[j-nsp] CoS value of return traffic

Danny Vernals danny.vernals at gmail.com
Wed Oct 19 04:01:36 EDT 2011


On Tue, Oct 18, 2011 at 11:14 PM, Ben Dale <bdale at comlinx.com.au> wrote:
> Hi there,
>
> We are experiencing an issue caused by exactly this behaviour (Control traffic from the RE being automatically marked as CoS 6), and I think the current answer regarding changing the value is no.  We are currently getting around it by looping traffic back into the MX80 (using physical ports) in order to strip 802.1p off transit traffic, which is an expensive hack to say the least.
>

I haven't tested this on an MX80 but on a MX960 (both DPC + MPC,
running 10.4 irrc) if you use an egress lo0 firewall filter with a
term with "then dscp #": 802.1p will inherit the value of the 3 most
significant bits of the DSCP you have set.

> When I get some more time in the lab I'll try using lt interfaces to do the same.
>
> Cheers,
>
> Ben
>
> On 18/10/2011, at 9:40 PM, wojtas at wizja.net.pl wrote:
>
>> Hello,
>> Is there a possibility to set the CoS (802.1p) value of return traffic from RE ?
>> I know that You can do it for, at least , DSCP using:
>> set class-of-service host-outbound traffic <dscp-code-point|forwarding-class)

I couldn't say definitively but if I had to guess I'd say this would
have the same effect as setting DSCP via egress firewall filter, i.e.
802.1p would inherit MSB values.

>> Each time I send UDP echo probes to MX80 with different CoS values , the router responds with the same pattern 100(binary). The best workaround in this case would be to set CoS values according to the particular DSCP (which is preserved in this case).
>> Thanks in advance for Your help!
>>
>>
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>
>
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