I've got some questions concerning QoS on access layer 3560 (doing L2) and core 6509 (doing L2 and L3) native IOS switches.
3560: IOS c3560-ipbase-mz.122-35.SE5.bin
6509: IOS c6k222-psv-mz.122-18.SXD7b.bin
- are the 3560 series Switches (doing L2 only) able to trust DSCP on a normal switch/access port? I have found statements that seem to confirm this and statements mention that its only possible on a routed port. Which is true?
- The 6509 native IOS switch is doing L2 and L3 (inter-VLAN routing). I want to trust incoming L2 CoS and preserve/reassign these CoS markings after routing has taken place. Does the (internal)dscp-cos map accomplish this? Will packets leaving the switch be marked with the CoS defined by this map?
The 6500 by default has an internal DSCP-CoS mapping table (show mls qos maps) so if the packet is leaving the switch on an 802.1q trunk then the CoS value will be set according to it's internal DSCP value. If it isn't being transmistted on an 802.1q trunk then the CoS value is still used to determine the queue (On all linecards except the 10Gbps ones which use the DSCP value to determinte the queue I think?). The internal DSCP value is mapped to a CoS value and the CoS then determines the queue. Check with the command 'show queuing interface x/x'.