newbie-ish networking questions

C

caboosemoose

Gawd
Joined
Aug 26, 2002
Messages
584
Right I need help clearing up a few of my deep rooted networking misconceptions.

1. Routers, switches and hubs. What, precisely is the difference and what precise functions do each serve?

2. One of my home networks setups was essentially a few PCs (all XP) attached to a hub, one of which was an internet gateway. In that scenario I had to manually configure IP addresses to get the PCs to see each other and to share the internet connection. In contrast, I occasionally attach a laptop PC via ethernet to another PC which is part of a homePNA phoneline network. Now, the homePNA network itself does not require you to manually configure IPs when setting it up, and nor do I need to do so when attaching an additional notebook via ethernet to one of the PCs - often nothing is required to get an internet connection, XP usually just picks it up. At worst you have to run the network wizard. So......my question is...for what types of network setups and equipment is manual IP configuration required and why?

Thanks to anyone kind enough to enlighten me.
 
To avoid manually setting IP's you need to have a computer or piece of networking hardware configured as a DHCP server.

Most home ethernet routers do this automatically.
 
Originally posted by caboosemoose
Right I need help clearing up a few of my deep rooted networking misconceptions.

1. Routers, switches and hubs. What, precisely is the difference and what precise functions do each serve?

2. One of my home networks setups was essentially a few PCs (all XP) attached to a hub, one of which was an internet gateway. In that scenario I had to manually configure IP addresses to get the PCs to see each other and to share the internet connection. In contrast, I occasionally attach a laptop PC via ethernet to another PC which is part of a homePNA phoneline network. Now, the homePNA network itself does not require you to manually configure IPs when setting it up, and nor do I need to do so when attaching an additional notebook via ethernet to one of the PCs - often nothing is required to get an internet connection, XP usually just picks it up. At worst you have to run the network wizard. So......my question is...for what types of network setups and equipment is manual IP configuration required and why?

Thanks to anyone kind enough to enlighten me.
Click to expand...

Hubs, switches, and routers >

There is something called the OSI model which details 7 layers to network communications. The difference between these 3 devices can be seen by which layer of the OSI model they each roughly work on.

http://webopedia.internet.com/quick_ref/OSI_Layers.asp

A hub is a dumb repeater. If you have 8 devices hooked into a hub, any information which comes in any port is broadcast out to all ports. It doesn't care about source/destination at all. It has no concept of identifying the devices. So in essence, any bandwidth is shared. A 100mbps hub with 8 devices on it means that if each is using their full bandwidth, they only actually have 12.5mbps (100/8) of bandwidth available. This is a layer 1 device.

A switch looks at the MAC address of every nic on the network and builds a table which says that mac 00-01-0b-ab-03-10-2f-10 is on port 1, so any traffic which wants to go to that nic is sent out ONLY on port 1. So you in essence have dedicated bandwidth. 8 devices on a 100mbps switch gets a full 100mpbs connection speed at all times. This is a layer 2 device.

Finally a router is even a bit smarter. It looks at the IP address of the systems and of the packets of data. So it can say where to send data based on the ip versus fairly complex (and often dynamic) routing tables. So your local network is based on the 192.168.1.x ip scope and the router gets a data packet destined for 65.24.194.8, it knows that this isn't on the local network and sends the packet out the WAN port to the next router...which then sends it a step closer to the destination and so on. These are layer 3 devices.

So in essence, the difference is in how smart the device is. A hub is a moron. Any data packet it gets, it yells out to everyone it can. This is the slowest of the 3 devices due to all of the broadcast traffic. A switch knows what systems are on the local subnet and passes data on based on the mac addresses. This is what you want to use for networking whenever possible because every port gets a full share of the bandwidth. A router moves packets based on IP addresses and is what the internet is based on. They are the most complex of the 3 because they have to keep rather detailed routing tables showing what can be found where.

If you are curious, you have a routing table already on your computer. Go to a command prompt and type "route print" without the quotes. You'll see a very simple routing table similar to what is in any router.
__________________

On your problem, it is due to the fact that you can have network settings built dynamically if you have a device running DHCP (dynamic host configuration protocol). Then a computer is set to "obtain IP configuration automatically" and it sends a broadcast message out requesting the configuration information. The DHCP service gets this request and sends the necessary information such as IP address, default gateway, and subnet mask, back to the requesting computer.
 
Hmm, thanks, that's a start, I feel there's quite a bit of research to be done to really understand how it all works.
 
You must log in or register to reply here.
Back
Top