Reading CCIE Practical Studies Volume II on Safari I thought I’d check out mls qos on the 3550 I have in my CCIE lab. Being familiar with the QoS mapping on a 6500 (sup720) and a 4500 (sup IV?), I was surprised to find something I’d not seen before:
- Policed-dscp map
So I started searching for what it’s for and I quickly found the following information.
QOS Policing and Marking with Catalyst 4000/4500 IOS based Supervisor Engines – Configuring and Monitoring Marking:
! police and mark down all other ip precedence 3 traffic
__police 1 mbps 1000 exceed-action policed-dscp-transmit
The 3550 can remark dscp when policing and it uses a special qos-map to do so. Unlike routers where the remark can be stated as:
__police cir 128000
____exceed-action set-dscp-transmit cs2
I must admit the 3550 way can be quite handy as the stated router config will just plainly overwrite the existing marking while the qos-map will look at the dscp value to map from.
Here is another useful link about QoS on a 3550