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The AR Directly Connects to a PC, but the Ping Operation Fails

Publication Date:  2015-04-01 Views:  448 Downloads:  0
Issue Description

Figure 1 AR directly connects to a PC

Fault Symptom:
The AR functions as the DHCP server and the PC automatically obtains an IP address, but the AR cannot be pinged from the PC.

Handling Process
1.  Disable the firewall on the PC. Windows 7 is used as an example.

The procedure is as follows:
Choose Control Panel > > System and Security > > Windows Firewall > > Turn Windows Firewall on or off and select Turn off Windows Firewall (not recommended), and click OK.

2.  Then the ping operation succeeds.
Root Cause
Check ARP entries on the AR. The ARP entries are normal. Check the interface configuration. The interface configuration is correct.

Clear the statistics on the interface and ping the PC from the AR. Check statistics on the interface. There are statistics in the outbound direction but no statistics in the inbound direction, indicating that ICMP Request packets are sent normally.

Obtain packets on the PC. The PC can receive ICMP Request packets, but does not send ICMP Reply packets. The preceding phenomenon shows that firewall is enabled on the PC.

When the directly connected PC cannot be pinged, perform the following operations:
  • Check whether the AR hardware interface is damaged. You can replace the AR interface.
  • Check PC settings including the IP address, gateway, and firewall.
  • Check the AR interface configuration. For example, check whether QoS commands are configured on an AR interface to filter ping packets.
First check whether ARP entries are normal and whether the AR learns the MAC address entry of the remote device. Check the statistics on the connected interface or obtain packets to determine ICMP packet receiving and sending.