I want to use cos to configure QoS on Cisco1841.The configuration is lile following.
class-map match-all COS5 match cos 5class-map match-all Mission_Critical match access-group 101
policy-map TEST class COS5 bandwidth percent 50 class class-default fair-queuepolicy-map QOS class class-default service-policy TESTpolicy-map Marking class Mission-critical set cos 5
interface FastEthernet0/0description WANservice-policy output QOS
interface FastEthernet0/1description LANservice-policy input Marking
access-list 101 permit ip host 192.168.0.200 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.
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.
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 ?