Qos honor

mattsthe2

Say i have Router 1 that is setting and Marking traffic on an interface that is a P2P connection.
Another router, Router 2 that connects to R1 over P2P.
On that connecting interface i have no QoS commands, just a vanillia interface.

When R2 recieves traffic from R1 and sends it out of its LAN interface, which is also Vanillla, no Qos commands, will it Honor the markings that was sent from R1????

I goggled this and got conflicting answers.

Just wondering.

jason_lunde

no...you can mark stuff until your face turns purple...but you have to instruct the router on how to treat a marked packet. Even then, you can make an EF packet have the worse treatment on the network..

or by "honor" are you just asking if it will preserve the markings and send them downstream?

mattsthe2

jason_lunde wrote: »

or by "honor" are you just asking if it will preserve the markings and send them downstream?

You got it, thats what I'm asking.

Heero

unless you instruct the router to, it will not change the markings. It will also not act on said markings.

Forsaken_GA

To expand on this - if every hop had to reclassify the traffic, that would chew up resources and would pretty much make marking the packets worthless. The markings are preserved through the network, this is why best practice is to mark the traffic as close to the source as possible, so that no other machine has to do classification and can just act on the marking as desired.

mattsthe2

Thanks, that makes sense but then i get confused with the 'mls qos trust' command, if this is true why do we sometimes use this command?

Forsaken_GA

mattsthe2 wrote: »

Thanks, that makes sense but then i get confused with the 'mls qos trust' command, if this is true why do we sometimes use this command?

that's usually used to extend the trust barrier to an ip phone. Basically, you want to be able to trust the phones qos markings, but if that phone has a computer attached to it, you do not want to trust it's markings. The trust boundary is (usually) established at the switch, but since the phone can do its own markings, why waste the time and effort for reclassification, just trust the phone. The PC attached to the phone, otoh, is a big no no, which is why you don't want to trust all traffic coming from the port that has a phone attached.