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set cos on Cisco1841



I want to use cos to configure QoS on Cisco1841.The configuration is lile following.

class-map match-all COS5
match cos 5
class-map match-all Mission_Critical
match access-group 101

policy-map TEST
class COS5
  bandwidth percent 50
class class-default
policy-map QOS
class class-default
service-policy TEST
policy-map Marking
class Mission-critical
  set cos 5

interface FastEthernet0/0
description WAN
service-policy output QOS

interface FastEthernet0/1
description LAN
service-policy input Marking

access-list 101 permit ip host any

WAN Network is Ethernet-based-VPN ( L2 Network)

I tryed set configuration noted above on Cisco1841 fa0/0 and fa0/1,however, the error shows "Set cos not supported in input policy"  "'match cos' supported only with IEEE 802.1Q/ISL interfaces."

If Catalyst 3750 etc, I understand that CoS is available on FastEthernet interface.

Does anyone know how to use cos on Cisco1841 ? ( I can't use DSCP and IP Precedence)

Are there any interface card or module which enable cos setting on Cisco 1841 ?

Thanks in advance.

Hall of Fame Cisco Employee

Hello Shouichi,

It does not make sense to do set cos on an input interface of a router. The entire frame header in which the CoS would be rewritten is basically ignored as soon as the router starts to route the packet. Writing a new CoS there would be useless. Moreover, when the packet is being sent out a different interface, it is encapsulated in a new frame - and depending on the link layer technology, that new frame may not have a CoS field at all. Therefore, the CoS can be set on an outgoing interface only.

Furthermore, the CoS marking in Ethernet is possible only on 802.1Q tagged frames. As the configuration of a physical interface on a router (the Fa0/0, Fa0/1) processes untagged frames by default, it is not possible to deal with CoS on a physical interface directly. If you want to match or set the CoS bits, you have to create an appropriate subinterface, define the VLAN and apply your policy-map on the subinterface. Obviously, the interface on the Cat3750 has to be configured as 802.1Q trunk.

Best regards,



Thank you for your answer.I could understand the technical background for your explanation.

If I install HWIC-4ESW in Cisco 1841, Can I use COS setting?

(Off cource,as you mentioned, I have to set Interface-vlan.1 interface-vlan.2 instead of physical interface.)

HWIC-4ESW seems to support 802.1q, 802.1p.

Can I configure COS on Cisco1841 as Catalyst ?