2950 no mls qos in config mode !!!!

Unanswered Question
Dec 16th, 2008

hi guys

i just wanna check if i need to upgrade the software or the HW of 2950 switches

i know with these switches i can trust cos or dscp and i can change the default cos-dscp map

however i have switches which is 2950 with iso version 12.1(9)EA1 and 12.1(13)EA1

when i am in config mode there is no commmand start with mls to do mls qos

even in interface level config there is no mls qos trust dscp only trust cos and device

is that becuase of ios version

(config)#mls ?

% Unrecognized command

(config-if)#mls qos trust ?

cos cos keyword

device trusted device class


show version

IOS (tm) C2950 Software (C2950-I6Q4L2-M), Version 12.1(13)EA1, RELEASE SOFTWARE


and 12.1(11)EA1 , 12.1(9)EA1 these sofware versions with those switches i have

thank you

I have this problem too.
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Jon Marshall Tue, 12/16/2008 - 15:56


There is one global config mls command

mls qos map ..

There are 2 interface mls commands

mls qos cos ..

mls qos trust

The "mls qos map .." command is only available with the EI image on the 2960.

The "mls qos trust .." command is available as your config shows but if you want to use the "dscp" option again you need the EI image -



Marwan ALshawi Tue, 12/16/2008 - 16:03

first thanks jon for your quick respons

then my expectation right

because these switches directly connected to edge routers and qos is there

you know with L2 qos only and trust cos not working with uplinks to routers

then do you think better to upgrade ios ?

by the way as long we are in qos thig

i just get confudsed about something

as i know in uplink going from L2 to L3 specificaly router we need to trust based on DSCP

why when we do show mls qos maps

we see cos-to-dscp

thats mean the router capable to map cos values then we can trust the uplink as cos no only dscp???

which is not common ?

thanks again jon

Marwan ALshawi Tue, 12/16/2008 - 16:09

by the way

the switch dose not take mls command at all

thats why i cant do the mls qos map ????

Jon Marshall Tue, 12/16/2008 - 16:13

To use the "mls qos map .." command you need the EI image on your switch.


Jon Marshall Tue, 12/16/2008 - 16:12


The key thing to understand is that switches use an internal DCSP value to "mark" the packets as they pass through the switch.

The COS to DSCP map is used to translate a packet coming in with a COS marking to a DSCP marking that the switch uses to make QOS decisions while the packet traverses the switch.

Note that the internal DSCP value that is used by the switch is never actually written into the packet, it used purely by the switch to prioritise/queue etc. the packet.

So if you trust COS coming in then the switch uses the COS to DSCP map to derive a DSCP value that is used internally. The packet still keeps it's original COS marking.

If you trust DSCP then the internal value is the same DSCP value unless you use a DSCP mutation map.

If you don't trust the marking then the packet is given the default value on the port and this is again mapped to an internal DSCP value.

Hope this answers your question.


Marwan ALshawi Tue, 12/16/2008 - 17:06

hi Jon

thanks again

the thing is what you have mentioned is what i know and understand

the question

if i trust the uplink as cos

and as i mentioned the router has cos to dscp map will the router nap this coming cos based on the map it has ?

or as i know cos when gpo to L3 wil loss its significance ?

if this is the case what is the binifit of the map in the router

is it for marking back from router to switch for example ?

Jon Marshall Wed, 12/17/2008 - 02:22


Apologies for misunderstanding.

Could you just clarify when you talk of a router do you mean a layer 3 switch or a router. And is the uplink to the L3 switch/router a L2 trunk because if it isn't there won't be a COS marking in the packet.


glen.grant Tue, 12/16/2008 - 16:19

Those are pretty old versions but if they are SI versions then you "cannot" upgrade the switch to an EI version . The switch would have to be replaced if you need those options.You should be able to tell with a show version and it will tell you if it is a SI or EI switch , hopefully its a EI . At the very least I would try to upgrade to a newer version even if its SI . 2950 all run the same code but the software is able to recognize whether it is a SI switch or EI switch and it loads the features for that particular switch and there is no way around that .

Marwan ALshawi Tue, 12/16/2008 - 17:03

where is the SI and EI

Cisco Internetwork Operating System Software

IOS (tm) C2950 Software (C2950-I6Q4L2-M), Version 12.1(11)EA1, RELEASE SOFTWARE


Copyright (c) 1986-2002 by cisco Systems, Inc.

Compiled Wed 28-Aug-02 10:25 by antonino

Image text-base: 0x80010000, data-base: 0x80528000

ROM: Bootstrap program is CALHOUN boot loader

WES-L01-C2950-SW1 uptime is 18 weeks, 6 days, 20 hours, 1 minute

System returned to ROM by power-on

System restarted at 14:55:40 GMT Wed Aug 6 2008

System image file is "flash:/c2950-i6q4l2-mz.121-11.EA1.bin"

cisco WS-C2950SX-24 (RC32300) processor (revision C0) with 20402K bytes of memor


Processor board ID FOC0638W01H

Last reset from system-reset

Running Standard Image

24 FastEthernet/IEEE 802.3 interface(s)

2 Gigabit Ethernet/IEEE 802.3 interface(s)

32K bytes of flash-simulated non-volatile configuration memory.

Base ethernet MAC Address: 00:0A:F4:B5:A4:40

Motherboard assembly number: 73-8135-05

Power supply part number: 34-0965-01

Motherboard serial number: FOC06370YHD

Power supply serial number: PHI062800H1

Model revision number: C0

Motherboard revision number: A0

Model number: WS-C2950SX-24

System serial number: FOC0638W01H

Configuration register is 0xF

by the way what is SI and EI mean because it is customer switch i have to explain the featur as well

thank you very much

by the way if SI i need to replace it to whihc switch better with similer capabilitiers and support for EI as well ?


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