How to locate the ping failure

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When the ping operation fails, locate the fault based on the following troubleshooting roadmap:
1. Check whether the AR interface is Up and whether the IP address is configured correctly.
Command: display interface brief and display ip interface [ < interface-type > < interface-number > ]
2. If a Layer 2 interface is used, check whether STP is running on the AR and check whether the physical interface where ping packets pass is blocked.
Command: display stp [ instance < instance-id > ] [ interface < interface-type > < interface-number > ] [ brief ]
3. Check whether routes are reachable: If routes are unreachable, troubleshoot the fault.
Command: display ip routing-table
4. Check whether policies are configured on local and remote devices. If the remote device is a firewall, check whether the remote interface is added to a zone and whether the inter-zone rule is enabled.
5. Check whether ARP entries of the direct route are learned correctly. If ARP entries cannot be learned, check whether strict ARP learning is enabled. Disable strict ARP learning and try again. If the fault persists, perform the ping operation on one device and check whether ARP request packets are sent out from the interface and whether the remote device sends ARP reply packets based on ARP packet statistics.
Commands: display arp and display arp learning strict
6. If there is no preceding problem, collect statistics on ICMP packets, determine the position where packets are lost and locate the packet loss point.

Other related questions:
How do I locate the 3G dialup failure on an AR
Run the display cellular interface-number network command to check the value of the Current Service Status field. - When the value of the Current Service Status field is Service Available, the 3G service is available. Check the following configurations: 1. Check whether the dialer number is configured correctly. 2. If the 3G interface is connected to the WCDMA network or a network that is compatible with the WCDMA network, check whether the APN is configured correctly. 3. Check whether the authentication mode, user name, and password are configured correctly. 4. Check whether the dialer ACL is configured correctly. 5. Check whether static routes are configured correctly. - When the value of the Current Service Status field is No Service, the 3G service is unavailable. Check the following configurations: 1. If the 3G interface is connected to the WCDMA network or a network that is compatible with the WCDMA network, run the display cellular interface-number network command to check values of the Mobile Country Code (MCC), Mobile Network Code (MNC), and Mobile Operator Information fields and check whether the PLMN selected by the 3G modem is consistent with that of the carrier. If the 3G interface is connected to the CDMA2000 network or a network that is compatible with the CDMA2000 network, you can skip this step. 2. Run the display cellular interface-number radio command to check the value of the Current RSSI field. 3. Check whether the 3G data card is supported by the AR. 4. Run the display cellular interface-number radio command to check the value of the SIM Status field and check whether the SIM, USIM, or UIM card status is normal. 5. Check whether the 3G hardware (including the 3G data card/3G interface card/3G model), SIM/USIM/UIM card, or 3G antenna is damaged, not properly installed, or not fastened. 6. Check whether the angle of the 3G antennas is proper. 7. Check whether 3G/2G services are enabled on the SIM, USIM, or UIM card and whether the users owe fees. 8. Run the display cellular interface-number radio command to check the value of the PIN Status field.

How do I locate VAP creation failures
To locate VAP creation failure on a WLAN device, perform the following steps: For an AC: V200R005 and earlier 1. Check whether the AP exists. 2. Check whether the VAPs of the AP are fully configured. 3. Check whether the radio interface is bound to a radio profile. 4. Check whether the service set is configured correctly and bound to the radio interface. 5. Check whether the configuration is committed. 6. Check whether the AP works properly and whether the configuration is delivered successfully. V200R006 and later 1. Check whether the AP exists. 2. Check whether the VAPs of the AP are fully configured. 3. Check whether the radio interface is bound to a radio profile. 4. Check whether the VAP profile is configured correctly and bound to the AP or an AP group. 5. Check whether the AP works properly and whether the configuration is delivered successfully. For a Fat AP: 1. Check whether the VAPs of the AP are fully configured. 2. Check whether the radio interface is bound to a radio profile. 3. Check whether the service set is configured correctly and bound to the radio interface. For an S series switch serving as the AC 1. Check whether the AP exists. 2. Check whether the VAPs of the AP are fully configured. 3. Check whether the radio interface is bound to a radio profile. 4. Check whether the service set is configured correctly and bound to the radio interface. 5. Check whether the configuration is committed. 6. Check whether the AP works properly and whether the configuration is delivered successfully.

How to locate the cause of a mirroring failure on an S series switch
If mirroring fails on an S series switch (except the S1700), locate the cause by referring to Fault Locating Guide-Software Troubleshooting-Mirroring. If you have no access permission, contact Huawei technical support personnel.

Possible causes for a failure to ping an IPv6 address
In V100R002 and later versions, the IPv6 address of a device fails to be pinged due to the following possible causes: l. The physical state or protocol state of the interface is Down. You can run the display ipv6 interface interface-type interface-number command in any view to check the physical state and protocol state of an interface. 2. The switch fails to learn ND entries of the peer device. You can run the display ipv6 neighbors command in any view to check information about ND entries. 3. The link transmission delay is too long. The source device does not receive any Response packet from the destination device within the waiting time, and the ping operation fails. You can run the ping ipv6 -t timeout destination-ipv6-address command in any view to set “-t&rdquo to increase the timeout interval for waiting for Response packets.

How to quickly locate a failure to set up a tunnel between the LAC and LNS
During L2TP configuration, if the LAC cannot set up a tunnel with the LNS, perform the following operations to locate the fault quickly.
1. Run the start l2tp command on the LAC to check whether there is a reachable route to the LNS. If the route is unreachable, configure a reachable route to the LNS.
2. Check the L2TP configuration on the LNS and delete the remote specified in the allow l2tp command. If an L2TP tunnel can be established successfully, the cause is that the tunnel name on the LAC is incorrect or the tunnel name specified by the LNS is incorrect. Select either of the following solutions.
 - Run the tunnel name command on the LAC to configure the local tunnel name as the value of remote in the allow 12tp command on the LNS.
 -Run the allow l2tp command on the LNS to change the remote parameter so that the tunnel name is consistent with that configured on the LAC. If the local tunnel name is not configured using the tunnel name command on the LAC, the value of the remote parameter is the device name of the LAC.

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