auto qos voip trust

[sarahr202]

Hi everybody.

My book says:

" On a switch port acting as an uplink to another switch or router,you should use the " trust" key word.All packets received on that port will be trusted and the QOS information will be left intact"

Rest of network--sw2---f1/1--------sw1------ip phone

So If i configure sw2 as:

Switch(confiig) int f1/1

                     auto qos voip trust

What will sw2 trust cos or dscp ?

Let say sw2 trust cos, will sw2 still calculate dscp value from its internal cos-dscp mapping?

My understanding is auto qos voip trust is macro which enters different qos commands.  For example a switch configured with " mls qos trust cos", still calculate dscp values from its cos-dscp mapping.

Thanks and have a great weekend.

[Vincenzo Errante]

is cos

Table 24-1     Default CoS-to-DSCP Map

CoS value	0	1	2	3	4	5	6	7
DSCP value	0	8	16	24	32	40	48	56

http://www.cisco.com/en/US/docs/switches/lan/catalyst2940/software/release/12.1_19_ea1/configuration/guide/swqos.html#wp1083017

regards

[Reza Sharifi · Accepted solution]

Hi Sarah,

What will sw2 trust cos or dscp ?

If the port is configured with the switchport command, sets the port trust state to trust CoS.

If the port is not configured with the switchport command, sets the port trust state to trust DSCP.

Link to config guide:

http://www.cisco.com/en/US/docs/switches/lan/catalyst6500/ios/12.2SX/configuration/guide/auto_qos.html

Have a nice weekend

Reza