Questions on Routers

[Dreamscape]

I set up a neighbors wireless router. Never did anything like that before, but have seen enough to fake my way through it. It was one of those Linksys thingies that seem to be a popular brand. Anyway, I was wondering about the details of how it worked. I know the router in effect takes the normal IP address provided by whatever means it is usually gotten and creates fake ones for all computers hooked up to it.

• Do the IPs assigned by the router have to be within the range of unassigned IPs or does that matter since no outside computer sees them?
  
• How does the router avoid collisions? This is a bit broad and too complicated to explain, but for example suppose two computers on the router network act as ftp servers and run on the same port. I assume the connection address would be the same (the routers address), but which would the client connect to? In fact, could both run as ftp servers if the ports were different? I assume traffic can be redirected by ports?
  
• When you put a computer into the DMZ, what is its IP address? Is it the address assigned by the router or the address assumed by the router? For example, if one computer hosts a game, I assume outsiders would connect to the routers IP address and you would tell the router to funnel all communication on port "X" to go to computer aaa.bbb.ccc.ddd?

As you can imagine, I have alot of spare time

[HAL9000]

The router will assign IP's in the range of 192.168.0.XXX (ummm... seems to me the 0 can be changed... would have to take a look).... When you use DMZ, you take the IP assigned to the machine you want open on the net... say for example 192.168.0.50 and use that number in the router (I also prefer to statically assign that IP to the machine to avoid any hassles). That single machine will now be open and visible to the internet.

[Dreamscape]

Does that tacitly mean that only one computer at a time can be in the DMZ, since it assumes the routers IP?
Also, what is statically assigning an IP?

[ktkendall]

Statically assigning is when there is no DHCP server available and U must manually go into network settings under TCP/IP for your network adapter and type in the IP address and subnet mask and default gateway and DNS server IP addresses.

[HAL9000]

As far as I know... the router will only allow one machine to be DMZ.

[lil Jimmie]

A router will use routing tables to direct traffic/packets it's kinda like a map of the network in it's memory.

[mbossman2]

Originally posted by Dreamscape [*]How does the router avoid collisions? This is a bit broad and too complicated to explain, but for example suppose two computers on the router network act as ftp servers and run on the same port. I assume the connection address would be the same (the routers address), but which would the client connect to? In fact, could both run as ftp servers if the ports were different? I assume traffic can be redirected by ports?

A routers themselves (2 port, 1 LAN and 1 WAN port) do not prevent collisions per se as the 2 ports are generally full duplex ports. Routers that have multiple ports (1 WAN and 4 LAN ports) generally incorporate some kind of switch technology (we can really get into it if you want let me know).

Now with the issue of 2 FTP servers running on the same network utilizing the same TCP port: Remember, there are multiple entries within an IP packet. The TCP/IP info is embedded fairly deeply in the packet itself and the routers and switches of a network generally only go as deep as the MAC address and IP addresses (most sophisticated routers, switches and other network devices can and do go deeper but again another topic) and make the routing and switching decisions on those 2 pieces (routers on IP address and switches on MAC address and those 2 pieces are sufficient enough to identify which of the 2 FTP servers is the destination for that traffic.

Port redirection can be done and is a feature in many routers and firewalls as long as they are layer 4 "aware" (not really but lets leave it at that shall we).

HTH