168.1.1 which is plugged into an outlet that links to the Comcast fiber-optic router at 10.1.10.1. The server is plugged into the wireless router via ethernet cable and has an IP of 192.168.1.53.

The wireless uses WPA2 and does not allow guests.

All of the computers should be using DHCP. I did not set up this network but inherited it from the person who set it all up. He left a few weeks after I was hired and I have sent him an email about admin passwords for the routers. I was able to get into the wireless router's admin page. The computers with a 192.168.1.* IP show up on the list of connected devices.

The ML Macs get a 10.1.10.* IP on both the wireless and the wired connections.

The Lion Macs in the office get a 10.1.10.* IP when connected to the LAN but on the wireless they have a 192.168.1.* IP. When I disconnected the wireless on the Lion Mac, I was not able to connect to the server.

There are 4 Windows computers in the office and as far as I know they are all wireless. Only one of them gets a 192.168.1.* IP. The three Windows 7 machines all can see the server despite the fact that two of them have 10.1.10.* IP. The Windows XP computer cannot see the server but that is expected because of the change in how Windows handles networking in the more recent versions.

Because this is a busy office I can't exactly kick people off of their computers and there is not an organized list of machines (like I said, I didn't set this up. If I had, there would a list with every little detail about the machines somewhere). I have half an hour every morning when I come in before most people to do things like diagnose and test. I may have to come in on a Saturday to fix all the tech problems in the office while no one is here.


The question about the IP might be a step in the right direction. Maybe there is something about the way the Macs are pulling their IP that is keeping them from seeing the server. Because I do not have the admin password for the Comcast router, I am planning on connecting the server directly into that router. Although, I do wonder if that would fix this problem.

New update:

I ran traceroute on a Lion Mac with a 192.168.1.* and this is the first part of the results:

1 192.168.1.1 (192.168.1.1) 2.090 ms 1.968 ms 1.891 ms
2 10.1.10.1 (10.1.10.1) 2.999 ms 2.920 ms 3.518 ms
3 --.---.---.1 (--.---.---.1) 35.813 ms 30.894 ms 30.104 ms

Click to expand...

I ran a tracert on a Windows PC which is attached wirelessly but with a 10.1.10.* IP and this is what I got:

1 1ms 1ms 1ms 10.1.10.1
2 38ms 44ms 26ms --.---.---.1

Click to expand...

From what I can tell then is that the computers getting a 10.1.10.* IP are skipping the wireless router entirely (don't ask me how; that is the only wireless router and the one they are connected to). This does not explain why the Windows PC can still reach the server but the Macs can't.

Running tracert on the server gives the same path as the Lion Mac in 192.168.1.* range.

Try this: On the ML Mac, go to System Preferences/Network and choose the Wi-Fi connection. Then choose "Advanced" an on the Wi-Fi tab see if you see more than one network. If the network providing 192.168.1.x IPs is not first in the list, drag it to first position.

I suggest this because you said this:

When I disconnected the wireless on the Lion Mac, I was not able to connect to the server.

Click to expand...

From that I deduce that the machines need a 192.168.1.X IP to connect to the server, but they are getting 10.1.10.1.x instead. Changing priority on networks may get them that coveted 191.168.1.x.

You probably shouldn't post the 76.x.x.x IP address. It's either your fiber optic router WAN IP or your ISP server.

It sounds like you are using the Linksys as a WiFi extender or as a switch to provide more ethernet sockets.
I'd say your network is mis-configured and that is the issue you're having. You have what is called nested networks.
I suggest you make just one (two?) change:
1) Turn off DHCP service on the Linksys.
2) Reconnect the cable from Comcast router to Linksys to be in one of the Linksys LAN sockets, not the WAN socket. This means your Linksys will be a WiFi Access Point, and, an ethernet switch.
End result, all devices will get DHCP IP addresses from the Comcast router, and they will behave like they're all in the same subnet.

(PS - some routers can be put into WiFi Access Point via a setting and then you don't need to change the ethernet socket.)

I agree with you, gsahli, that the network is probably not set up correctly. I found a fix that should last for now. When I am able I may spend a day reconfiguring everything to work without this fix.

The issue:
For some reason (which I am still not sure but the network configuration probably does it), some computers end up with an IP address in 10.1.10.* range (like 10.1.10.17) rather than the 192.168.1.* range (192.168.1.53 is the server's IP). This happens to every computer using a wired connection and some computers on a wireless connection. For some reason, an update in Mountain Lion (I think) made it impossible for a computer in one IP range to communicate with the Windows server in a different IP range even though they are all on the same network and the server could see the Macs on the different IP range. It is also possible that a reset of some network device in the office mixed up the IPs.

What I did:
I manually set the IP address of the two Macs to be in the 192.168.1.* range. This worked. I was not able to change the router IP manually on ML but I was able to for Lion on a wired connection.


For some reason, Windows 7 has no problem with this network issue and can communicate with the server no matter what IP it has. I found that Lion (the older Mac OS) does have issues if it is not in the same IP range.

I will have to keep your idea as an option for when I can spend a Saturday in the office without anyone else here to just fix everything that is wonky on the tech side of things here.

Thanks for the help.