QoS

I have a question about the solution a QoS excersise

          Requirement - Router originated telnet traffic should have a dscp
of EF. Give the neccessary config.

         Restrictions:
         Do this without using any interface commands
         Do not use the command -> ip telnet tos xxx

The solution to this is:
        !
         access-list 101 permit tcp any any eq telnet
        !
        route-map telnet permit 10
        match ip address 101
        set ip precedence 5
        set ip tos 12
        !
        ip local policy route-map telnet

 Can you explain the TOS bit numbering for me? If i check the configuration
you are able to select tos 0-15.

What I thought is that TOS is 128 bits (8 caracters). Left 3 are Precedence
and left 6 are DSCP
precedence 5 is 101 00000
DSCP ef is 101110 00
So if you need to add 00011000 to 1010000 to make 10111000
if I calculate 00011000 it is 24
What I understood from a previous post is that a 0 is appended and prepended
so this maken 01011100. But why is in this case the 0 prepended in front of
the bits. Normaly DSCP are the left six bits. Now for all of a sudden in a
route-map the DSCP bits are 7,6,5,4,3,2
Normaly when you calculate Precedence or DSCP in TOS yoi take bits 8,7,6 for
precedence and 8,7,6,5,4,3 for DSCP
Precedence 5 = TOS 160

Blogs and organic groups at http://www.ccie.net
Received on Wed May 12 2010 - 20:16:26 ART