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COS and DSCP Trust
TheBlueRaja
Member Posts: 12 ■□□□□□□□□□
in CCNP
I have a question about COS and DSCP markings and trust.
Basically I have a 3560 configured to trust DSCP marking. Connected to is is a device which i have prioritised to make all packets with DSCP value 46, this all works well and the values are passed through successfully with markings intact.
However, whilst checking the sh mls qos int Gi0/X stat command i noticed the following:-
GigabitEthernet0/1
dscp: incoming
0 - 4 : 1114846005 0 0 0 0
5 - 9 : 0 0 0 0 0
10 - 14 : 0 0 0 0 0
15 - 19 : 0 0 0 105330 0
20 - 24 : 0 0 0 0 0
25 - 29 : 0 0 0 0 0
30 - 34 : 0 0 0 0 0
35 - 39 : 0 0 0 0 0
40 - 44 : 0 0 0 0 0
45 - 49 : 0 3890398370 0 512960 0
50 - 54 : 0 0 0 0 0
55 - 59 : 0 68503 0 0 0
60 - 64 : 0 0 0 0
dscp: outgoing
0 - 4 : 303064688 0 0 0 2
5 - 9 : 0 114 0 0 0
10 - 14 : 0 0 0 0 0
15 - 19 : 0 0 0 0 0
20 - 24 : 0 0 0 0 0
25 - 29 : 0 0 0 0 0
30 - 34 : 0 0 0 0 0
35 - 39 : 0 0 0 0 0
40 - 44 : 0 0 0 0 0
45 - 49 : 0 3881822239 0 672152 0
50 - 54 : 0 0 0 0 0
55 - 59 : 0 0 0 0 0
60 - 64 : 0 0 0 0
cos: incoming
0 - 4 : 974690360 0 0 0 0
5 - 7 : 0 0 0
cos: outgoing
0 - 4 : 303159564 0 0 0 0
5 - 7 : 3881822242 672152 38048141
Policer: Inprofile: 0 OutofProfile: 0
Basically this shows that i can see DSCP 46 incoming and outgoing as i would expect (there is a similar device at the other end generating EF traffic).
However if you note the outgoing COS, you will see packets with COS values 6 and 7, my COS mapping is as follows:-
Cos-dscp map:
cos: 0 1 2 3 4 5 6 7
dscp: 0 8 16 24 32 40 48 56
So 6 should translate to 48 and 7 to 56.
However in the same output of the stat command above you will see a count of 0 for DSCP 56 yet there are some for 48 (possibly different traffic???).
I suspect that the COS 7 packets are critical network control traffic (red herring?) and it looks like they are being demoted to COS 0 as COS is untrusted.
However i thought that the COS 7 packets should be mapped to DSCP 56.
Im confused because i assume this is important traffic which is being remarked and i expected to see DSCP 56 values of the same number as COS 7 values due to the mappings.
However i think because im not able to trust DSCP and COS that the COS marking are simply untrusted and as a result are marked as 0.
Assuming that this IS network control traffic, shouldnt it also be DSCP marked though?
Lots of questions but i feel this is the blank bit of info im missing which fills inl the QoS blanks i have in my head for my ONT exam.
Basically I have a 3560 configured to trust DSCP marking. Connected to is is a device which i have prioritised to make all packets with DSCP value 46, this all works well and the values are passed through successfully with markings intact.
However, whilst checking the sh mls qos int Gi0/X stat command i noticed the following:-
GigabitEthernet0/1
dscp: incoming
0 - 4 : 1114846005 0 0 0 0
5 - 9 : 0 0 0 0 0
10 - 14 : 0 0 0 0 0
15 - 19 : 0 0 0 105330 0
20 - 24 : 0 0 0 0 0
25 - 29 : 0 0 0 0 0
30 - 34 : 0 0 0 0 0
35 - 39 : 0 0 0 0 0
40 - 44 : 0 0 0 0 0
45 - 49 : 0 3890398370 0 512960 0
50 - 54 : 0 0 0 0 0
55 - 59 : 0 68503 0 0 0
60 - 64 : 0 0 0 0
dscp: outgoing
0 - 4 : 303064688 0 0 0 2
5 - 9 : 0 114 0 0 0
10 - 14 : 0 0 0 0 0
15 - 19 : 0 0 0 0 0
20 - 24 : 0 0 0 0 0
25 - 29 : 0 0 0 0 0
30 - 34 : 0 0 0 0 0
35 - 39 : 0 0 0 0 0
40 - 44 : 0 0 0 0 0
45 - 49 : 0 3881822239 0 672152 0
50 - 54 : 0 0 0 0 0
55 - 59 : 0 0 0 0 0
60 - 64 : 0 0 0 0
cos: incoming
0 - 4 : 974690360 0 0 0 0
5 - 7 : 0 0 0
cos: outgoing
0 - 4 : 303159564 0 0 0 0
5 - 7 : 3881822242 672152 38048141
Policer: Inprofile: 0 OutofProfile: 0
Basically this shows that i can see DSCP 46 incoming and outgoing as i would expect (there is a similar device at the other end generating EF traffic).
However if you note the outgoing COS, you will see packets with COS values 6 and 7, my COS mapping is as follows:-
Cos-dscp map:
cos: 0 1 2 3 4 5 6 7
dscp: 0 8 16 24 32 40 48 56
So 6 should translate to 48 and 7 to 56.
However in the same output of the stat command above you will see a count of 0 for DSCP 56 yet there are some for 48 (possibly different traffic???).
I suspect that the COS 7 packets are critical network control traffic (red herring?) and it looks like they are being demoted to COS 0 as COS is untrusted.
However i thought that the COS 7 packets should be mapped to DSCP 56.
Im confused because i assume this is important traffic which is being remarked and i expected to see DSCP 56 values of the same number as COS 7 values due to the mappings.
However i think because im not able to trust DSCP and COS that the COS marking are simply untrusted and as a result are marked as 0.
Assuming that this IS network control traffic, shouldnt it also be DSCP marked though?
Lots of questions but i feel this is the blank bit of info im missing which fills inl the QoS blanks i have in my head for my ONT exam.