Marking and reserving bandwidth

   CatCat3640(config)# policy-map switchover
   CatCat3640(config-pmap)# class switchover-traffic
   CatCat3640(config-pmap-c)# bandwidth 1024
   CatCat3640(config-pmap-c)# set dscp af31
   CatCat3640(config-pmap-c)# exit
   CatCat3640(config-pmap)# class class-default
   CatCat3640(config-pmap-c)# fair-queue
   CatCat3640(config-pmap-c)# random-detect
   CatCat3640(config)# int serial 1/0
   CatCat3640(config-if)# service-policy output switchover
   CatCat3640# show policy-map interface serial 1/0 output

In this example, a policy map is created and the switchover-traffic class is configured so that traffic is marked and 1 megabit of bandwidth is reserved for the link. The policy is confirmed by using the show command:

   Cat3640# show policy-map interface serial 1/0 output
    Serial1/0
     Service-policy output: switchover
       Class-map: Switchover (match-all)
         350028 packets, 71328923 
 
 
 bytes
         5 minute offered 
 
 
 rate 90000 bps, drop rate 0 bps
         Match: access-group 
 
 
 101
         Queueing 
           Output 
 
 
 Queue: Conversation 265
           Bandwidth 
 
 
 1024 (kbps) Max Threshold 64 (packets)
           (pkts 
 
 
 matched/bytes matched) 30742/45374387
           (depth/total 
 
 
 drops/no-buffer drops) 0/0/0
         QoS Set
           dscp 
 
 
 af31
             Packets 
 
 
 marked 350028
       Class-map: class-default (match-any)
         148854 packets, 16748633 
 
 
 bytes
         5 minute offered 
 
 
 rate 0 bps, drop rate 0 bps
         Match: any
        
    Queueing
           Flow 
 
 
 Based Fair Queueing
           Maximum 
 
 
 Number of Hashed Queues 256
           (total 
 
 
 queued/total drops/no-buffer drops) 0/0/0
            exponential 
 
 
 weight: 9
     class    Transmitted      Random 
 
 
 drop      Tail drop    Minimum 
 
 
 Maximum  Mark
              pkts/bytes 
       pkts/bytes 
 
       pkts/bytes    thresh 
 
 
  thresh  prob
         0  148855/16748938 
        0/0              0/0 
           20      40 
  1/10 
 
 
         1       0/0 
               0/0 
              0/0 
           22      40 
  1/10
         2       0/0 
               0/0 
              0/0 
           24      40 
  1/10
         3       0/0 
               0/0 
              0/0 
           26      40 
  1/10
         4       0/0 
               0/0 
              0/0 
           28      40 
  1/10
         5       0/0 
               0/0 
              0/0 
           30      40 
  1/10
         6       0/0 
               0/0 
              0/0 
           32      40 
  1/10
         7       0/0 
               0/0 
              0/0 
           34      40 
  1/10
      rsvp       0/0 
               0/0 
              0/0 
           36      40 
  1/10

You can use a tool such as Wire Shark to examine the packets that pass through the router to ensure that the policy is working correctly. In the following example, the packets are marked with AF31 priority.