broadcast domain

hi everyone...i have a qn on broadcast domains...

!) how do we identify a broadcast and collision domain?
like if we have 3 stations connected to router and
a server connected to the router.
where 3 more stations are connected to the server....
there are 4 broadcast and i think4 collsion domains....why?

2)any rules on how we connect usinf a crossover cable? like do we use cross over only for similar devices? like router to router...?

mil thanx in advance....

Bridges and switches segment your collision domains and routers segment your broadcast domains.

You didn't say how you are connected to the router or server. If your router is also a switch (with 4 ports, for example), each port is it's own collision domain (4 of them), but one broadcast domain.

On the crossover, there is an excellent tutorial under the network section.

The cross-over (x-over) CAT5 UTP cable has to be one of the most used cables after the classic straight-thru cable. The x-over cable allows us to connect two computers without needing a hub or switch. If you recall, the hub does the x-over for you internally, so you only need to use a straight thru cable from the PC to the hub. Since now we don't have a hub, we need to manually do the x-over.

You can get the rest here:

www.firewall.cx/cabling_xover.php

hi thomas....
the qn in the book looked like....the router has 4 ports...
and each of the 3 ports has a computer stationed...
and on the last port...a server is connected....and 3 more computers are connected to the server....

could u plz explain how u got 4 collision domains n 4 broadcast domains?

thanx again:)

You need to re-read what I said.

I said "if" you have a router that is also a switch, which many of the low cost routers (linksys, dlink, etc) are, then you have 1 broadcast domain (not 4) and 4 collision domains (each port on a switch is its own collision domain).

If, however, you are talking about a router that has 4 ports (interfaces) then you have 4 broadcast domains.

In this case, as I mentioned above you have 4 broadcast domains (one for each interface). There are 3 workstations off of the server, but you don't say whether they are connected to the server by a hub or switch. If they are connected by a hub - you have 1 collision domain. If they are connected by a switch, you have 3 collision domains.

Take a look at the following page and it might help you understand the difference. Has pictures and everything ( pictures always help me see it ).

www.firewall.cx/hubs.php

hi guys...one of the qns from the exam was about
(1)whether switches reduce the size of collision domain..
i know on a switch...each port is its own collision domain....but does it reduce the size of collision domain?

(2)same 4 bridges right?

(3)whats if a VLAN is implemented....are the broadcast domains reduced in size? what about the collision doamins...i noe the collision domains have increased in number but have they increased in size?

hmm help?thanx

1) Yes. A switch reduces the size of a collision domain. The fact that each port, as you correctly mention, is one collision domain - does not mean that there is only one computer involved. If you were to add a hub onto the port you would still have 1 collision domain at the port, but you may have 5 computers on that 1 collision domain.

2) Yes. Remember that a bridge is a multiport bridge.

3) If you implement a VLAN, you introducing routing into your scheme (which reduces broadcast domain). When you reduce your broadcast domain, you also reduce your collision domain. Increasing the number of collision domains is not a problem, the size of a collision domain is what you care about.

Hope this is what you were looking for.