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You are here: MacNN Forums > Hardware - Troubleshooting and Discussion > Mac Desktops > Purpose of Dual Gig Ethernet Ports ???

Purpose of Dual Gig Ethernet Ports ???
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Reggie Fowler
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Jan 26, 2008, 11:40 AM
 
I noticed that on the rear of the new MacPro's they have 2 gig ethernet ports. What's the purpose of having two?

I have a cable modem and i will attach it into one of the ports. What am i suppose to do with the other port?
     
cgc
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Jan 26, 2008, 12:23 PM
 
I can't believe you don't know I don't think you're obligates to use every port on your MacPro, I leave mine empty but maybe I'll plug in an ethernet-enabled coffee-maker...
     
chris v
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Jan 26, 2008, 12:25 PM
 
LAN & NAS? these are "pro" machines, after all, and are made to be functional in server & cluster-types of environments. They're independent channels, so it doubles your throughput if you're reading/writing files to a server or NAS device while communicating with the outside world.

When a true genius appears in the world you may know him by this sign, that the dunces are all in confederacy against him. -- Jonathan Swift.
     
AppleGirl1990
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Jan 26, 2008, 12:55 PM
 
can you plug in two cable modems and get double the bandwidth?
MAC PRO: Two 3.2GHz Quad-Core Intel Xeon 5400 processors
ATI Radeon HD 4870 with 512MB of GDDR5 memory
1600MHz, 64-bit dual independent frontside bus
16 Gigs (4x4) of 800MHz DDR2 memory
     
jamil5454
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Jan 26, 2008, 01:34 PM
 
I believe the Mac Pros support link aggregating so you can have both ethernet ports connected to the same router, but I'm not sure if you can hook up two cable modems at one address.
     
AppleGirl1990
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Jan 26, 2008, 02:11 PM
 
under your scenario, lets suppose you have two ethernet feeds coming from the router into the computer, would you get twice the speed?
MAC PRO: Two 3.2GHz Quad-Core Intel Xeon 5400 processors
ATI Radeon HD 4870 with 512MB of GDDR5 memory
1600MHz, 64-bit dual independent frontside bus
16 Gigs (4x4) of 800MHz DDR2 memory
     
Dork.
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Jan 26, 2008, 02:13 PM
 
Also, some places that use network management protocols like SNMP have a second, parallel ethernet network dedicated just to network management on the subnet. Although this is more of a server issue, maybe the IT guy's workstation needs to connect to both networks....

The short answer is that ethernet ports and chipsets are getting cheaper every year, so why not include two? Would you not buy the Mac Pro because the inclusion of the 2nd Gig-E port put it out of your price range?
     
mduell
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Jan 26, 2008, 04:24 PM
 
Originally Posted by chris v View Post
LAN & NAS? these are "pro" machines, after all, and are made to be functional in server & cluster-types of environments. They're independent channels, so it doubles your throughput if you're reading/writing files to a server or NAS device while communicating with the outside world.
You mean SAN? NAS goes on the LAN.
     
jamil5454
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Jan 27, 2008, 04:17 AM
 
Originally Posted by AppleGirl1990 View Post
under your scenario, lets suppose you have two ethernet feeds coming from the router into the computer, would you get twice the speed?
No, not from the Internet at least. Most home broadband downstream is about 8 Mbps while a typical LAN connection to your router is 100 Mbps, so the bottleneck is in your Internet connection.
     
bballe336
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Jan 27, 2008, 11:15 AM
 
Originally Posted by AppleGirl1990 View Post
under your scenario, lets suppose you have two ethernet feeds coming from the router into the computer, would you get twice the speed?
Well if they are both coming from the same router then they would both be coming from the same internet connection, so it isn't really even possible to have more bandwidth when it isn't there to begin with.
     
drp
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Jan 27, 2008, 11:55 AM
 
Originally Posted by Reggie Fowler View Post
I noticed that on the rear of the new MacPro's they have 2 gig ethernet ports. What's the purpose of having two?

I have a cable modem and i will attach it into one of the ports. What am i suppose to do with the other port?
Given that the target market is professional and business users, it's not surprising that the machine has two network interfaces. There are four main reasons and a handful of smaller reasons to configure a system with two network interfaces:

1) Link aggregation. If both ends of the connection support 802.3ad, then both links can be used to double the amount of bandwidth to a given system.

2) Dual-homed DMZ configuration. One interface is connected to an private management network and the other interface is connected to the Internet. This means that the Internet facing network can have very restrictive access control via the firewall and the management network can be more relaxed to allow the machine to access other resources like database servers, file servers, etc.

3) Hot standby. Each interface is connected to a redundant switches on the same network. If one link fails, the machine will automatically switch to the other link. This would normally require Mac OS X Server, but could be hacked to work on normal Mac OS.

4) Heartbeat. Two identically configured machines with access to the same storage and applications use the second interface as a heartbeat network to monitor each other. If the heartbeat disappears (and other factors are met) the standby machine takes over doing the work of the failed system.

There are some other "gee I have to network interfaces, what cool things can I do with them..." scenarios, but the above is about 80% of why people specify having two.
     
Tesselator
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Jan 28, 2008, 08:31 PM
 
Originally Posted by AppleGirl1990 View Post
can you plug in two cable modems and get double the bandwidth?
I think maybe you can. I have a 120megabit internet connection and will soon be getting a 240megabit connection. I'll have about a two month overlap where I'll have both connections (different lines, different ISPs) and I'll give that a try. In Windoze there is an option to "bridge" multiple connections like that and I think that's kinda what it's for. Correct me if I'm wrong. So I guess there is a way to do that on a Mac as well - though I haven't seen the option displayed in any configuration panel of OS X 10.4.x or 10.5.x.
     
Simon
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Jan 29, 2008, 04:34 AM
 
What you referred to as "bridge" is called link aggregation or IEEE 802.3ad standard.

It's very simple to enable in OS X. Search for "Combining Ethernet ports" in Mac Help.

• System Preferences > Network > Action pop-up menu > Manage Virtual Interfaces > + > New Link Aggregate
• Select the Ethernet ports you want to combine, give the aggregate service a name, and then click Create
• Click Apply Now to activate the new virtual Ethernet service

If somebody here is planning to do this to increase network throughput by connecting both ports to a network switch, keep in mind that the switch must be configured to allow link aggregation. If it's not and you try to do it nevertheless, chances are you'll have no network connection at all. Accordingly, if you connect both ports on your MP to a switch, set up link aggregation (as detailed above), and then lose you network connection, chances are you're switch isn't set up to support link aggregation. Talk to your network admin.
( Last edited by Simon; Jan 29, 2008 at 04:40 AM. )
     
Cadaver
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Jan 29, 2008, 10:39 AM
 
But just to be clear, connecting two cable modems to the cable coming in to your house and using both ethernet ports will not increase your internet access speed. You're still limited by the bandwidth coming in to your house, not by how many ethernet ports the cable modem has.

Now, if you were to subscribe to two independent ISPs, say Verizon FIOS and Comcast cable, then perhaps you'd see some improvement - though it would be way more expensive than just subscribing to one ISP's higher tier service.
     
Macadvo
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Jan 30, 2008, 11:38 AM
 
I just tried linking my Eth01 and Airport, it wouldn't let me. lol
Mac Pro Quad 2.66Ghz with 5Gb memory, 2.2Tb internal HDD, 750Gb external HDD and 30" Apple Cinema Display
     
Simon
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Jan 30, 2008, 12:18 PM
 
Well, duh. 802.3ad requires two Ethernet connections, not just any two network connections.

Your post reminded me of that guy who built a soft RAID with 5 USB floppy disk drives.

     
Andrew Stephens
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Jan 31, 2008, 08:32 AM
 
Originally Posted by Simon View Post
Well, duh. 802.3ad requires two Ethernet connections, not just any two network connections.

Your post reminded me of that guy who built a soft RAID with 5 USB floppy disk drives.

Joyous!
     
Reddog99
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Feb 4, 2008, 03:06 AM
 
For my own setup, I use one port to connect to my wireless router (100 Mbps coming from the cable modem). I use the second port to connect to my nearby pc. I have the pc set up with two NICs also. This way, my connection to the pc isn't slowed down by needing to go thru the router. This all wouldn't be necessary if the router speed was gigabit, but those are still a bit expensive, and this is easy.

Pat
     
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Feb 4, 2008, 10:16 AM
 
Originally Posted by Reddog99 View Post
For my own setup, I use one port to connect to my wireless router (100 Mbps coming from the cable modem). I use the second port to connect to my nearby pc. I have the pc set up with two NICs also. This way, my connection to the pc isn't slowed down by needing to go thru the router. This all wouldn't be necessary if the router speed was gigabit, but those are still a bit expensive, and this is easy.

Pat
I have a D-Link gigabit switch that was like $60.

Cable modem -> wireless router (Apple Airport) -> gigabit switch -> hardwired machines

This way, the hardwired machines still share 1000Mbit connectivity to each other and the router can supply an IP address to everything.
     
   
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