Cisco

Generate DSCP marked pings

moonie

Jun 22, 2013 • 1 min read

Today it was useful to confirm a switch was passing DSCP marked packets as expected and handling 'ef' marked packets.

To do this on a cisco switch we can use the extended ping feature and set the Type of Service (ToS) to a decimal value that is equivalent to the DSCP value wanted. The table below shows the ToS value to enter to get the DSCP marking needed.

TOS (decimal)	DSCP Class
0	be
32	cs1
40	af11
48	af12
56	af13
64	cs2
72	af21
80	af22
88	af23
96	cs3
104	af31
112	af32
120	af33
128	cs4
136	af41
144	af42
152	af43
160	cs5
184	ef
192	cs6
224	-

So for example if we want to generate EF marked packets we can use the value of 184 for ToS when configuring the extended ping. Obviously any other marking like af43 = 152 can easily be used too.

On a Cisco switch extended ping example below:

Moons-Router#ping
Protocol [ip]: 
Target IP address: 8.8.8.8
Repeat count [5]: 100
Datagram size [100]: 
Timeout in seconds [2]: 
Extended commands [n]: y
Source address or interface: 
Type of service [0]: 184 <---------THIS SETS THE QOS MARKING
Set DF bit in IP header? [no]: 
Validate reply data? [no]: 
Data pattern [0xABCD]: rotate
Loose, Strict, Record, Timestamp, Verbose[none]: 
Sweep range of sizes [n]: 
Type escape sequence to abort.
Sending 100, 100-byte ICMP Echos to 8.8.8.8, timeout is 2 seconds:
Packet has rotating data pattern starting with 0x0000
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
Success rate is 100 percent (100/100), round-trip min/avg/max = 60/63/64 ms

Nice hacky way to generate ef marked traffic for testing :)

More info about DSCP values in relation to other values can be found [HERE].

m00nie

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