01-30-2012 02:28 PM - edited 03-07-2019 04:38 AM
Hello:
I have a pair of Nexus 7K's running 5.1(3). I have a handful of edge devices that I need to mark ingress traffic, and need to mark both DSCP and CoS. Right now, I have a working config that marks DSCP appropriately:
class-map type qos match-any SAN
match access-group name SAN
class-map type qos match-any NETWORK-CTL
match access-group name NETWORK-CTL
class-map type qos match-any MISSION-CRITICAL
match access-group name MISSION-CRITICAL
policy-map type qos SVR-EDGE-POLICY1
class NETWORK-CTL
set dscp cs2
class MISSION-CRITICAL
set dscp af21
class SAN
set dscp 25
class class-default
set dscp default
interface port-channel61
switchport mode trunk
spanning-tree port type edge trunk
spanning-tree bpduguard enable
spanning-tree bpdufilter enable
service-policy type qos input SVR-EDGE-POLICY1
While that works dor DSCP, the MQC will not allow me to mark both DSCP and COS in the same class, and unlike IOS, it appears that Nexus does not have a default DSCP-to-COS mapping. My understanding is this can be solved using table maps, but I don't see how that can solve my problem in this specific scenario (it appears I can do marking or table-map mutation, but not both?). Can someone tell me how I can accomplish both? Thanks.
Solved! Go to Solution.
01-31-2012 09:45 AM
It will copy the first 3-bit from the TOS field:
AF21 = 18 = 010010 -> first 3-bit of the TOS = CS2
If you use the non-standard marking, it will behave the same:
CS25 = 25 = 011001 -> first 3-bit of the TOS = CS3
No, the internal table-map will do a copy from DSCP into COS inside the dot1q header. Your downstream will be able to match the COS value.
HTH,
jerry
01-31-2012 10:25 AM
I don't believe you can change it with the current release in N7K.
If you are using the newer N55xx, you can set both DSCP and COS. DSCP will be set during inbound when you assign each traffic a qos-group. And COS will be set under network-qos.
Regards,
jerry
01-30-2012 07:39 PM
You can only mark it with DSCP. The system has an internal DSCP-COS map where it will look at the first 3 bit of TOS and treat it with its respective COS value:
CS7 = COS7
CS6 = COS6
EF, CS5 = COS 5
CS4 = COS4
CS3 = COS3
CS2 = COS2
CS1 = COS1
Default = COS0
HTH,
jerry
01-31-2012 09:27 AM
Okay, so what if I use Assured Forwarding PHB, instead of CS markings, such as af21, in the above example? Or if I use a non-standard marking, such as DSCP 25? Is there a show command or documentation that shows the full default DSCP-COS map behavior?
Also, based on your description, it sounds like Nexus is actually not marking CoS in the dot1q header, just treating the DSCP as if it were a COS value? I actually need to mark CoS so downstream switches know how to treat the traffic.
Thanks!
01-31-2012 09:45 AM
It will copy the first 3-bit from the TOS field:
AF21 = 18 = 010010 -> first 3-bit of the TOS = CS2
If you use the non-standard marking, it will behave the same:
CS25 = 25 = 011001 -> first 3-bit of the TOS = CS3
No, the internal table-map will do a copy from DSCP into COS inside the dot1q header. Your downstream will be able to match the COS value.
HTH,
jerry
01-31-2012 09:52 AM
Thanks jeye.
I do have one other question: Is there a way to change this default behavior, say, for example, I want my DSCP 25 marking translated to the dot1q header as COS 4, instead of COS 3?
Also, do the Nexus 55XX switches behave this way as well?
01-31-2012 10:25 AM
I don't believe you can change it with the current release in N7K.
If you are using the newer N55xx, you can set both DSCP and COS. DSCP will be set during inbound when you assign each traffic a qos-group. And COS will be set under network-qos.
Regards,
jerry
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