routers??

hey Guys,

i just wanted to start this thread as i thought it could lead to an interesting discussion, as i have found it hard to find the answers to my questions on the internet. as, recently, i have become very interested in the intricacies of computer networks.

in particular i have become interested in the operation of routers, as these are the more complex networking devices, as apposed to hubs, bridges and switches. i am fairly confident that i understand the operation of basic LAN routers that are responcible for a subnet of a LAN.

therefore, i particularly wanted to discuss the operation of home network routers, or for that matter any router that uses NAT or any variation thereof. so, i was wondering if anyone could describe how NAT and PAT/NAPT work?


regards,

- user0182

http://en.wikipedia.org/wiki/Network...ss_translation

hey SirDice,

obviously, i have read this article. what i really need is to set up a LAN, where i can play with these things.

but, i was wondering about things like; if i were to write a client server application where the client program sent data to the server on a certain client port then the server read that data and responded to a different client port, and the client machine was sitting behind a router using NAPT Overloading, am i right in assuming that this would not work and confuse NAPT?

thus, any server that tries to send a response to a different port than the port that the request was sent from would fail where NAPT is involved? as a router using NAPT, maps client "IP Address/Port combinations" to it's own router ports.


- user0182

btw - i also wanted to ask what networking hardware you guys consider to be the best, Linksys, Belkin, Netgear, D-Link etc.

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obviously, i have read this article

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Did you?

I gave the article a good read-through and under this heading Basic NAT and PAT is a link to Network Address Port Translation, NAPT which links to another article that breaks NAPT down fairly well.

In this linked article, I found this under Translation of the Endpoint:
"Otherwise, if the destination port number of the incoming packet is not found in the translation table, the packet is dropped or rejected because the PAT device doesn't know where to send it"

Which answers this:

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thus, any server that tries to send a response to a different port than the port that the request was sent from would fail where NAPT is involved?

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Am I missing something here?

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Originally Posted by user0182

obviously, i have read this article. what i really need is to set up a LAN, where i can play with these things.

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No need, install VMWare server. Install one or two basic bsd/linux VMs in it and you've got enough to play with..

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but, i was wondering about things like; if i were to write a client server application where the client program sent data to the server on a certain client port then the server read that data and responded to a different client port, and the client machine was sitting behind a router using NAPT Overloading, am i right in assuming that this would not work and confuse NAPT? thus, any server that tries to send a response to a different port than the port that the request was sent from would fail where NAPT is involved? as a router using NAPT, maps client "IP Address/Port combinations" to it's own router ports.

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Look into how an active FTP works if you're behind NAT (or better why it doesn't work).

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btw - i also wanted to ask what networking hardware you guys consider to be the best, Linksys, Belkin, Netgear, D-Link etc.

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Cisco.. But then.. We have to manage about 10.000+ routers and switches. That's a whole different ballgame compared to a run-of-the-mill home setup ;)

by "obviously", i just mean't that doesn't everyone check Wikipedia first? i did read the Wikipedia page, but i didn't read every article that it linked to.

i just wanted to check with you guys that i had understood what i had been reading, as i'm sure it is possible to read something and think that one has understood it, but still be mistaken.

i'll look into the FTP thing, SirDice, but i did read something about it. as i understand, FTP won't work throught NAT because the packets include IP Address information in the actual packet data, above the Network layer?

anywho, i was wondering what peoples opinions of networking hardware is and which is considered to be the best? i've been reading various product descriptions, for switches and routers, and at the moment i'm thinking that Linksys might be a good way to go, to run a multi-OS network (Linux, BSD, OS X, XP, Vista etc), what do you guys think?


regards,

- user0182

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anywho, i was wondering what peoples opinions of networking hardware is and which is considered to be the best

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Well, we use a Cisco firewall and once you learn to configure it, it's a very solid solution. And for workgroup switches(for extending your network), Linksys products have worked great for us. As for main switches, I like the Cisco Catalyst Series.

The only thing is, you're dealing with a multi-platform, multi-vendor network. I deal with all Windows based platforms so I don't know how well everyone would play together under your network.

Networking equipment has feck all to do with what OS your clients/servers are running.
Routers/switches work with TCP/IP and are totally oblivious as to what OS you happen to run on your workstation/server.

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Networking equipment has feck all to do with what OS your clients/servers are running.
Routers/switches work with TCP/IP and are totally oblivious as to what OS you happen to run on your workstation/server

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I was speaking more of a management perspective. As in, how different OS's interact with the equipment itself via GUI, 9-pin, etc. But hey, thanks for the Networking for Dummies lesson! :rolleyes:

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Originally Posted by ShagDevil

As in, how different OS's interact with the equipment itself via GUI, 9-pin, etc.

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Not really OS dependent now is it? Most, if not all, GUIs on networking equipment are web based.
It works exactly the same on Freebsd, Linux, windows, whatever.. 9-pin? Ah.. Serial.. Same deal..

I have never ever seen network equipment that's only manageable if you use a certain OS.

The great thing about TCP/IP is... is it's OS independent.. So why make equipment that only works (manageable) with a certain OS?