At 06:08 PM 4/22/2002 -0400, Hassan, Shehzad wrote:
>Ian,
>I agree with you that the box shud retain its TOS/DSCP value but I dont
>think Cisco 6509 retains the TOS value with QoS turned Off,
>I chatted with a couple of freinds and thye have experienced same, but need
>some documented proof.
There has been a couples of bugs which are resolved before the release you
quote whereby the show commands were showing the incorrect state in regards
to qos being disabled or enabled. The behavior of the 6500 when "mls qos"
is disabled is that all packets ToS/DSCP values are left unchanged, as soon
as qos is enabled if a trust state or acl is applied to the interface the
packets are written to zero.
If you need written references:
CatOS
http://www/univercd/cc/td/doc/product/lan/cat6000/sw_6_3/confg_gd/qos.htm#xtocid37
Supervisor IOS
http://www.cisco.com/univercd/cc/td/doc/product/lan/cat6000/ios127xe/qos.htm#xtocid25
Look under With QoS disabled, the interface trust state is trust dscp,
which means the IP precedence and DSCP values will not be changed.
Now to verify with testing:
Test Topology:
Traffic Generator ----> Gig4/1 6500 --> Gig 4/2 ---> 7200
Traffic generator sending traffic with ip precedence 0 and 4
With qos disabled globally on the 6500
melbourne#sh int gig 6/0 precedence
GigabitEthernet6/0
Input
Precedence 0: 47616 packets, 2095104 bytes
Precedence 4: 1220 packets, 53680 bytes
With qos enabled globally on the 6500
melbourne#sh int gig 6/0 precedence
GigabitEthernet6/0
Input
Precedence 0: 31240 packets, 1374560 bytes
Ian
>SH
>
>
>
>-----Original Message-----
>From: Ian Cox [mailto:icox@cisco.com]
>Sent: Monday, April 22, 2002 5:53 PM
>To: Hassan, Shehzad; Cisconsp (E-mail)
>Subject: Re: [nsp] TOS/DSCP marking on 6509 SUP
>
>
>At 10:44 PM 4/21/2002 -0400, Hassan, Shehzad wrote:
> >I would like to start with a couple of very simple questions on 6509
>running
> >Hybrid Code CATOS 6.3.3 and MSFC code 12.1aE5.
> >
> >1. The default behavior of 6509 is QoS disabled,
> > considering a lab scenario, if TOS=7 data is entering FE-port
>3/25-VLAN100
> >and exiting port 2/25-VLAN21 (WS-X6348-RJ-45-48 Port FE), will the TOS
>value
> >be retained ?
>
>Yes, IP Tos and DSCP values are preserved when QoS is disabled.
>
> >2. IF QoS turned on, no QoS attached to any of the VLANs or ports, if a
> >packet with TOS=7 enters and exits the ports/vlans mentioned above, will
>the
> >TOS value be retained ?
>
>No, all packets on ports that are untrusted, (which is the default) will
>have there ToS / DSCP values rewrititten to 0.
>
> >I have a similar scenario setup in my Lab and somehow every packet (I'm
> >sending ICMP TOS=7 packets) is getting stamped to TOS=0 whether I turn QoS
> >ON or OFF.
>
>If you disable QoS it should revert back to not modifying the ToS/DSCP
>value.
>
>
> >* If I turn on QoS, match for ICMP packets and re-stamp to another TOS
>value
> >it works as expected.
>
>After a reboot, with qos disabled does the switch correctly pass the packet
>without changing the ToS/DSCP value?
>
>
>Ian
>
> >I did some search on CCO and found following:
> >
> >Configuring Quality of Service (release 6.3)
> >http://www.cisco.com/univercd/cc/td/doc/product/lan/cat6000/sw_6_3/confg_gd
>/
> >qos.htm
> >QoS Default Configuration
> >Table 41-3 shows the QoS default configuration.
> >Note:
> >With QoS enabled and all other QoS parameters at default values, QoS sets
> >Layer 3 DSCP to zero and Layer 2 CoS to zero in all traffic transmitted
>from
> >the switch.
> >This answers my 1st question,
> >
> >But my problem is even though the QoS is turned off everything is getting
> >stamped with TOS=0,
> >
> >Any comments/experiences ?
> >
> >SH
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