Lab Tip: Remembering IP Precedence Values

I’ve never bothered to memorize the Cisco descriptions of IP Precedence values (i.e. IP Precedence 4 is “flash-override”).  I’ve hit a couple of labs which ask you to manipulate traffic based on these descriptions.  For instance:

“Drop all flash traffic coming into r1 from VLAN 6.”

Some commands such as ‘random detect precedence’ only use the 0 – 7 values: 

r1(config-if)#random-detect precedence ?
  <0-7>  IP precedence
  rsvp   rsvp traffic

You could look this up in the DOC CD, but there’s a quick and dirty way to do this on the command line.

1) Create a class-map.
2) Type ‘match ip precedence ?’ to see the context-sensitive help.  This will give you a list of the IP Precedence values along with their descriptions.
3) Get what you need and remember to delete the class-map.

Rack13R6(config)#class-map FAKE
Rack13R6(config-cmap)#match ip precedence ?
  <0-7>           Enter up to 4 precedence values separated by white-spaces
  critical        Match packets with critical precedence (5)
  flash           Match packets with flash precedence (3)
  flash-override  Match packets with flash override precedence (4)
  immediate       Match packets with immediate precedence (2)
  internet        Match packets with internetwork control precedence (6)
  network         Match packets with network control precedence (7)
  priority        Match packets with priority precedence (1)
  routine         Match packets with routine precedence (0)
Rack13R6(config-cmap)#exit
Rack13R6(config)#no class-map FAKE