Hostname lookup (ping) hangs indefinitely
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Normally if I try pinging an address it will either do so promptly or state that the host is unknown. On one machine however, it seems that trying to ping an unknown host will cause it to hang forever (greater than 15 minutes).
This seems to causing problem in the boot process, hanging when trying to start sendmail services and so on.
Booting in single user mode, the only time ping responds is when pinging one of the hosts listed in /etc/hosts. Otherwise it will hang.
On the other hand, nslookup does seem to timeout after approx. 15 seconds.
ETA This seems to only happen in Single user mode. Once booted up normally (although had to disable SMB and sendmail services to do so) ping now times out if given an invalid name (like 'cabbage')
The 'host' command seems to return the following regardless if given a valid hostname or not;
(hostname).(domain name) mail is handled by 5 smtp01.(company domain name).
(hostname).(domain name) mail is handled by 9 cinsmtp01.(company domain name).
(hostname).(domain name) mail is handled by 9 alpsmtp01.(company domain name).
IIRC it was doing this in both the single boot mode and when booted normally and wasn't hanging. I'll confirm if I get a chance to reboot the machine again.
This is the only CentOS box on our local network - all others are Windows machines so can't really compare against a working machine. But below is a result of grep hosts /etc/nsswitch.conf
#hosts: db files nisplus nis dns
hosts: db files wins nisplus nis dns
The resolv.conf has a number of nameserver entries in it, some of which may not be valid anymore, I'll investigate further and report back.
centos dns ping
asked Oct 26 '16 at 16:01
MJF
12315
bumped to the homepage by Community♦ yesterday
This question has answers that may be good or bad; the system has marked it active so that they can be reviewed.
add a comment |
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1
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Normally if I try pinging an address it will either do so promptly or state that the host is unknown. On one machine however, it seems that trying to ping an unknown host will cause it to hang forever (greater than 15 minutes).
This seems to causing problem in the boot process, hanging when trying to start sendmail services and so on.
Booting in single user mode, the only time ping responds is when pinging one of the hosts listed in /etc/hosts. Otherwise it will hang.
On the other hand, nslookup does seem to timeout after approx. 15 seconds.
ETA This seems to only happen in Single user mode. Once booted up normally (although had to disable SMB and sendmail services to do so) ping now times out if given an invalid name (like 'cabbage')
The 'host' command seems to return the following regardless if given a valid hostname or not;
(hostname).(domain name) mail is handled by 5 smtp01.(company domain name).
(hostname).(domain name) mail is handled by 9 cinsmtp01.(company domain name).
(hostname).(domain name) mail is handled by 9 alpsmtp01.(company domain name).
IIRC it was doing this in both the single boot mode and when booted normally and wasn't hanging. I'll confirm if I get a chance to reboot the machine again.
This is the only CentOS box on our local network - all others are Windows machines so can't really compare against a working machine. But below is a result of grep hosts /etc/nsswitch.conf
#hosts: db files nisplus nis dns
hosts: db files wins nisplus nis dns
The resolv.conf has a number of nameserver entries in it, some of which may not be valid anymore, I'll investigate further and report back.
centos dns ping
asked Oct 26 '16 at 16:01
MJF
12315
bumped to the homepage by Community♦ yesterday
This question has answers that may be good or bad; the system has marked it active so that they can be reviewed.
For an example target host name ofcabbage, what doeshost cabbagereturn in your situation? Does it return or hang? Please also add output ofgrep hosts /etc/nsswitch.confandcat /etc/resolv.confto your question. And identify to us whether these match similar results from a working server.
– roaima
Oct 26 '16 at 17:21
add a comment |
up vote
1
down vote
favorite
up vote
1
down vote
favorite
Normally if I try pinging an address it will either do so promptly or state that the host is unknown. On one machine however, it seems that trying to ping an unknown host will cause it to hang forever (greater than 15 minutes).
This seems to causing problem in the boot process, hanging when trying to start sendmail services and so on.
Booting in single user mode, the only time ping responds is when pinging one of the hosts listed in /etc/hosts. Otherwise it will hang.
On the other hand, nslookup does seem to timeout after approx. 15 seconds.
ETA This seems to only happen in Single user mode. Once booted up normally (although had to disable SMB and sendmail services to do so) ping now times out if given an invalid name (like 'cabbage')
The 'host' command seems to return the following regardless if given a valid hostname or not;
(hostname).(domain name) mail is handled by 5 smtp01.(company domain name).
(hostname).(domain name) mail is handled by 9 cinsmtp01.(company domain name).
(hostname).(domain name) mail is handled by 9 alpsmtp01.(company domain name).
IIRC it was doing this in both the single boot mode and when booted normally and wasn't hanging. I'll confirm if I get a chance to reboot the machine again.
This is the only CentOS box on our local network - all others are Windows machines so can't really compare against a working machine. But below is a result of grep hosts /etc/nsswitch.conf
#hosts: db files nisplus nis dns
hosts: db files wins nisplus nis dns
The resolv.conf has a number of nameserver entries in it, some of which may not be valid anymore, I'll investigate further and report back.
centos dns ping
asked Oct 26 '16 at 16:01
MJF
12315
Normally if I try pinging an address it will either do so promptly or state that the host is unknown. On one machine however, it seems that trying to ping an unknown host will cause it to hang forever (greater than 15 minutes).
This seems to causing problem in the boot process, hanging when trying to start sendmail services and so on.
Booting in single user mode, the only time ping responds is when pinging one of the hosts listed in /etc/hosts. Otherwise it will hang.
On the other hand, nslookup does seem to timeout after approx. 15 seconds.
ETA This seems to only happen in Single user mode. Once booted up normally (although had to disable SMB and sendmail services to do so) ping now times out if given an invalid name (like 'cabbage')
The 'host' command seems to return the following regardless if given a valid hostname or not;
(hostname).(domain name) mail is handled by 5 smtp01.(company domain name).
(hostname).(domain name) mail is handled by 9 cinsmtp01.(company domain name).
(hostname).(domain name) mail is handled by 9 alpsmtp01.(company domain name).
IIRC it was doing this in both the single boot mode and when booted normally and wasn't hanging. I'll confirm if I get a chance to reboot the machine again.
This is the only CentOS box on our local network - all others are Windows machines so can't really compare against a working machine. But below is a result of grep hosts /etc/nsswitch.conf
#hosts: db files nisplus nis dns
hosts: db files wins nisplus nis dns
The resolv.conf has a number of nameserver entries in it, some of which may not be valid anymore, I'll investigate further and report back.
centos dns ping
centos dns ping
asked Oct 26 '16 at 16:01
MJF
12315
asked Oct 26 '16 at 16:01
MJF
12315
edited Oct 27 '16 at 11:03
asked Oct 26 '16 at 16:01
MJF
12315
asked Oct 26 '16 at 16:01
MJF
12315
asked Oct 26 '16 at 16:01
MJF
12315
12315
bumped to the homepage by Community♦ yesterday
This question has answers that may be good or bad; the system has marked it active so that they can be reviewed.
bumped to the homepage by Community♦ yesterday
This question has answers that may be good or bad; the system has marked it active so that they can be reviewed.
For an example target host name ofcabbage, what doeshost cabbagereturn in your situation? Does it return or hang? Please also add output ofgrep hosts /etc/nsswitch.confandcat /etc/resolv.confto your question. And identify to us whether these match similar results from a working server.
– roaima
Oct 26 '16 at 17:21
add a comment |
For an example target host name ofcabbage, what doeshost cabbagereturn in your situation? Does it return or hang? Please also add output ofgrep hosts /etc/nsswitch.confandcat /etc/resolv.confto your question. And identify to us whether these match similar results from a working server.
– roaima
Oct 26 '16 at 17:21
For an example target host name of
cabbage, what does host cabbage return in your situation? Does it return or hang? Please also add output of grep hosts /etc/nsswitch.conf and cat /etc/resolv.conf to your question. And identify to us whether these match similar results from a working server.– roaima
Oct 26 '16 at 17:21
For an example target host name of
cabbage, what does host cabbage return in your situation? Does it return or hang? Please also add output of grep hosts /etc/nsswitch.conf and cat /etc/resolv.conf to your question. And identify to us whether these match similar results from a working server.– roaima
Oct 26 '16 at 17:21
add a comment |
1 Answer
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If you're truly just doing it for the purpose of a hostname lookup, use the host command instead. That's its purpose.
Firewalls are often configured to drop ICMP packets. If this is the case, your ping will never get a reply (even if the host is up), and will just keep sending packets in to a black hole that never responds.
host will usually respond quickly with an IP (or not) whether the remote host exists or not, or is configured to drop packets or not. And if the command takes to long for your tastes, you can configure the timeout with the -W option.
answered Oct 26 '16 at 19:01
Dale Anderson
31118
even if ICMP are blocked, the resolution is supposed to happen. The OP is having DNS configuration problems.
– Rui F Ribeiro
Feb 10 at 10:07
add a comment |
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1 Answer
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up vote
0
down vote
If you're truly just doing it for the purpose of a hostname lookup, use the host command instead. That's its purpose.
Firewalls are often configured to drop ICMP packets. If this is the case, your ping will never get a reply (even if the host is up), and will just keep sending packets in to a black hole that never responds.
host will usually respond quickly with an IP (or not) whether the remote host exists or not, or is configured to drop packets or not. And if the command takes to long for your tastes, you can configure the timeout with the -W option.
answered Oct 26 '16 at 19:01
Dale Anderson
31118
even if ICMP are blocked, the resolution is supposed to happen. The OP is having DNS configuration problems.
– Rui F Ribeiro
Feb 10 at 10:07
add a comment |
up vote
0
down vote
If you're truly just doing it for the purpose of a hostname lookup, use the host command instead. That's its purpose.
Firewalls are often configured to drop ICMP packets. If this is the case, your ping will never get a reply (even if the host is up), and will just keep sending packets in to a black hole that never responds.
host will usually respond quickly with an IP (or not) whether the remote host exists or not, or is configured to drop packets or not. And if the command takes to long for your tastes, you can configure the timeout with the -W option.
answered Oct 26 '16 at 19:01
Dale Anderson
31118
even if ICMP are blocked, the resolution is supposed to happen. The OP is having DNS configuration problems.
– Rui F Ribeiro
Feb 10 at 10:07
add a comment |
up vote
0
down vote
up vote
0
down vote
If you're truly just doing it for the purpose of a hostname lookup, use the host command instead. That's its purpose.
Firewalls are often configured to drop ICMP packets. If this is the case, your ping will never get a reply (even if the host is up), and will just keep sending packets in to a black hole that never responds.
host will usually respond quickly with an IP (or not) whether the remote host exists or not, or is configured to drop packets or not. And if the command takes to long for your tastes, you can configure the timeout with the -W option.
answered Oct 26 '16 at 19:01
Dale Anderson
31118
If you're truly just doing it for the purpose of a hostname lookup, use the host command instead. That's its purpose.
Firewalls are often configured to drop ICMP packets. If this is the case, your ping will never get a reply (even if the host is up), and will just keep sending packets in to a black hole that never responds.
host will usually respond quickly with an IP (or not) whether the remote host exists or not, or is configured to drop packets or not. And if the command takes to long for your tastes, you can configure the timeout with the -W option.
answered Oct 26 '16 at 19:01
Dale Anderson
31118
answered Oct 26 '16 at 19:01
Dale Anderson
31118
answered Oct 26 '16 at 19:01
Dale Anderson
31118
answered Oct 26 '16 at 19:01
Dale Anderson
31118
31118
even if ICMP are blocked, the resolution is supposed to happen. The OP is having DNS configuration problems.
– Rui F Ribeiro
Feb 10 at 10:07
add a comment |
even if ICMP are blocked, the resolution is supposed to happen. The OP is having DNS configuration problems.
– Rui F Ribeiro
Feb 10 at 10:07
even if ICMP are blocked, the resolution is supposed to happen. The OP is having DNS configuration problems.
– Rui F Ribeiro
Feb 10 at 10:07
even if ICMP are blocked, the resolution is supposed to happen. The OP is having DNS configuration problems.
– Rui F Ribeiro
Feb 10 at 10:07
add a comment |
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For an example target host name of
cabbage, what doeshost cabbagereturn in your situation? Does it return or hang? Please also add output ofgrep hosts /etc/nsswitch.confandcat /etc/resolv.confto your question. And identify to us whether these match similar results from a working server.– roaima
Oct 26 '16 at 17:21