Run the Internet Connections Troubleshooter. This should be done from both the source and destination hosts, and may come to involve anyone who maintains the network systems (routers, firewall, load balancers that can fake network traffic, etc) between the source and destination. If the ping transmit failed issue only shows in the local network group, also restart the local network group. Resolving the issue will involve figuring out the network topology ( traceroute, checking the documentation, etc), using tcpdump or similar packet tracers, reviewing the firewall rules and logs, etc. "Host unreachable" means a firewall (or any network device anywhere along the route) is rejecting the echo requests with a specific ICMP response type. So, 100% packet loss means that the echo requests (or maybe the responses on their way back) are being dropped by a firewall (or any network device) somewhere along the network route between the source and destination. Your second case may be legitimate, but can also be caused by a firewall rule that returns a suitable ICMP response, as simulated on the same test host: iptables -p icmp -h | grep iptables -D INPUT iptables -I INPUT 1 -p icmp -icmp-type echo-request -j REJECT -reject-with ping localhostįrom localhost (127.0.0.1) icmp_seq=1 Destination Host Unreachableįrom localhost (127.0.0.1) icmp_seq=2 Destination Host UnreachableĢ packets transmitted, 0 received, +2 errors, 100% packet loss, time 1000ms This is useful for diagnosing data-dependent problems in a network. PING localhost (127.0.0.1) 56(84) bytes of data.ĥ packets transmitted, 0 received, 100% packet loss, time 4004ms You may specify up to 16 pad bytes to fill out the packet you send. Firewalls are a major source of problems for instance if the ICMP echo requests (what ping sends) are simply dropped by a firewall (here iptables on a Linux test virt) then that produces your first case of 100% packet loss: iptables -I INPUT 1 -p icmp -icmp-type echo-request -j ping localhost There are many reasons why ping could fail. PING(8) FreeBSD System Managers Manual PING(8) NAME ping - send ICMP or ICMPv6.
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