QOS Conundrum - bandwidth, shape average or shape peak?

From: Mark Turner (markturner101@gmail.com)
Date: Sun Jan 06 2008 - 21:06:53 ARST


Hello,

I am trying to solve the below question. I have included the
configuration that I believe will work. I am just unclear as to the
best method to rate limit to a specific value if rate limiting and
policing are specifically forbidden. I have narrowed it down to the
shape average, shape peak or bandwidth statement but cant decide which
to use.

"Configure R2 so that traffic marked with the precedence value 3
AND/OR traffic from VLAN_C (1.1.1.1) to VLAN_BB2 (2.2.2.2) is
guaranteed minimum of 128K of bandwidth when sent out of interface
fast 0/0. If congestion occurs assure this traffic is randomly
dropped. Also make sure that traffic marked with prec value 2 is rate
limited to 128K. Do not use rate-limiting or policing."

Access-list 100 permit ip 1.1.1.0 0.0.0.255 2.2.2.0 0.0.0.255

class-map match-any prec3
  match ip precedence 3
  match access-group name prec3
!
class-map match-any PREC2
  match ip precedence 2
!
policy-map cisco
  class VLANC-TO-VLAN_BB2
   bandwidth 128
   random-detect
  class PREC2
  shape average 128000 -> my best guess

OR
 class PREC2
  shape peak 128000

OR
 class PREC2
  bandwidth 128



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