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Both seem the same to me. I don't see how DHCP is different from Dynamic NAT. Can anyone please help?

2

Missing from the current answers is

  • DHCP is a protocol for configuring hosts, and runs periodically to keep their addresses and other configuration up to date. The traffic is between the host and a DHCP server; typically both are on the same local network, but not always.
  • NAT a process is for rewriting packets as they are forwarded across a router. Specifically it translates the addresses and sometimes the ports. The traffic is across a router, typically between an ISP and its client, or between two organisations.
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DHCP and NAT have nothing in common (above "IP-related things"). I think you should elaborate what they actually do that you find similar.

DHCP assigns IP address (among other things), NAT mangles IP addresses (and higher level ports, like TCP/UDP), e.g. translates them to different address range.

  • Dynamic NAT assigns available public IP's from a free pool to the privately connected hosts. DHCP, by what I've read also does the same. – Asma Rahim Ali Jafri Jun 20 '18 at 14:40
  • @AsmaRahimAliJafri, no, that is incorrect. NAT (Network Address Translation) is translating either the source, destination, or both, addresses in network packets. DHCP (Dynamic Host Configuration Protocol) is an off-topic (here) protocol for configuring a host network stack. – Ron Maupin Jun 20 '18 at 16:14
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DHCP is for helping new clients on the network get an IP address dynamically. (Without an IP address, they're helpless.) Dynamic NAT is for translating clients who are already on the network to different IP addresses dynamically. Using this, they appear to the outside world like they have a different address than they really do.

The only common thread between the two is the word "dynamic". When DHCP hands out addresses, it does so dynamically, which means you might get a different IP address next time. When NAT translates you, it does so dynamically, which means you might get translated to a different port number or IP address the next time.

  • So DHCP, is basically done by the ISP? – Asma Rahim Ali Jafri Jun 20 '18 at 14:45
  • An ISP may use DHCP to assign your router a public IP, but that's all. It's then up to you to run DHCP on your router to assign private addresses to all of your household computers/devices. – user3629081 Jun 20 '18 at 14:57
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To put it simply, DHCP assigns IP addresses to hosts in a private network, while NAT converts private addresses into public addresses.

To elaborate, NAT does not assign IP addresses to devices. It does, however, keep a table of IP address conversions, which a router uses to ensure packets between a remote host and a local host are not lost.

NAT is typically used to allow multiple devices on a private network to share a single public IP address on a WAN interface.

DHCP uses a pool of private addresses, such as the 10.0.0.0/8 pool, and these addresses cannot be used on a public network such as the internet. Therefore, NAT must be used to convert a private address, such as 10.0.0.3, to a public address, such as 209.113.65.5, to allow a host on a private network to communicate with a remote host.

  • DHCP is not restricted to private addresses in any way. – jonathanjo Jun 21 '18 at 7:59
  • You are right. NAT, too, is not restricted to my basic definition. – Caine Kiewit Jun 21 '18 at 8:13

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