Routers versus Switches

I am currently living in the dorms at UC Davis. My room mate and I have to share a single internet connection (either T1 or T3). We use a router to split the connection so both of us may use it, but the router is very unreliable for it drops our connection every couple seconds. If I get a switch, will it be able to do what the router is doing for us right now? that is split the connection for multiple users to be on it. Our school requires us to register a MAC address in order to use the internet. Does the switch have its own MAC address we can register or will it auto forward our computer's MAC to the school for authentication?

 

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a router will act as a modem and hub stuck together, if you want to ditch the router then you will need to get a server to run the internet instead.

 

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simply a "Switch" is a "Syncronous hub" as apposed to a normal hub which would "Asyncronous". The difference is that a switch allows heavy network traffic to communicate all at the same time whereas a hub allows some information to go one way then allows some back the other direction before allowing a response etc. (Basically the difference between acting like a CB radio where you can't normally talk and listen at the same time, as apposed to the telephone where you can.)

Routers on the otherhand allow for Network Translation and the direction of packets to the correct Adapter address (MAC). Simply if you have a network at home and you want to share an internet connection then you need to have a Router either acting as the modem or being the first thing the modem plugs into for the network. Switches and Hubs will not cover multiple computers connecting out they are really just meant for internal networking.

What I would suggest doing is sending an E-mail to your Network Administator or looking about your schools website for information on what "MTU" your router should be configured for. The Maximum Transfer Unit (MTU) usually is 1500, however sometimes through routers that size gets Fragmented and you might end up with a size of 1503/1504 trying to go through your router which causes the packet to be dropped.

Usually to optimise to stop packets dropping it means lowering the amount of MTU your router uses to something like 1492 or even 1468 (Notice the numbers are 8 or 32 less here, therefore you should follow the usual "Octal" numerics to avoid odd numbers)

What the size change causes is the router will attempt to shift in small MTU's and makes some allowances for oversized ones which should now be within the 1500 sized constraints.

Hope that helps.

http://www.psc.edu/~mathis/MTU/

 

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Depends on your dorm network, really. If you have a commercial broadband type arrangement, you need a broadband modem/router, check out products by Belkin, Buffalo, and 3Com. (how is the cabling presented to you in your dorm? TP/Cable?)

If the network is part of the private campus network, any hub or switch should do, although a switch is really not needed for just two computers (hubs broadcast incoming traffic to all outputs, whereas switches direct it down specific outputs, depending on configuration).

First thing to try, is borrow a different hub from someone, and see if that solves your problem. Talk to your network admin, and see if you can borrow one from them, and get them to register the MAC address (this is the hub/router address, not the PCs behind it btw).

A few more questions, does the link drop for both of you? (do you see 'Cable Disconnected' for the connection in your systray? Have you both scanned for virii? If you had become infected with some of the latest virii, they can swamp your network connection, although your network admins should have spotted the traffic by now. Run a full scan to be sure anyway.

What OS are you both using? What is the make/model of the router you have now?

 

First off, thanks to both of you for replying. I was just about to order a switch but I'll try your suggestions first.

Stryder, will lowering my MTU to say 1468 reduce my speed significantly? Also by lowering it, any packet over the size 1468 will have to be split up to transfer over in 2 different packets?

Phlogistician, our internet comes to us via Cat5 cable sockets, we just simply plug in a Cat5 and we're up and running as long as we have the MAC address registered with them.
I have a 5 year old hub sitting here and I've tried using it without any success, I believe a possible reason is because it doesn't have a MAC address, in which one is needed to even get online.
The connection drops for both of us simultaneously and the 'Cable Disconnected' message appears.
Virus scans are performed on a weekly bases for both of our Windows XP machine.
The router is a Netgear MR814 v2.

Also, if all fails and I try a switch, do they have a MAC address or does it directly go to the connect computer's MAC address?

 

I simply think the problem is due to packet collision from Asyncronous Transfer. Lowering the MTU does mean more packets however as I mentioned it will mean your Router will drop less.

Since you are using more than one machine anyhow you'd be better off with a smaller packet since any communication to the cable involves both computers defining a single packet currently.

I'm guessing that your Router probably has a Firewall built into it too, thats the main reason why I disconcerned Viruses as being a problem. It is notible that some viruses do mess with the RPC process on modern XP system, however if you have Service Pack 2 installed then you'll have a software firewall that can block out attempts at closing your connection down.

You should remember that you are dealing with a School network and notibly such networks are the first place that "Internet Security specialists" learn their trade, so some packets might be dropped because someones toying around trying to bounce packets with a cloned MAC address.

Switches are defined by "SAMS teach yourself TCP/IP" to be smarter than Hubs, in the sense that they identify each connection to them with a MAC address, it however doesn't suggest that it, itself has a MAC Address since it's not the same as a Router which deals with protocol translation.

 

OK, then you need either managed hub, a switch, or a 'router', as they have MAC addresses. A basic hub doesn't have a MAC address, all it does, is split the incoming signal, and re-broadcast that on it's outputs, and recombine the replies it gets and stuffs them back up the single incoming CAT5 socket.

Seems you need to register a MAC address so the next piece of network equipment allows your traffic. That's nice and secure, and well done your network admins.

Yeah, so it's a basic hub. It could still come in handy. You could register one of your computers MAC addresses with your network guys, and shove an extra NIC (Network Interface Card) in that PC. Use internet connection sharing on your network facing NIC, plug your 2nd NIC into the hub, and the other PC into the hub also. Configure the 2nd PC to use the first as a router (give your 1st PC's 2nd NIC a static IP address, that's in a different subnet to your academic lan, (if they use 10.x.x.x, which is a private address space, use 192.168.x.x and adjust your subnet mask accordingly)) and you have both machines sharing the same connection, although you have to leave the 1st one on for the 2nd to work, and if you have a firewall enables, allow routed traffic.

Cool, borrow some different hardware, and try that.

Good to hear it, check it updates it's virus signature database every few weeks too.

I'll look the manual up, although it does sound like you need new hardware.

The MAC address of the first thing plugged into the socket is what they need to know, as this is what the thing on the other end of that wire sees. So, they need to know what your router's MAC address is.

btw, ignore Stryder, as usual, he's made a post containing lots of impressive sounding technobabble, which solves nothing. Changing your MTU will do nothing if you don't have the right hardware in place. You need to solve that first.

 

Phlogistican,
Changing the MTU, is the first thing to check. It makes more sense doing that than borrowing, buying or stealing other hardware if the problem is just a simple packet drop. (which is exactly what it sounds like.)

My explaination is not a spew of technobabble, it's the same information you would find sourced in countless numbers of manuals and reference material. (Notibly the stuff I've spent years sifting through for my Online dedicated server and home network)

 

Stryder, the problem isn't a simple packet drop, but two separate computers NICs showing the 'network cable unplugged' error (which you failed to ascertain before launching into your pet solution!).

Ethernet networks are designed to recover from lost packets, if you knew anything about ethernet and TCP/IP you'd know that packet collisions are common, and there is a recovery mechanism built into a NIC to avoid and take of this scenario. Packet loss/collisions DO NOT cause the symptoms described.

You completely failed to ask any pertinent questions to diagnose this problem, OS, hardware, how the network is presented, you just launched into spurious technobabble!

I share my broadband connection at home amongst eight computers of various OS's (WXP, W2K Pro and Advanced Server, Solaris, and Linux), and have installed various computer networks professionally. I've only ever had to tweak MTUs once, and that was on a really old IBM PS/2 running OS2, and using TCP/IP over token ring, to get one new application working! I've completed various networking courses, including some pretty hardcore security courses, given by people that advise the MoD, so I know how to diagnose network problems, and the first step, is to listen, and then ask questions, not just blurt out tangential rubbish.

As always Stryder, you use a lot of words, and say nothing meaningful.

 

AHH!! I tried my old hub for the second time and low and behold, it worked!! I'm baffled to why the first attempt did not work though. Anyways, my PC does have two NIC cards and in the past I have also attempted to make my computer a server and having my roomy's plug directly into mine. Correct me if im wrong tho, that this will not work as the 2nd pc needed to plug into mine via a hub/switch or a crossover cable? Thank you both for your generous help too, I have learned a lot more about routers/servers than i ever had in 3 days.

 

Network computers do not access each other directly via the ip address. Instead they send out a packet saying who is this with this IP. the computer responds with this is me and my MAC address is xx:xx:xx:xx. This is because computers on a network connect directly via the card at the network access layer. the tcp/ip layer converts this to the ip that we communicate with. The MAC addressis stored in the ARP table along with the IP so the system knows who it is.

You could try running
arp -s [ip of router]
into a command prompt. which will send out the ARP packet to see who it is...the MAC The MAC address will then be stored,
You can view this by typing arp -a into a command prompt. You can then pass the MAC Address onto the network administrator to add directly. This may solve a few problems with the router.

 

With only two computers you could just use a crossover cable to share your connection. One PC would need two NIC's and would need to be on to share the connection.

 

That is IF he gets his connection via the phone line and not from a TP cable.

 

I like how you use the terms Hub and Router interchangeably there. A hub will not have it's own mac address, a router will. For a person that has so much networking experience mixing those kinds of things up is a bad thing to do.