[SpaceCowboy706]

Can anyone tell me what the purpose of a network bridge is or what itrs used for.

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Hey SpaceCowboy706!

A bridge is commonly used in a couple of different ways:

1) Connecting two or more ethernet segments
2) Connecting two or more individual network devices

Most devices that utilize two or more network interfaces (not including switches/hubs etc.) communicate with others using routing. IP's on the interfaces, routing table, etc. Bridges do not use routing. They will simply take a packet from one interface and dump it out the other. Most wireless devices are bridges that are connected to another interface that will do any required routing. Any IP's assigned to a bridge are for management only.

Hope this helps!
cya. SD

Edited by SoccerDad, 03 August 2005 - 09:14 AM.

[SoccerDad]

Hey SpaceCowboy706!

A bridge is commonly used in a couple of different ways:

1) Connecting two or more ethernet segments
2) Connecting two or more individual network devices

Most devices that utilize two or more network interfaces (not including switches/hubs etc.) communicate with others using routing. IP's on the interfaces, routing table, etc. Bridges do not use routing. They will simply take a packet from one interface and dump it out the other. Most wireless devices are bridges that are connected to another interface that will do any required routing. Any IP's assigned to a bridge are for management only.

Hope this helps!
cya. SD

Edited by SoccerDad, 03 August 2005 - 09:14 AM.

[SpaceCowboy706]

so what would be the advantage of using a network bridge for 5 pc's connecting wirelessly through a linksys router to the internet...

had a home network troublecall yesterday with 5 wireless laptops and the customer had network bridges on all 5 pc's.... wasnt the cause of the loss of connection.... but was just curious why he would have the bridges on there.

[SoccerDad]

He/She should not need any bridging running at all on the client machines. The connection via wireless would be a bridge in itself which occurs between the radio interface on the router and the WAN interface on same. In the situation you are describing, no advantage at all and really shouldn't be there.

ttysoon, SD

[SpaceCowboy706]

so if im understanding this correctly.... the only time you would need a network bridge...

would be if you wnated to share files between pc's without routing through the router...but instead from pc 1 to pc2 directly

[SoccerDad]

That would only work if one of the boxen has more than a single NIC. Normally you would simply connect both machines with a crossover cat5 cable, assign IP's to each NIC and away you go. Bottom line: in 99% of home networks, any type of client bridging is not needed.

I can't find my network imaging tool I used to have, so I'll try this instead:

Wireless Access Points are the best example as they are generally bridges in nature (a wireless router is not):


[Internet] --> [WAN Interface --- LAN Interface] --> [Ethernet interface ---- Radio interface] --> [Client computer]

[] denotes a network device

1) Internet cloud
2) Router - the WAN interface will have an outside, globally routable IP on it. The LAN interface will have either globally routable or private IP depending on your setup. (ie the router is doing NAT for you)
3) Wireless AP - the only IP assigned to this device will most likely be on the Ethernet interface and is there only for management of the device. No routing will be happening.
4) Client computer will have an IP on it, type determined by setup in #2

(One thing I forgot to mention which may bring some clarity: bridges are designed to be transparent to the network; a router is not)

In our setup above, the client machine will send out a packet via the radio (clients wireless NIC) to the AP, which in turn will hand it to the ethernet side on the AP, which in turn hands it to the router. Packet in one side and out the other, regardless of intended destination, with no routing taking place until it actually hits the router. A picture is worth a thousand words here for sure. I'll try to throw something together.

Bridging is also handy for packet sniffing on a network as all packets go in and out of the bridge device as is.

I hope this helps a bit
ttysoon, SD

[SpaceCowboy706]

i got you... i remeber this from school now.