This SF Answer helped me after nerve's answer below:
No network loopback device after security update ubuntu 12.04
Original Question
I've been Google-ing and banging my head against the wall for a couple of hours on this one.
- The server can ping all outside address (Google.com, Yahoo.com,
Microsoft.com, etc). - The server can't ping itself (127.0.0.1 or any static IP address on
this machine) - I can ping the server remotely.
- Pinging a domain name on the server does translate the domain to the correct IP… but the server can't access that IP address
This use to be working up to a week ago and I'm not sure what changed. I found out as I had a cron job that went out to a web page on a server with "wget" to download a report. That report stopped happening.
wget
hangs and I believe it's related to the fact that the server is not allowing connecting to itself.
-
I did play around with
denyhosts
last week and I did try turningdenyhosts
off as well as verify127.0.0.1
is inhosts.allow
and the server IP addresses are not inhosts.deny
and checked all denyhost files in/var/lib/denyhosts
. I couldn't find any of my server's IP address. -
I also checked IPtables and I didn't see any rules there and I did follow some instructions to "turn off" IPTables (set rules to allow) and that had no affect.
-
I checked to make sure ECHO responses are on for ping and I did not find any configuration settings turning it off (and I can ping the server remotely).
-
ifconfig
correctly lists all of my IP address. -
I checked
auth.log
andsysconf
log and couldn't find anything helpful there.
I'm out of ideas of what to try next? Are there any other suggestions or ideas?
update
Per Mark Wagner's comment, the output of sysctl net.ipv4.icmp_echo_ignore_all
is:
net.ipv4.icmp_echo_ignore_all = 0
I'm also checking on the loopback device (lo). I did come across some discussion about that. I'll look into that some more but here's my ifconfig
(masked some of my IP address). I don't see any lo
in there, but perhaps I didn't put the right option in either.
Also, I get the same problem if I try to ping one of the IP address as well, such as ping 66.###.###.##
or if I ping the domain name:
# ping www.mysite.com
PING mysite.com (66.180.###.##) 56(84) bytes of data.
// no response until I kill it
--- mysite.com ping statistics ---
91 packets transmitted, 0 recieved, 100% packet loss, time 90004ms
ifconfig…
venet0 Link encap:UNSPEC HWaddr 00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00
inet addr:127.0.0.1 P-t-P:127.0.0.1 Bcast:0.0.0.0 Mask:255.255.255.255
UP BROADCAST POINTOPOINT RUNNING NOARP MTU:1500 Metric:1
RX packets:129685386 errors:0 dropped:0 overruns:0 frame:0
TX packets:191460906 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:14581051788 (14.5 GB) TX bytes:233758055307 (233.7 GB)
venet0:0 Link encap:UNSPEC HWaddr 00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00
inet addr:66.###.###.## P-t-P:66.###.###.## Bcast:0.0.0.0 Mask:255.255.255.255
UP BROADCAST POINTOPOINT RUNNING NOARP MTU:1500 Metric:1
venet0:1 Link encap:UNSPEC HWaddr 00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00
inet addr:66.###.###.## P-t-P:66.###.###.## Bcast:0.0.0.0 Mask:255.255.255.255
UP BROADCAST POINTOPOINT RUNNING NOARP MTU:1500 Metric:1
venet0:2 Link encap:UNSPEC HWaddr 00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00
inet addr:66.###.###.## P-t-P:66.###.###.## Bcast:0.0.0.0 Mask:255.255.255.255
UP BROADCAST POINTOPOINT RUNNING NOARP MTU:1500 Metric:1
venet0:3 Link encap:UNSPEC HWaddr 00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00
inet addr:66.###.###.## P-t-P:66.###.###.## Bcast:0.0.0.0 Mask:255.255.255.255
UP BROADCAST POINTOPOINT RUNNING NOARP MTU:1500 Metric:1
venet0:4 Link encap:UNSPEC HWaddr 00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00
inet addr:66.###.###.## P-t-P:66.###.###.## Bcast:0.0.0.0 Mask:255.255.255.255
UP BROADCAST POINTOPOINT RUNNING NOARP MTU:1500 Metric:1
venet0:5 Link encap:UNSPEC HWaddr 00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00
inet addr:66.###.###.## P-t-P:66.###.###.## Bcast:0.0.0.0 Mask:255.255.255.255
UP BROADCAST POINTOPOINT RUNNING NOARP MTU:1500 Metric:1
Best Answer
I know you had said that the IP addresses were showing up in
ifconfig
, but is the loop back device (lo) showing up in theifconfig
as well? the behavior you're describing sounds exactly like the behavior that would occur were you to runifdown lo
.