09-19-2008 02:31 PM - edited 03-06-2019 01:29 AM
Assume the following configuration on a 2970 running 12.2(25)SEB4:
!
no mls qos rewrite ip dscp
mls qos
!
class-map match-any IPTube
match ip dscp 2
!
policy-map IPTube
class IPTube
set dscp ef
!
interface GigabitEthernet0/16
description IPTUBE01
switchport access vlan 31
service-policy input IPTube
!
interface GigabitEthernet0/12
description 3845 Router
switchport trunk encapsulation dot1q
switchport mode trunk
!
G0/16 sees DSCP 2 coming in, but it doesn't seem to rewrite it to DSCP 46 before it sends it to the router (G0/12) and I'm quite stumped.
Note: I'm not trying to police or queue yet, I'm just trying to classify and mark, incase you're wondering about the half-done cofig.
2970#show mls qos int g0/16 statistics | i /|dscp|cos|0 - 4|45 - 49
GigabitEthernet0/16
dscp: incoming
0 - 4 : 0 0 99891 0 0
45 - 49 : 0 0 0 0 0
dscp: outgoing
0 - 4 : 123 0 99891 0 0
45 - 49 : 0 0 0 0 0
cos: incoming
0 - 4 : 99900 0 0 0 0
cos: outgoing
0 - 4 : 100023 0 0 0 0
2970#show mls qos int g0/12 statistics | i /|dscp|cos|0 - 4|45 - 49
GigabitEthernet0/12
dscp: incoming
0 - 4 : 28671 0 119927 0 731
45 - 49 : 0 0 0 416 0
dscp: outgoing
0 - 4 : 21614 0 119927 0 12
45 - 49 : 0 0 0 542 0
cos: incoming
0 - 4 : 149837 0 0 180 0
cos: outgoing
0 - 4 : 142317 0 0 0 0
09-19-2008 02:52 PM
You have DSCP transparency enabled ie. in your config
no mls qos rewrite ip dscp
this tells the switch not to rewrite the DSCP value found in an incoming packet. Try disabling this ie.
mls qos rewrite ip dscp
and see if that fixes your problem.
Jon
09-19-2008 03:10 PM
Hi Jon,
If I disable DSCP transparency, the DSCP value is set to 0:
2970#show mls qos int g0/16 statistics | i /|dscp|0 - 4|45 - 49
dscp: incoming
0 - 4 : 0 0 4145 0 0
45 - 49 : 0 0 0 0 0
dscp: outgoing
0 - 4 : 4151 0 0 0 0
45 - 49 : 0 0 0 0 0
2970#show mls qos int g0/12 statistics | i /|dscp|0 - 4|45 - 49
dscp: incoming
0 - 4 : 346 0 4148 0 111
45 - 49 : 0 0 0 59 0
dscp: outgoing
0 - 4 : 4609 0 0 0 0
45 - 49 : 0 0 0 59 0
I also tried a dscp-mutation map, and got the same results as the priority-map while DSCP transparency is enabled and disabled:
!
mls qos map dscp-mutation IPTube 2 to 46
mls qos
!
interface GigabitEthernet0/16
description AMSQ9IPTUBE01
switchport access vlan 31
mls qos trust dscp
mls qos dscp-mutation IPTube
!
2970#show mls qos int g0/16 statistics | i /|dscp|0 - 4|45 - 49
dscp: incoming
0 - 4 : 0 0 5146 0 0
45 - 49 : 0 0 0 0 0
dscp: outgoing
0 - 4 : 5151 0 0 0 0
45 - 49 : 0 0 0 0 0
2970#show mls qos int g0/12 statistics | i /|dscp|0 - 4|45 - 49
dscp: incoming
0 - 4 : 862 0 5149 0 48
45 - 49 : 0 0 0 27 0
dscp: outgoing
0 - 4 : 6043 0 0 0 0
45 - 49 : 0 0 0 27 0
!
no mls qos rewrite ip dscp
!
2970#show mls qos int g0/16 statistics | i /|dscp|0 - 4|45 - 49
dscp: incoming
0 - 4 : 0 0 5976 0 0
45 - 49 : 0 0 0 0 0
dscp: outgoing
0 - 4 : 7 0 5976 0 0
45 - 49 : 0 0 0 0 0
2970#show mls qos int g0/12 statistics | i /|dscp|0 - 4|45 - 49
dscp: incoming
0 - 4 : 965 0 7649 0 37
45 - 49 : 0 0 0 23 0
dscp: outgoing
0 - 4 : 977 0 7648 0 2
45 - 49 : 0 0 0 31 0
09-23-2008 09:25 PM
But won't the lack of trust rewrite dscp?
Logic is that there is no trust, so everything is set to 0. But when no rewrite was off, it passed through DSCP.
Now rewrite is on, so incoming state is not trusted so internally cos/dscp is 0 (as before) but now there is rewrite on output.
Jason, try to enable trust dscp on the incoming interface where the map is applied.
09-24-2008 06:21 AM
Enabling trust dscp in the ingress interface removes the service-policy from the interface.
As a workaound, I tried to use a DSCP mutation map, but that didn't even work:
!
mls qos map dscp-mutation IPTube 2 to 46
no mls qos rewrite ip dscp
mls qos
!
interface GigabitEthernet0/16
description IPTUBE01
switchport access vlan 31
mls qos trust dscp
mls qos dscp-mutation IPTube
!
2970#show mls qos interface g0/12 statistics | i /|dscp|0 - 4|45 - 49
GigabitEthernet0/12
dscp: incoming
0 - 4 : 71584 0 239989 0 735
45 - 49 : 0 0 0 529 0
dscp: outgoing
0 - 4 : 52419 0 239989 0 103
45 - 49 : 0 0 0 812 0
2970#show mls qos interface g0/16 statistics | i /|dscp|0 - 4|45 - 49
GigabitEthernet0/16
dscp: incoming
0 - 4 : 0 0 244994 0 0
45 - 49 : 0 0 0 0 0
dscp: outgoing
0 - 4 : 308 0 244994 0 0
45 - 49 : 0 0 0 0 0
09-25-2008 08:11 PM
I am not sure I would trust the counters on egress. I would check to see if the packets are arriving at the routers ingress interface with the proper DSCP markings. Switches and counters don't always get along.
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