DHCP Router

Apparently, my router can act as a DHCP server.
How does it assign IP addresses if I am only alloted one from my ISP?
I guess I can assign the range I want to use in the router and it
will NAT all WAN requests with that ISP assigned IP right?

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Comments

Webmaster

No NAT involved, just simple 'routing'.

w^rl0rd

So how is my range of IPs distributed to my internal LAN when given only one IP from my ISP.

Don't all of my LAN machines appear as that one IP to the rest of the world unless they are in a DMZ?

Webmaster

Yes, but it not translated (at least not at your router, in some case another router at your isp may use NAT, not likely though.) I would have to if you would use an IP from a public address range which is used on the web already, but in this case you would use a private network range for the inside. When the (cable/adsl access-, not Cisco router) router is configured to act as a DHCP server it will listen to DHCP request on the internal interfaces. The router will have a default route in its routing table which tells it to forward all traffic with as destination an IP address outside your local LAN (many cable/adsl access routers default to 192.168.0.0 with mask 255.255.255.0) to the ouside interface (which has the IP assigned by your ISP).

The following TechNotes explain the difference between a routed and a translated connection:

www.techexams.net/technotes/networkplus/internetconnections.shtml

aznluvsmc

I'm assuming in this question, the router in question is a SOHO based router from Linksys or some other company. In this case, the router has to perform NAT. With only one public facing IP address, the router will have to translate all requests for the Internet.

Webmaster

I'm sorry Warlord, I'm contradicting my own TechNotes here.

You are both correct, the router has to perform NAT because of the private addresses being used on the inside not being known on the outside. I'm not sure what I was thinking

I even mentioned the private address class in the previous post, but still had my PCs public IP address in mind.

Sorry for the confusion...

w^rl0rd

Great! So to sum things up, I can have 10 PCs

192.168.10.2
192.168.10.3
192.168.10.4
192.168.10.5
etc...

while only having my 1 ISP assigned IP.
Cool.

Webmaster

Yes, I have the following setup at home:

{internet}----[cable mode]

[wireless access router]~~~~(PC1, Laptop, Server1)

In my case I can have up to 255 hosts on the internal network (right side of access router) (1 class C IP network).