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I deployed a kolla-openstack and attached floating IP to an instance in it.

Now while I am trying to ping the IP I am getting no response, but when I do ctrl+c it shows 100% loss.enter image description here

Now leaving this aside, if I try to ping an IP which is 100% not present in the network, I am getting a clear enter image description here

I have two questions:

  1. How do I resolve the issue, what could be the most plausible issue?
  2. what is the meaning of ping not responding/not showing output but shows 100% packet loss mean?
Vishwa Mithra Tatta
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1 Answers1

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There are many reasons why ping could fail. 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:

[root@localhost]~# iptables-save
...
[root@localhost]~# iptables -I INPUT 1 -p icmp --icmp-type echo-request -j DROP
[root@localhost]~# ping localhost
PING localhost (127.0.0.1) 56(84) bytes of data.
^C
--- localhost ping statistics ---
5 packets transmitted, 0 received, 100% packet loss, time 4004ms

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:

[root@localhost]~# iptables -p icmp -h | grep host-unreach
   host-unreachable
   TOS-host-unreachable
[root@localhost]~# iptables -D INPUT 1
[root@localhost]~# iptables-save
...
[root@localhost]~# iptables -I INPUT 1 -p icmp --icmp-type echo-request -j REJECT --reject-with icmp-host-unreachable
[root@localhost]~# ping localhost
PING localhost (127.0.0.1) 56(84) bytes of data.
From localhost (127.0.0.1) icmp_seq=1 Destination Host Unreachable
From localhost (127.0.0.1) icmp_seq=2 Destination Host Unreachable
^C
--- localhost ping statistics ---
2 packets transmitted, 0 received, +2 errors, 100% packet loss, time 1000ms

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. "Host unreachable" means a firewall (or any network device anywhere along the route) is rejecting the echo requests with a specific ICMP response type.

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. 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.

thrig
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