Take the 2-minute tour ×
Super User is a question and answer site for computer enthusiasts and power users. It's 100% free, no registration required.

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 to give network choice priority to LAN other than WIFI in windows 7?) 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

share|improve this question

1 Answer 1

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

share|improve this answer
    
Actually, I ment another advanced settings window, the one that is mentioned in here: superuser.com/questions/321324/… There also is a comment about the difference, but it is not really clear to me... –  Niels Jul 11 '13 at 17:29
    
oh ok. well, that box controls the order in which the routes are inspected, so that if you have two interfaces with a viable route to the same address, they are selected in the order you specify. keep in mind, most routing algorithms are entirely dynamic, so changing the route table isn't an option for many users. additionally many routing advertisement protocols don't consider the monetary cost of a link, so if you have a leased line and a free one, you can elect to have all traffic that can use the free interface do so. –  Frank Thomas Jul 11 '13 at 19:44
    
per the technet article linked in your linked thread, it appears that the position of the adapter does weight the metric evaluation for the local route table, when not participating in a dynamic routing protocol like ospf or eigrp –  Frank Thomas Jul 11 '13 at 20:17
    
So, then how can I know which route the traffic will follow based on the information of the interface order and the metrics? –  Niels Jul 12 '13 at 14:50
    
the interface precedence weights the metric (lowers it), so that unless you are using an dynamic route algorithm, it will generally use the route with the highest precedence adapter simply because it has a better metric. –  Frank Thomas Jul 12 '13 at 15:07

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.