This question came up in a reply to another tutorial:
what if i m using dynamic IPs. do they change frequently? i just need to know the difference between dynamic and static IPs and please be specific.
The answer merits a small tutorial, with a proper title, so everyone can find it.
Static IPs are assigned to a networked device by the administrator of that device. The network administrators need to keep track of what IPs have been assigned. This leads to organized and planned IP addresses:
- Printers and scanners XXX.YYY.ZZZ.20 to 29;
- Wireless routers XXX.YYY.ZZZ.30 to 34; et cetera.
My NAS is always XXX.YYY.ZZZ.35, my laserjet is always XXX.YYY.ZZZ.30.
Dynamic IPs are assigned by
Dynamic Host Configuration Protocol; DHCP. You get what you are given, typically for 24 hours.
A variation of DHCP called
Static DHCP will set aside preferred IP addresses for certain devices and hold that IP until all IPs in the general pool are tied up. When that happens it will assign preferred IPs to other computers.
IP assignments include:
- IP
- DNS IP
- Default Gateway
- Subnet mask
DNS IPs can change, making Static IPs impractical for computers. DHCP reassigns DNS IPs when they change.
Static IPs make troubleshooting easier. You know X IP = X device. IF you have the documents up to date.
Dynamic IPs change, so you look for
Bobs Laptop
and see what the IP is, instead of
ping XXX.YYY.ZZZ.18
- Static IP for devices that are always on; well documented
- DHCP for computers that get turned on and off.
- Static DHCP for the best of both worlds.
Static DHCP tutorial Best practices:- Assign Static IPs in blocks by device function: Printers and scanners, Wireless devices, Storage
- Assign a block of DHCP addresses that does not overlap other blocks. If you do not want guests on your network assign as many IP addreses as you have computers so there are no addresses available for freeloaders.
- Static IP devices should be on before the DHCP server, so the DHCP server can find IPs currently in use.
- After a power outage, reset the DHCP server after all Static IP devices are up.
- Turn DHCP devices on after the DHCP server is up
Static, Dynamic, and Static DHCP IPs compared 
Linear Mode
