The motherboard is a Gigabyte one with a Realtek Ethernet controller.
NAT is disabled as I have an IP block and the router is set to distribute this via DHCP. (also have an access point with Xbox and freesat units connected but they are not switched on.
suggested adding a network card if its not suitable for my network which is of course nonsense as Ethernet is an agreed standard.
Just to mention, although Ethernet is an agreed standard, this in no way means all network cards perform equally.
Network cards can have onboard processors which depending on their spec can have larger buffers and offload aspects of packet processing from the computer's CPU, most commonly header data such as checksums (cards for servers usually also handle stuff like VLANs and link aggregation onboard). Whereas cheaper cards (including some of the Realteks) interrupt your processor more often, especially at gigabit rates because they just pass more of the processing on.
However you would not usually notice this unless your computer has an older or slower processor while under high packet-per-second rates. I doubt it would account for intermittent DNS lookup performance.
How are you determining you have DNS lookup problems (a web browser error message that may mention "DNS" or "resolve" is just a generic cover-all message for any number of problems)?. I assume you have also tested the network patch cable or tried a few others.
At the very least you do a visual check for nicks into the cable and wiggle the cable and monitor if the speed / duplex glitches as an intermittent break in the cable would also cause a "cannot resolve this website host" type browser error.
You mention you have NAT disabled but also that you have an "access point". So how big is your public IP block as do you have enough public IPs for every wired and wireless device for the duration of the DHCP lease - regardless if the device happens to be off at some time. This would include smartphones, tablets and any visitors you happened to let on your Wi-Fi as a guest.
Is every other device (including the freesat) correctly picking up valid network settings (they might be expecting private addresses or otherwise causing a conflict)?
Personally for IPv4 I would be tempted to only have public IPs on the things that needed to run internet-facing services, which would not generally include mobiles or indeed Wi-Fi devices generally.
prompt $P - Invalid drive specification - Abort, Retry, Fail? $G
prlzx on n e w n e t: ADSL2+ / 21CN at 3.5Mbps / 800kbps
Edited by prlzx (Thu 30-Aug-12 21:34:31)