Ask away :) You are correct, in that the voice packets will have a 802.1Q header, after that is negotiated via CDP between the Cisco switch and the Cisco phone. You should also ensure that if any packets are received with the voice VLAN in the header, but are NOT from the phone, they are marked down to default/0. To answer the second question, if there is no "voice vlan" configuration, then you would potentially want to trust DSCP. The issue would be that other devices behind the phone would also be trusted.
Note that you should also configure "mls qos trust device cisco-phone" on the 3560s and 2960s. It will also be needed on version 2 of the lab, since 12.2(33)SXI code support it. The version 1 code doesn't support it. Jason Boyers - CCIE #26024 (Wireless) Technical Instructor - IPexpert, Inc. Mailto: [email protected] -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Kristján Ólafur Eðvarðsson Sent: Tuesday, August 16, 2011 1:18 PM To: [email protected] Subject: [OSL | CCIE_Wireless] Very basic wired phone QOS question I can´t believe that I am asking this but what the the heck :D A cisco phone connected to a switch. ! switchport mode access switchport voice vlan x switchport access vlan x ! I have somehow considered the phone to send COS layer 2 packets on the voice vlan because the phone is actually trunking (after negotiating voice vlan with cdp) data and user vlan. ! However the port is in access mode (as it looks) and show int status shows that clearly.. ! I have a question in my practice LAB that wants layer2 ports and interswitch links to trust cos and layer3 interfaces to trust DSCP. ! Am I not right to trust cos on the phone port ? even though it seems access it is sending COS layer2 tags on the packets right ? Another bonus question if the phone didn´t have the switchport voice vlan but only a access VLAN it would sit on. Would that still be mls qos trust cos ? regards. Kristjan _______________________________________________ For more information regarding industry leading CCIE Lab training, please visit www.ipexpert.com Are you a CCNP or CCIE and looking for a job? Check out www.PlatinumPlacement.com _______________________________________________ For more information regarding industry leading CCIE Lab training, please visit www.ipexpert.com Are you a CCNP or CCIE and looking for a job? Check out www.PlatinumPlacement.com
