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I would like to ask what exactly is the difference between the priority settings of network adapters in the advanced settings window of the adapter settings (adapters and bindings, like mentioned in here: How can I force Windows 7 to give my LAN (wired) conection priority over my WiFi?) and changing the metrics in the routing table. So in order to change priority of an interface, I can move it up and down in the advanced settings window, but I could also modify the metrics in the routing table. What exactly is the difference and which one has a higher priority when they conflict with each other? I have read and searched a lot, but I can not find a place that gives me a clear answer, so I hope someone in here knows the right answer.

Edit2: To this question (How to give preference over one network connection over another?), there is an answer mentioning the following:

"Now important thing - changing adapter priority via adapter setting does not change metric. This means it will not change routing decisions!"

But then, what does the setting do and how can I know which route/interface the traffic will follow?

Thanks a lot in advance, Niels

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Niels
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2 Answers2

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Every nic brand has differant settings under the Advanced tab, but for my Intel nic, the "Priority & VLAN" settings relate to the use of QoS (QualityOfService) using the 802.1p protocol, and 802.1Q for VLAN operation on 802.3AC frames.

QoS in particular is not about destination, but about traffic type and susceptibility to latency, so TCP HTTP traffic may be given a lower priority than UDP video streaming. the packet is tagged either on the originating machine or an intermediary system, and the routers/switches/etc the packet passes through subsequently make decisions based on the priority contained therein. a Store-n-forward switch for instance, might push a high priority packet though, without queuing it until all previously received, lower priority packets are sent.

adjusting the Metric in your route table however can only affect the decisions made by your routing protocol, and the selection of physical paths; it does not tag frames as being of high or low priority as QoS does, so there is no decision made based on the type of traffic, just its destination.

so to conclude, QoS is about more than how to get the packet from a to b, but thats all the route table and associated routing protocol care about. see more here: http://en.wikipedia.org/wiki/Quality_of_service

Frank Thomas
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The question is still unresolved at this day. I asked myself this question for the last 5 years and this is what I understand from it:

  • Changing adapter priority is erratically inefficient

  • While changing the Metric value of the Adapter does work.

If your adapters (Ethernet + WiFi) use a different gateway (different subnet), tracert command would tell you what is the next hop (gateway) and you can guess what adapter it used.

In the case both your adapters use the same gateway (so you have two IP addresses from the same subnet), I'd suppose you'll need to monitor the traffic using a network analyser (windump, wireshark) and verify the source mac (or source IP) of outgoing packets

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Florian Bidabé
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