DHCP and NAT

vbimport

#1

i am just bit confused about the functions of there two protocols.

I know that the purpose of DHCP is to assign IP address to compters and NAT is to convert public IP to private IP address but how does it actually work if i am a DSL subscriber that is assign with a dynamic IP address.

He what i understand from what i read in my search, first if a user want to connects to the internet, the DHCP server from the ISP will assign the router with public IP address then the NAT will convert the public IP to private IP… from this point who will assign the private IP to the computers?? (i have my DHCP disabled in the router).

i know i got all this bit twisted up :S…


#2

If you disable the DHCP [U]server[/U] in your router, you will need to manually configure all the IP addresses on your private IP network; i.e. at least the IP address on the router LAN port and on each of your computers.

If you enable the DHCP server in your router (which is the better option for most people), then all computers and devices connected on your private IP network can get their IP addresses automatically from your router via DHCP.

Your router may be set to receive its public IP address from your ISP automatically via DHCP. In this case the router is being a DHCP [U]client[/U] on the WAN side. In some cases you may instead need to use manual IP configuration using information supplied by your ISP - this varies from ISP to ISP but I think the automatic configuration via DHCP is much more common these days.

Using DHCP for private and using DHCP for public IP addresses are really two independent decisions, so be careful to not confuse one with the other.

In most common scenarios, it’s much easier to use your internet router for automatically configuring your private IP addresses via DHCP than it is to do it manually. Most routers even allow you to assign static IP addresses to certain clients (e.g. servers, network storage and network printers).

NAT (Network Address Translation) means that for everyone else on the internet, all your devices looks like just a single device with the single IP address attached to your router’s WAN port.


#3

DHCP and NAT are two completely different things.

DHCP is the Dynamic Host Configuration Protocol. All a DHCP server does is give out IP adresses and ip configuration. Most routers are DHCP servers, which makes it easy to connect devices that are DHCP configured.

A not well configured DHCP server can allow any kind of ip device on your network, allowing devices you don’t want on your network, to access your network.

NAT is Network address translation. All it does is modify the source and destination address of an IP packet. It is generally used to transfer specific things to the right device. For instance: A request for port 80 of the destination address, will be translated to the web server connected to the device having that destination address.

NAT offers no protection, only forwarding.


#4

[QUOTE=Mr. Belvedere;2599243]NAT offers no protection, only forwarding.[/QUOTE] Actually, a NAT router works as a firewall between your private network and the internet, and only allows traffic initiated by you our configured by you.

In my opinion, it offers more useful protection than a software firewall in your computer.


#5

[QUOTE=DrageMester;2599258]In my opinion, it offers more useful protection than a software firewall in your computer.[/QUOTE] NAT can be thought of more as a passive firewall, it does not actively protect or block.