Ping - possible ping responses
When a host sends out a Ping to another host, the target host either responds successfully, or returns some error code that further explains the failure. There are several common reasons for a ping to fail. Understanding those responses is important in the troubleshooting process.
ICMP is the protocol used by ping and an echo request can have various responses. These responses appear in a particular way depending upon the platform and operating system you are using.
Cisco IOS
On Cisco IOS, you may have any one of the following responses:
| Character | Description |
|---|---|
| ! | Each exclamation point indicates a receipt of a successful reply. |
| . | Each period indicates the network server timed out as it waits for a reply. |
| U | A destination unreachable error PDU was received. |
| Q | Source quench (destination too busy). |
| M | Could not fragment. |
| ? | Unknown packet type. |
| & | Packet lifetime exceeded. |
Windows CMD responses
On a Windows device, you will typically have one of the following responses:
- Unknown host: This response indicates that the hostname or IP address you entered is not recognized or cannot be resolved to an IP address. It suggests that the target host is not reachable or does not exist.
- Destination host unreachable: This response indicates that the destination host is not reachable from your device. It could be due to various reasons, such as a network connectivity issue, incorrect routing, or the target host being down or unreachable.
- General failure error: This response typically indicates a more generic error that occurred during the ping process. It could be due to a variety of reasons, such as a problem with your network adapter, firewall settings, or issues with the network infrastructure. The "General failure" message does not provide specific details about the cause of the failure and may require further troubleshooting to determine the exact issue.
- Request timed out: This response means that the ICMP Echo Request sent by your device did not receive an ICMP Echo Reply within the specified timeout period. It typically indicates that the target host or network did not respond to the ping request. It could be due to various reasons such as network congestion, firewall blocking ICMP traffic, or the target host being down or inaccessible.
Linux command line responses
Typically, the corresponding responses on a Linux device are similar to the following:
- Unknown host: This response indicates that the hostname or IP address you entered is not recognized or cannot be resolved to an IP address. It suggests that the target host is not reachable or does not exist.
- Destination Host Unreachable: This response indicates that the destination host is not reachable from your device. It could be due to various reasons, such as a network connectivity issue, incorrect routing, or the target host being down or unreachable.
- From
: icmp_seq= Destination Host Unreachable: This response indicates that your device received an ICMP Echo Request from the target host but is unable to reach the destination host. It could be due to a network issue or a routing problem. - From
: icmp_seq= Request timed out: This response means that your device did not receive an ICMP Echo Reply from the target host within the specified timeout period. It typically indicates that the target host or network did not respond to the ping request. It could be due to various reasons such as network congestion, firewall blocking ICMP traffic, or the target host being down or inaccessible.