What confuses me, is that I have set my Sky+ and PS3 to use a fixed IP without these problems but then again, these are connected via cable. Obviously WiFi must be different.
Wi-Fi isn't different as regards how DNS works, but there are different use cases.
1) If this is a portable thing such as a laptop or mobile, that you intend to use in other locations:
You are unlikely to want manual IP settings on the wireless interface as you would always have to change that setting when connecting to a different Wi-Fi network. This includes not setting manual DNS settings (even public DNS) on the wireless interface as that is not necessarily suitable on every network.
2) If this is a device that is going to stay put:
Even then it's better to leave network settings on auto unless you know why
you need to change something. DHCP gives out more than just IP addresses.
If you want to set DNS by hand, as has been said just set DNS to point to the IP of the local router that connects to the internet. On the router make sure the (WAN) DNS settings are valid for the ISP it connects to, or use public DNS.
3) Note that on most devices, setting a secondary DNS is not mandatory. What happens if you leave it blank?
4) By default home routers provide DNS settings to DHCP clients. Most routers work as a DNS forwarder so they give out their own address.
Some routers will also provide a local DNS service (device names collected from DHCP clients) that can make it easier for devices to find each other within your home network.
They can also provide DHCP Reservations (a table of fixed IPs to MAC Addresses),
other info such as MTU and a time service (NTP); so that these settings are held in one place rather than all over the shop.
5) If the device also has a wired network interface, make sure you aren't changing the settings for that instead - surprisingly easy to do. I say this because not everyone realises IPs are not per device but more per network interface (or even several per interface).
Leave the wired interface settings on auto. Definitely do not try to set the same IP address there, nor a gateway (router) address.
6) If you are using Chrome as your web browser, it tries to be smart about looking up DNS names. But if it has already decided it can't resolve a DNS name to an IP address it might not try again after you change the settings, You can try CTRL-R to refresh but sometimes you have to close and reopen the browser.
The PC has a local cache of DNS responses that can also show the same kind of behaviour. After changing DNS settings, you can do
(in Windows) in a Command Prompt
Some versions of Windows require you to open Command Prompt
using Run As Administrator
for certain command.
7) If you do set your IP addresses by hand, it is up to you to make sure there is no duplication, nor that any manual IPs clash with any auto IPs. Mobiles or tablets (or other guests) on Wi-Fi will still need DHCP unless you enjoy doing it the hard way!
In this case you will need to adjust the router's DHCP settings to leave space for the fixed ones.
For example if the router is on 192.168.1.1 and gives out 192.168.1.2-254 youil have clashes.
You can divide it up however you want. An arbitrary example for 192.168.1.x
x =1: router (default)
x=2-9: keep free - routers / switches etc
x=10-99 fixed IPs
x= 100-199: DHCP range
x=200-249: more fixed IPs
x=250-254: keep free - routers / switches etc
I think many people who tweak like to come up with their own numbering plan.
Note that most home routers are either at .1 or
.254, and that .0 and
.255 have special meanings.
This is a rather formal example but does show why DHCP reservations are easier as this is in one place on the router rather than in your head or on bits of paper.
prompt $P - Invalid drive specification - Abort, Retry, Fail? $G
prlzx on n e w n e t: ADSL2+ / 21CN at 2.5Mbps / 800k
Edited by prlzx (Wed 29-Feb-12 16:25:53)