QoS on 3750

[sasaadamovic]

Hi,

Please see attached diagram with setup.

Links between core and access layer switches, SwitchA and SwitchB, are configured in Port-channel, Here is the interfaces config:

SwitchA

interface GigabitEthernet1/0/49

switchport trunk encapsulation dot1q

switchport mode dynamic desirable

mls qos trust dscp

channel-group 10 mode active

interface GigabitEthernet1/0/50

switchport trunk encapsulation dot1q

switchport mode dynamic desirable

mls qos trust dscp

channel-group 10 mode active

interface Port-channel10

description ----- Channel to MILA-B-3750 -----

switchport trunk encapsulation dot1q

switchport mode dynamic desirable

SwitchB

interface GigabitEthernet1/0/1

switchport trunk encapsulation dot1q

switchport mode dynamic desirable

mls qos trust dscp

channel-group 10 mode active

interface GigabitEthernet3/0/1

switchport trunk encapsulation dot1q

switchport mode dynamic desirable

mls qos trust dscp

channel-group 10 mode active

interface Port-channel10

description ----- Channel to MILA-A-3750 -----

switchport trunk encapsulation dot1q

switchport mode dynamic desirable

We have a deal with MPLS service provider that we can configure QoS marking (DSCP) and they will trust that marking and usid with policy that prioritises traffic. This gives us quite a lot of flexibility.

We have a similar scenario in number of our offices and we have following approach in configuring QoS.

1) We configure policy map on acore switch - policy map marsk traffic

2) Then apply policy map outbound on interface towards MPLS provider router

However this approach is not applicable her because on 3750 switch I can not apply policy map outbound on interface. Therefore I have tried applying policy inbound on core switch to interfaces between core and access switch (to physical interfaces as applying policy map to port-channel interface is not suported on 3570. This would be appropriate as all WAN traffic which needs to be prioritised other then default, is initiated on hosts connected to access switch.

When I try to aply the policy to interfaces, I got following error message:

"Remove policy failed for interface GigabitEthernet1/0/49"

Here are relevant parts of the config:

ip access-list extended Business1 # this is for Video only

permit ip host A.B.C.D any

permit ip any host A.B.C.D

ip access-list extended Business2 # this is for Business Apps

permit tcp any any eq 3200

permit tcp any any eq 3300

permit tcp any any eq 8000

permit tcp any any eq 3600

permit tcp any any eq 8100

permit tcp any host A.B.C.D eq www

permit tcp any any eq 8470

permit tcp any any eq 8471

permit tcp any any eq 8472

permit tcp any any eq 8473

permit tcp any any eq 8474

permit tcp any any eq 8475

permit tcp any any eq 8476

permit tcp any any eq 446

permit tcp any any eq 447

permit tcp any any eq 448

permit tcp any any eq 1414

permit tcp any host A.B.C.D eq 1433

permit tcp any host A.B.C.D eq 1433

permit tcp any host A.B.C.D eq www

permit tcp any host A.B.C.D eq www

permit tcp any host A.B.C.D eq 3389

ip access-list extended Business3 # this is for WamNet

permit ip any host A.B.C.D

permit ip any host A.B.C.D

permit ip any host A.B.C.D

permit ip any host A.B.C.D

permit ip any host A.B.C.D

permit ip any host A.B.C.D

class-map match-any Business1Class

description video traffic class

match ip dscp af31

match access-group name Business1

class-map match-any Business2Class

description Business Apps traffic class

match access-group name Business2

match ip dscp af21

class-map match-any Business3Class

description WamNet traffic class

match access-group name Business3

match ip dscp af11

policy-map MPolicy

description QoS Policy for M

class Business1Class

set ip dscp af31

class Business2Class

set ip dscp af21

class Business3Class

set ip dscp af11

class class-default

Any idea how can I deal with this?

Thanks,

Sasa

[Roberto Salazar]

If the packets coming frm the access 3750 have already have their DSCP marked and on the core which is the exit point to the MPLS provider router is already trusting these packets, why do you want to remark them again? It should just trust those DSCP and retain them. They should not get reset.

[sasaadamovic]

Hi bosalaza,

Thanks for your input.

Not all of the packets are marked, or are marked correctly, before reaching core router. Actually, only video packets are marked correctly (marked on Polycom Video Conference Units), while no other packets are marked.

I need to mark traffic going into WAN as per my access list/class map/policy map so I can control traffic and make sure business apps are protected from WamNet (huge file transfers with WamNet propriatory technology) and VCU traffic, while assuring that this traffic also get the allocated slice of bandwidth.

Regards,

Sasa

[Yudong Wu]

Based on 3750 QoS configuration guide, you can only use one "match" command in class-map.

"Only one ACL per class map and only one match class-map configuration command per class map are supported. The ACL can have multiple ACEs, which match fields against the contents of the packet. "

[sasaadamovic]

Hi kwu2,

Thanks for pointing this out. It definitely clarifies why my configuration does not work.

Any idea how I can implement the QoS, as per my requirement?

Regards,

Sasa