PC Download Rate Is Slow

Publication Date:  2015-04-01 Views:  355 Downloads:  0
Issue Description
Networking:



Fault Symptom:

The PC download rate is very slow and different from the actual bandwidth.

The configuration of the AR is as follows:

#
interface Ethernet0/0
ip address 60.175.166.100 255.255.255.0
nat outbound 2000 address-group 0
nat server protocol tcp global 60.172.141.118 8080 inside 192.168.2.9 8080
nat server protocol tcp global 60.172.141.118 8000 inside 192.168.2.9 8000
nat server protocol tcp global 60.172.141.118 8001 inside 192.168.2.171 8001
nat server protocol tcp global 60.172.141.118 81 inside 192.168.2.171 81
nat server protocol tcp global 60.175.166.100 www inside 192.168.2.9 www
#
interface Ethernet0/1
speed 100
duplex full
description siwang
ip address 172.0.0.1 255.255.255.0
Handling Process
Check whether traffic shaping and rate limiting are configured on the uplink and downlink interfaces of the AR. There are no traffic shaping and rate limiting configurations.

Run the display this interface command in the interface view to check statistics on the physical interface connecting the AR and modem.

The following information shows that there are many packets with CRC errors on the local interface, which may cause the slow PC download.

Input: 1355029 packets, 1393107734 bytes, 1355029 buffers
           4537 broadcasts, 72 multicasts, 0 pauses
           81792 errors, 4660 runts, 0 giants
           77132 crc, 0 align errors, 0 overruns
           0 dribbles, 0 drops, 0 no buffersDisable auto-negotiation and manually configure the duplex mode and rate. The packets with CRC errors still increase.


Connect the PC to the modem. The download rate is still slow. Check the modem. The indicator of the model flashes abnormally. After the modem is replaced, the download rate is normal.

Suggestions
Use the following troubleshooting methods to locate such a fault:
  • Check whether the indicator of the modem flashes abnormally. If so, replace the modem. Most of such problems can be solved by modem replacement.
  • Check whether traffic shaping and rate limiting are configured on the uplink or downlink interface of the AR. If traffic shaping and rate limiting are configured on the uplink or downlink interface, delete the traffic shaping and rate limiting configuration.
  • Run the display this interface command to check statistics on the physical interface connecting the AR and modem. Check whether there are statistics on packets with CRC errors. If there are statistics on packets with CRC errors, disable auto-negotiation and manually configure the duplex mode and rate.
  • If PPPoE dialup is used on the AR, run the tcp adjust 1200 command on the dialer interface.
  • If the fault persists, directly connect the PC to the model and check whether download is normal. Then determine whether rate limiting is configured on the firewall.

END