I can not ping even localhost

[pkotala]

Hallo all experts,
from yesterday I can not send mails from php. Googling internet I found out the problem - ping to localhost does not work - it gets frozen. I tried even

ping 127.0.0.1

without no response as well. When I tried

 ping -c 10 -i 0 localhost

I got standard correct messages.

Can anyone help?

Thank you
Pavel

[manojsamtani]

pls check following:

1) is any firewall running which denying this?
2) output of 'cat /etc/hosts ??
3) output of 'ip addr' ??

--
Manoj

[azpan47]

Check if your loopback interface is up : ifconfig lo

If not bring it up: ifconfig lo up

[pkotala]

Thank you all, still not running (mails are not sent, ping localhost without any response - hangs). Can you please help having the following info?
Thank you

manojsamtani :
- is any firewall running which denying this? - do not know, hot to find it out?
- cat /etc/hosts
# Do not remove the following line, or various programs
# that require network functionality will fail.
127.0.0.1 Centos localhost.localdomain localhost
::1 localhost6.localdomain6 localhost6
- ip addr
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 16436 qdisc noqueue
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
inet 127.0.0.1/8 scope host lo
inet6 ::1/128 scope host
valid_lft forever preferred_lft forever
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast qlen 1000
link/ether 52:54:00:00:05:09 brd ff:ff:ff:ff:ff:ff
inet 31.31.72.70/24 brd 31.31.72.255 scope global eth0
inet6 fe80::5054:ff:fe00:509/64 scope link
valid_lft forever preferred_lft forever
3: sit0: <NOARP> mtu 1480 qdisc noop
link/sit 0.0.0.0 brd 0.0.0.0


azpan47:
- ifconfig lo
lo Link encap:Local Loopback
inet addr:127.0.0.1 Mask:255.0.0.0
inet6 addr: ::1/128 Scope:Host
UP LOOPBACK RUNNING MTU:16436 Metric:1
RX packets:20258764 errors:0 dropped:0 overruns:0 frame:0
TX packets:20258764 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:35624261259 (33.1 GiB) TX bytes:35624261259 (33.1 GiB)

[azpan47]

Check iptables: iptables -L -n

Also do a tcpdump while you ping: tcpdump -i lo

post the output

[pkotala]

Thank you very much:

iptables -L -n
Chain INPUT (policy ACCEPT)
target prot opt source destination
RH-Firewall-1-INPUT all -- 0.0.0.0/0 0.0.0.0/0

Chain FORWARD (policy ACCEPT)
target prot opt source destination
RH-Firewall-1-INPUT all -- 0.0.0.0/0 0.0.0.0/0

Chain OUTPUT (policy ACCEPT)
target prot opt source destination

Chain RH-Firewall-1-INPUT (2 references)
target prot opt source destination
ACCEPT all -- 0.0.0.0/0 0.0.0.0/0
ACCEPT icmp -- 0.0.0.0/0 0.0.0.0/0 icmp type 255
ACCEPT esp -- 0.0.0.0/0 0.0.0.0/0
ACCEPT ah -- 0.0.0.0/0 0.0.0.0/0
ACCEPT udp -- 0.0.0.0/0 224.0.0.251 udp dpt:5353
ACCEPT udp -- 0.0.0.0/0 0.0.0.0/0 udp dpt:631
ACCEPT tcp -- 0.0.0.0/0 0.0.0.0/0 tcp dpt:631
ACCEPT all -- 0.0.0.0/0 0.0.0.0/0 state RELATED,ESTABLISHED
ACCEPT tcp -- 0.0.0.0/0 0.0.0.0/0 state NEW tcp dpt:22
ACCEPT tcp -- 0.0.0.0/0 0.0.0.0/0 state NEW tcp dpt:21
ACCEPT tcp -- 0.0.0.0/0 0.0.0.0/0 state NEW tcp dpt:80
ACCEPT tcp -- 0.0.0.0/0 0.0.0.0/0 state NEW tcp dpt:10000
ACCEPT tcp -- 0.0.0.0/0 0.0.0.0/0 state NEW tcp dpts:21001:21999
REJECT all -- 0.0.0.0/0 0.0.0.0/0 reject-with icmp-host-prohibited

tcpdump -i lo
hangs as well

[manojsamtani]

Can you try to disable for few minutes and test if you are able to ping localhost/127.0.0.1?

And if possible can you post your iptables configuration file or status of "iptables -L"

[pkotala]

manojsamnati:
- "...Can you try to disable for few minutes..." - what to disable? and how?
Chain INPUT (policy ACCEPT)
target prot opt source destination
RH-Firewall-1-INPUT all -- anywhere anywhere

Chain FORWARD (policy ACCEPT)
target prot opt source destination
RH-Firewall-1-INPUT all -- anywhere anywhere

Chain OUTPUT (policy ACCEPT)
target prot opt source destination

Chain RH-Firewall-1-INPUT (2 references)
target prot opt source destination
ACCEPT all -- anywhere anywhere
ACCEPT icmp -- anywhere anywhere icmp any
ACCEPT esp -- anywhere anywhere
ACCEPT ah -- anywhere anywhere
ACCEPT udp -- anywhere 224.0.0.251 udp dpt:mdns
ACCEPT udp -- anywhere anywhere udp dpt:ipp
ACCEPT tcp -- anywhere anywhere tcp dpt:ipp
ACCEPT all -- anywhere anywhere state RELATED,ESTABLISHED
ACCEPT tcp -- anywhere anywhere state NEW tcp dpt:ssh
ACCEPT tcp -- anywhere anywhere state NEW tcp dpt:ftp
ACCEPT tcp -- anywhere anywhere state NEW tcp dpt:http
ACCEPT tcp -- anywhere anywhere state NEW tcp dpt:ndmp
ACCEPT tcp -- anywhere anywhere state NEW tcp dpts:21001:21999
REJECT all -- anywhere anywhere reject-with icmp-host-prohibited

BTW:
Today it was 3rd time that my server memory raised up so that i had to hard restart server. Is it possible to have any virus at unix system (like a windows), or any unwanted code? Could that be the cause of problem?

[manojsamtani]

try to disable firewall (iptables): service iptables stop

then try to ping


and yes this may be the reason of virus...trosens

[pkotala]

thank you,
disable firewall idd not help

Is there any way to find out if there is virus?
If I use server only for standard apache/mysql should firewall settings be stronger in any way? Any example?

Thank you
Pavel