11-15-2009 01:59 PM - edited 03-01-2019 02:15 PM
Hi All,
I'm a bit lost as to why the output drops start increasing reapidly when I start policing the interface.
For example we look after several schools and we police theses schools to 2M, 4M, etc...
If I do not apply the service-policy to the interface, I do not see any output drops. When I apply the service-policy to the interface, the output drops start increasing rapidly.
interface GigabitEthernet0/1
description School Interconnection
mtu 9216
bandwidth 600000
ip address 203.17.98.x 255.255.255.252
ip flow ingress
load-interval 30
media-type rj45
speed 1000
duplex full
no negotiation auto
no clns route-cache
service-policy output POLICE-SCHOOLS
router#sh int g0/1
GigabitEthernet0/1 is up, line protocol is up
Hardware is MV64460 Internal MAC, address is 0023.33bf.e01a (bia 0023.33bf.e01a)
Description: School Interconnection
Internet address is 203.17.98.x/30
MTU 9216 bytes, BW 600000 Kbit, DLY 10 usec,
reliability 255/255, txload 81/255, rxload 7/255
Encapsulation ARPA, loopback not set
Keepalive set (10 sec)
Full Duplex, 1000Mbps, RJ45, media type is RJ45
output flow-control is XON, input flow-control is XON
ARP type: ARPA, ARP Timeout 04:00:00
Last input 00:00:00, output 00:00:00, output hang never
Last clearing of "show interface" counters 00:04:11
Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 1594
Queueing strategy: fifo
Output queue: 0/40 (size/max)
30 second input rate 18571000 bits/sec, 16421 packets/sec
30 second output rate 192800000 bits/sec, 22236 packets/sec
4271641 packets input, 621574470 bytes, 0 no buffer
Received 4 broadcasts (0 IP multicasts)
0 runts, 0 giants, 0 throttles
0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
0 watchdog, 126 multicast, 0 pause input
5911195 packets output, 2295301227 bytes, 0 underruns
0 output errors, 0 collisions, 0 interface resets
0 babbles, 0 late collision, 0 deferred
0 lost carrier, 0 no carrier, 0 PAUSE output
0 output buffer failures, 0 output buffers swapped out
I've tried increasing the hold-queue to 1024 and 2048 but this hasn't stopped the output drops.
The policing looks like this with some schools removed for brevity
policy-map POLICE-SCHOOLS
class CLASS-TCS-200002-CURRIC
police 2000000 375000 750000 conform-action transmit exceed-action transmit violate-action drop
class CLASS-TCS-200002-ADMIN
police 500000 93750 187500 conform-action transmit exceed-action transmit violate-action drop
class CLASS-TCS-200176-ADMIN
police 500000 93750 187500 conform-action transmit exceed-action transmit violate-action drop
class CLASS-TCS-200176-CURRIC
police 2000000 375000 750000 conform-action transmit exceed-action transmit violate-action drop
class CLASS-TCS-200176-DMZ
police 2000000 375000 750000 conform-action transmit exceed-action transmit violate-action drop
.
.
.
.
class class-default
Any ideas as to why this happens and if it's bad or normal behaviour????
Thanks.
Andy
11-15-2009 10:02 PM
Andy,
This is an expected behavior.
When you configure policing, it will regulate the traffic flow at certain rate and will drop excess traffic.
Say, If you have configured policing at 3 Mbps and if you have 4 Mbps of traffic flowing, 1 Mbps of traffic will be dropped.
If you don't want the excess traffic to be dropped, you need shaping to be configured.
Shaping will buffer the excess traffic and will forward at next interval and avoid excess traffic getting dropped to some extend.
If you are an end customer, it is advisable to configure shaping rather than dropping your own traffic.
HTH,
Nagendra
11-16-2009 05:21 PM
Ditto Nagendra's post, but might add: the interface's "Total output drops:" will count policy drops. Showing interface policy map output stats should provide additional details on the policed drops.
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