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sharing internet over 2nd ethernet port on Mac Pro

S

slicedbread

macrumors 6502
Original poster
Nov 5, 2006
252
10
Recently got a Mac pro. However my room only has one network socket going into my router, this goes to ethernet port 1. Internet works fine, no issues.

However my old desktop (that the MP replaced) can't get online now - no second network port from the router into the room the computers are in. I have a crossover cable that I've used to connect the 2nd MP ethernet port to the PC ethernet port. However I can't get internet access on the PC.

If the PC and port 2 are on their own subnet (not the router/port 1 subnet) I can get file sharing going between the MP & PC, but cannot figure out how to get the router/MP/PC on the same subnet together using both ethernet ports of the MP. I have already tried enabling internet sharing under system prefs\network, but it doesnt work.

Network:
Router (connected to internet) at 192.168.1.1 - connected to mac
MP port 1 - 192.168.1.2 - works fine in connecting to the net

MP port 2 - 192.168.255.1 - works in networking to PC for filesharing
PC - 192.168.255.2 - works in networking to Mac for filesharing

Any combination of 192.168.1.xxx for the MP port 2 and PC, they can't fileshare anymore and there is still no internet for the PC.

Anyone know how to do this?
 
You could always use the Mac Pro as a proxy server for the PC. Just look around the web for one (make sure you set it up correctly mind it is important) then just configure Internet Explorer with the correct options and you are all sorted. In fact Mac OS X may already come with one (not sure about that).

There are probably much easier and more elegant solutions available but that is the best I can come up with at the moment.
 
slicedbread said:
Recently got a Mac pro. However my room only has one network socket going into my router, this goes to ethernet port 1. Internet works fine, no issues.

However my old desktop (that the MP replaced) can't get online now - no second network port from the router into the room the computers are in. I have a crossover cable that I've used to connect the 2nd MP ethernet port to the PC ethernet port. However I can't get internet access on the PC.

If the PC and port 2 are on their own subnet (not the router/port 1 subnet) I can get file sharing going between the MP & PC, but cannot figure out how to get the router/MP/PC on the same subnet together using both ethernet ports of the MP. I have already tried enabling internet sharing under system prefs\network, but it doesnt work.

Network:
Router (connected to internet) at 192.168.1.1 - connected to mac
MP port 1 - 192.168.1.2 - works fine in connecting to the net

MP port 2 - 192.168.255.1 - works in networking to PC for filesharing
PC - 192.168.255.2 - works in networking to Mac for filesharing

Any combination of 192.168.1.xxx for the MP port 2 and PC, they can't fileshare anymore and there is still no internet for the PC.

Anyone know how to do this?
Click to expand...
Just buy a $20 switch to split the network connection in that room.
Problem solved (just remember to get a switch and not a router)
 
trainguy77 said:
Internet sharing is built into os x. In the sharing preference pane.
Click to expand...

This is indeed what you need to do. If you don't turn internet sharing on then no-go, dude! Also, I don't think you even need a crossover cable, I think the MacPro is smart enough to use a non-crossover or a crossover, but use what you have. If you are getting an IP then you are golden, then just turn on the internet sharing. You do something like, "share this computer's internet over ehternet2."

I'm doing the same thing, but mostly so I can transfer files between two machines at near gigabit speeds...my real world numbers are more like 30MB/s though...hmm...
 
slicedbread said:
If the PC and port 2 are on their own subnet (not the router/port 1 subnet) I can get file sharing going between the MP & PC, but cannot figure out how to get the router/MP/PC on the same subnet together using both ethernet ports of the MP. I have already tried enabling internet sharing under system prefs\network, but it doesnt work.

Network:
Router (connected to internet) at 192.168.1.1 - connected to mac
MP port 1 - 192.168.1.2 - works fine in connecting to the net

MP port 2 - 192.168.255.1 - works in networking to PC for filesharing
PC - 192.168.255.2 - works in networking to Mac for filesharing

Any combination of 192.168.1.xxx for the MP port 2 and PC, they can't fileshare anymore and there is still no internet for the PC.
Click to expand...

to answered directly to your question (to figure out how to get the router/MP/PC on the same subnet together using both ethernet ports of the MP), the answer is you can't.

i tried this before. basically, the MP (192.168.1.100) works like a router in its own subnet and distribute IP to the second port, so this port's IP is 192.168.255.1. the PC is connected to the MP through this port so its IP is 192.168.255.2. now it is in the secondary subnet (like sub-subnet) so it has internet and all, everything worked fine including file-sharing with the MP in both directions. in this sense, this setup works like the "Host-only Networking" option in Parallels.

although this PC can't file-share with another PC (192.168.1.102) that is on the same subnet as the MP, it CAN remote control (via Remote Desktop Connection) this PC. since my knowledge about this area is limited, i couldn't explain why or how it was possible. i just felt weird.

im not sure if im correct, but i guess if you force config the second port on your MP to 192.168.1.xxx, you basically want the MP to work like a switch and not a router anymore - meaning you are telling your router to give your MP two different IPs (192.168.1.100 and 192.168.1.101) at the same time. this is probably impossible due to MP's ethernet card.

an easy answer, like someone above gave you, is to buy a $20 switch. the router will hapily give its ports different IPs of the same subnet (192.168.1.xxx). saved yourself a lot of time and efforts (and headache and hairloss, if any).
 
I used mine for my G4 for a short time. It was just too slow for me. Not to mention all the BS to setup the firewall and sharing. My Linksys wireless router was worth the $50. Plus now my 360 and Wii can all be on my network.
 
The internet sharing pane is so friggin sweet. Makes the internets easy.
Eth1 runs to my laserjet and eth2 shares airport with my SGI. works sweet..
 
I eventually figured out what phuong said as well. You can't get them all on the same subnet.

However 192.168.1.x on one port and 192.168.255.x on the other did work. I DID have internet sharing turned on across the two ports, but it too reboots on both the mac and PC before I got internet on both computers.

Thanks everyone.
 
Sorry to resurrect an old thread but I was wondering...

My ISP will only allocate me one IP address for my cable modem, I can't use my gigabit switch and hookup my cable modem, my ethernet to one computer, and my airport router, and have it work, only ONE iP will work (Airport ot Ethernet). Would it be possible to hook my cable modem to Ethernet Port 1 and Share this connection over Ethernet Port 2 (using Internet Sharing), and hook port 2 to my Airport Express? This way the Airport would be using a shared IP address and my Mac Pro would be using my address allocated from my ISP.

Any idea? I don't have my Mac Pro yet so I don't know if this would work.

Thanks!!

EDIT: I have 3 computers in my house which all have AirPort. I was thinking of getting a Mac Pro without the AirPort card, but my ISP will only allocate me one IP address for my cable modem to be used by one computer (unless I use a wireless router). So can I hook the cable modem to ethernet #1 and share the connection over ethernet #2 to my AirPort Express (allowing me to share my internet connection)??? Much help appreciated. Thanks!!
 
WardC said:
Anyone?
Click to expand...

Your Airport Express is materially no different than the "old" PC mentioned above. Conceptually, you need to create a different subnet (from the one that both either you cable modem may give you and/or the one the Express doles out. )

Your basic problem is that you need a router/firewall connected to your cable modem. The option you are persuing is to turn your Mac Pro into a router. There are cheaper and much lower power consuming home router/firewalls out there, but it can work.
 
Shouldn't an Airport base station do DHCP when configured correctly? You should be able to plug your Airport into the modem and then the gig switch into the Airport. Or am I missing something?
 
SuperJudge said:
Shouldn't an Airport base station do DHCP when configured correctly? Or am I missing something?
Click to expand...

It is an Airport Express. It is the slightly crippled one with only one Ethernet jack.

http://www.apple.com/airportexpress/specs.html

if he plugs the cable modem into the express then the Mac Pro doesn't have something to plug into.
If it was the full size Airport could plug into one of the multiple Ethernet jacks.
 
SuperJudge said:
Totally spaced on that. In that case, just buy a router.
Click to expand...

yeah. If in a larger dwelling one option would be to buy an real airport (or some other router or router/wifi) and use the express to flush out wifi coverage around the dwelling. if a small apartment, want to minimize , and leave the Mac Pro turned on 24/7 then could use the Mac Pro as a router. [ to poster with issue ... note that the Mac Pro can't really be turned off or sleep while it is actively being a router. Not sure how cheap you electricity is but adds up to run it 24/7 without sleeping. ]
 
WardC said:
Sorry to resurrect an old thread but I was wondering...

My ISP will only allocate me one IP address for my cable modem, I can't use my gigabit switch and hookup my cable modem, my ethernet to one computer, and my airport router, and have it work, only ONE iP will work (Airport ot Ethernet). Would it be possible to hook my cable modem to Ethernet Port 1 and Share this connection over Ethernet Port 2 (using Internet Sharing), and hook port 2 to my Airport Express? This way the Airport would be using a shared IP address and my Mac Pro would be using my address allocated from my ISP.

Any idea? I don't have my Mac Pro yet so I don't know if this would work.

Thanks!!

EDIT: I have 3 computers in my house which all have AirPort. I was thinking of getting a Mac Pro without the AirPort card, but my ISP will only allocate me one IP address for my cable modem to be used by one computer (unless I use a wireless router). So can I hook the cable modem to ethernet #1 and share the connection over ethernet #2 to my AirPort Express (allowing me to share my internet connection)??? Much help appreciated. Thanks!!
Click to expand...

If I was in your situation I would buy a cheap wired router. They really aren't that expensive. Then plug that into your internet connection disable NAT and DHCP on the airport and plug that into your router. You then have ports on your router to plug into and you have the airport for wireless. With this setup the wireless and wired appear as a single "network" to the computers so all computers can communicate with eachother.

I see this as the simplest option.
 
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