Cos-to-DSCP:
By default CoS-to-DSCP :
CoS-DSCP map :

cos:   0     1      2      3       4      5     6      7
---------------------------------------------------------
dscp :0    8    16    24    32    40    48    56


Using following command to change this map on switch:

switch(config)# mls qos map cos-dscp dscp1 dscp2 dscp3 dscp4 dscp5 dscp6 dscp7 dscp8

DSCP-to-CoS:
By default DSCP-to-CoS map:

DSCP	CoS
0~7	0
8~15	1
16~23	2
24~31	3
32~39	4
40~47	5
48~55	6
56~63	7

Use following command to check switch map table:
swtich#show mls qos maps dscp-qos

To change DSCP -to-Cos map , use this command:

switch(config)# mls qos map dscp-cos dscp1 dscp2 dscp3 dscp4 dscp5 dscp6 dscp7 dscp8 to cos


Summary: 

DSCP Value	DSCP Name	COS Value
0	Default (BF)	0
8	CS1	1
10	AF11	1
12	AF12	1
14	AF13	1
16	CS2	2
18	AF21	2
20	AF22	2
22	AF23	2
24	CS3	3
26	AF31	3
28	AF32	3
30	AF33	3
32	CS4	4
34	AF41	4
36	AF42	4
38	AF43	4
40	CS5	5
42		5
44		5
46	EF	5
48	CS6	6
56	CS7	7

Note: EF is matching DSCP=46; COS=5 is matching DSCP=40