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We have an endpoint which cannot tag outgoing RTP packets as 46 (EF)....

Currently they happily churn out as 0

Can the Cisco switch it is entering, recognise it's RTP traffic and then change the DSCP value to 46 (EF)?

Or, is it only capable of just blanket classification of ingress traffic?

(I only want to mark RTP data, SIP and other protocols can stay as is)

user10021657
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  • What switch or router is it, model? –  Nov 01 '18 at 13:25
  • Short answer: Yes, depending on the device model and SW version – Ron Trunk Nov 01 '18 at 13:26
  • Switch = Cisco 2960 – user10021657 Nov 01 '18 at 13:28
  • Router= 4321 with switching module.... but mainly focused on 2960 – user10021657 Nov 01 '18 at 13:28
  • What SW version? – Ron Trunk Nov 01 '18 at 13:30
  • I can work around the required version (request it).... I am wondering if it's possible ? – user10021657 Nov 01 '18 at 13:32
  • Please post the output of `show version` –  Nov 01 '18 at 13:32
  • Well yes it's possible, but your switch might use a lot of resources to do so. Basically you need to create an access list and match the traffik you've described, then remark the traffic. You can see more about how it's done here: https://networkengineering.stackexchange.com/questions/42660/implementing-cisco-qos-model-to-end-users/45176#45176 –  Nov 01 '18 at 13:36
  • Thanks, that helps a lot.... one of the options we were advised was that we tag our traffic and if it's EF, then it would be sent as EF over the network ... would this approach use less resources, or would it be similar? I don't have the Cisco IOS info as I cannot access the Switch, but it is a WS-C2960XR-24TS-I switch, so I presuming IOS 15.x – user10021657 Nov 01 '18 at 13:43
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    Unfortunately, questions about networks you don't control are off-topic here. –  Nov 01 '18 at 13:46
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    That switch will set everything entering to `BE` as the default. You must configure it to set the DSCP to something else. Also, simply setting something to `EF` does nothing unless you have all the network devices configured to do something with the DSCP values, and, by default, they do nothing with DSCP values. – Ron Maupin Nov 01 '18 at 14:30
  • I don't know why this is locked... I don't have access to the switch because they are on order along with the 4321's.... the test switch we are using at present is a much older 2960, IOS 12.2(44)SE5 ... I know a lot of Cisco functionality is version dependent, but as I said, I can buy in that functionality on IOS 15 if it isn't there .... my question is still valid, without it being as specific as you guys are trying to make it.... if you need a version to work with, use the IOS 12 above, as I can mock it up in the lab and assume IOS 15 will work. – user10021657 Nov 01 '18 at 14:50
  • The reason the question is On Hold is that you cannot access the switch. Questions about networks that you do not directly control are off-topic here. You need access to all the network devices in order to configure your QoS marking and policies on them, and you must configure that on _every_ network device (routers and switches) consistently in order for QoS to function in the network. You want to mark as close to the source as possible, and then use the markings (apply the policies) on your router(s), otherwise marking does nothing for you. – Ron Maupin Nov 01 '18 at 15:28
  • and that's why I said to use the 2960, IOS 12.2(44)SE5 if you needed specifics... I can't get access to something which I don't physically have... I 100% get where you're coming from, but you can still answer the question, as it is specific to a Cisco switch... I wasn't asking about the overall network, or including what is after the switch, which you guys seem to want to steer the answer towards.. – user10021657 Nov 01 '18 at 15:46

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