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Webcast-Catalyst9k
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ip-precedence AND . dscp-bit based queuing at the same time

hi,

i do queueing based on ip-prec bit.

i mark traffic with ip-prec bit from 0 to 5 and then queueing - everything is fine.

now i need a new "coulor" for a packet, but i don´t want to use

ip-prec=6 or 7 because this is reserved for network contol.

can i use the dscp-value in the ip-header AND the "old" ip-prec value together.

i mean so that the "old" trafffic i had tille now is queued as before and the

for "new" traffic i use a dscp value and my queuing gets a new class.

this new class matches on the dscp-value for the "new" traffic.

all other traffic is marked and queued with the old ip-prec values .

thanks for answer !

1 REPLY
Silver

Re: ip-precedence AND . dscp-bit based queuing at the same time

It's Ok to mix dscp and precedence if you're careful. Remember that Precedence only looks at the first three bits of eight in TOS field while DSCP looks at six bits. (from the left)

This means that Precedence 0=DSCP 0-7. Precedence 1=DSCP 8-15. etc... It also means that DSCP=8 will match Precedence=1. As will DSCP=9 and DSCP=10... all the way up to DSCP 15 will match Precedence=1 .

Therefore, you must call the class-maps defining your DSCP values before the class-maps calling Precedence values in your policy-maps. The policy-map evaluates the class-maps in order. Also, don't define DSCP values for traffic that coincide with precedence values. In otherwords, don't use values 0,8,16,24,32,40,48, or 56 for any DSCP definitions.

-Shannon

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