Ping Utility in pfSense

The Ping Utility Explained

Ping

Using the Ping utility in pfSense.

Ping is a computer network administration utility used to test the reachability of a host on an IP network and to measure the round-trip time for messages sent from the originating host to a destination host. It operates by sending Internet Control Message Protocol (ICMP) echo request packets to the target host and waiting for an ICMP response. In the process it measures the time from transmission to reception and records any packet loss.


RFC 1122, which defines communication layer requirements for Internet hosts, says the following about Echo Requests and Replies:

Every host MUST implement an ICMP Echo server function that receives Echo Requests and sends corresponding Echo Replies. A host SHOULD also implement an application-layer interface for sending an Echo Request and receiving an Echo Reply, for diagnostic purposes.

An ICMP Echo Request destined to an IP broadcast or IP multicast address MAY be silently discarded.

DISCUSSION:

This neutral provision results from a passionate debate between those who feel that ICMP Echo to a broadcast address provides a valuable diagnostic capability and those who feel that misuse of this feature can too easily create packet storms.

The echo request (“ping”) is an ICMP message whose data is to be received back in an echo reply (“pong”). The host must respond to all echo requests with an echo reply containing the exact data received in the request message. The echo reply is an ICMP message generated in response to an echo request, and is mandatory for all hosts and routers.


Using the Ping Utility in pfSense

To use the pfSense ping utility, first navigate to Diagnostics -> Ping. Then at “Host”, set the host to the IP address or hostname of the host we are trying to ping. At “Interface”, choose the interface from which to initiate the ping (WAN for remote hosts, LAN for local hosts). At “Count”, use the dropdown set the number of ping requests (anywhere from 1 to 10; the default of 3 is usually sufficient). Then press the “Ping” button to invoke the utility. Sending out ICMP echo requests is often a useful diagnostic tool; however, multi-WAN is not supported with this utility.

External Links:

Ping at Wikipedia

RFC 1122 (which mandates that Internet hosts reply to ICMP echo requests)

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