What does the command ping 1:: mean?

The ping 1:: command is used to diagnose network reachability of a node with the IPv6 address 1::.

This is a special IPv6 address known as the unspecified address. It is similar to the IPv4 address 0.0.0.0.

1:: is a shortened notation for 0001:0000:0000:0000:0000:0000:0000:0000.

What the ping command does:

Sends ICMPv6 Echo Request packets to the specified address and waits for ICMPv6 Echo Reply packets. It measures response time and packet loss percentage.

Features when pinging 1:::

• Purpose: This address is not assigned to a specific interface or node. It is used in routing contexts or to indicate that the source address is unknown (e.g., during interface initialization).
• Result: Pinging 1:: usually does not result in a response. The system receiving the request to this address will not process it as intended for itself and will not send an Echo Reply. Most often, you will see messages indicating the node is unreachable or a timeout.

Example output (may vary slightly depending on OS):

ping 1::
// PING 1::(1::) 56 data bytes
// from ::1 icmp_seq=1 Destination unreachable: Administratively prohibited
// ... or ...
// PING 1:: (1::) 56(116) bytes of data.
// --- 1:: ping statistics ---
// 4 packets transmitted, 0 received, 100% packet loss, time 3015ms

Thus, the ping 1:: command checks network routing and reachability in IPv6, but the expected result is unreachability, since the address 1:: is not intended for direct interaction.