Login or Register to Ask a Question and Join Our Community

Sponsored Content
Full Discussion: Interpretation of Ping behaviour
Top Forums UNIX for Advanced & Expert Users Interpretation of Ping behaviour Post 302921802 by jim mcnamara on Monday 20th of October 2014 11:21:34 AM
Old 10-20-2014
/etc/resolv.conf just enumerates the order and names of dns servers to check. You
may need to modify that. We use several dns servers in out network - two infoblox appliances and one windows domain controller.

As Made_in_Germany said, /etc/nsswitch.conf controls where to look in general.

Is your cache name service daemon running? Turn on dns caching.

Code:
/fmd> svcs /system/name-service-cache
STATE          STIME    FMRI
online         Oct_17   svc:/system/name-service-cache:default

Should say 'online'

Next check performance of the caching with
Code:
nscd -g

You want to see:
Code:
CACHE: hosts

         CONFIG:
         enabled: yes
         per user cache: no
         avoid name service: no
         check file: yes
         check file interval: 0
         positive ttl: 3600
         negative ttl: 5
         keep hot count: 20
         hint size: 2048
         max entries: 0 (unlimited)

         STATISTICS:
         positive hits: 39
         negative hits: 2
         positive misses: 2
         negative misses: 3
         total entries: 2
         queries queued: 0
         queries dropped: 0
         cache invalidations: 0
         cache hit rate:       89.1


CACHE: ipnodes

         CONFIG:
         enabled: yes
         per user cache: no
         avoid name service: no
         check file: yes
         check file interval: 0
         positive ttl: 3600
         negative ttl: 5
         keep hot count: 20
         hint size: 2048
         max entries: 0 (unlimited)

         STATISTICS:
         positive hits: 1104
         negative hits: 2
         positive misses: 25
         negative misses: 3
         total entries: 4
         queries queued: 0
         queries dropped: 0
         cache invalidations: 18
         cache hit rate:       97.5

You may need to increase your local dns cache size. Primarily what you need is a sysadmin/network admin who knows this stuff, and is not following a rote playbook for how to maintain a network.

The optimal solution for dns problems like this is most often to set up caching DNS servers, and turn off nscd.

As a side note, it is very slightly possible your cache is becoming stale, possibly a DNS server has problems. If the cache stuff is working you may want to bounce the nscd process. This will clear the caches. So if an immediate rerun of your problem continues, then you have other issues, which IMO tend to be nasty.

N.B.:
This kind of advice is hard to give without actually being there, too many moving parts to do a decent job vicariously like this.
 

9 More Discussions You Might Find Interesting

1. UNIX for Dummies Questions & Answers

shell interpretation

I executed the following command in the korn shell: $ variable1="qwerty" ls | sort and the shell executed the 'ls | sort' command. I would have expected an error message from the shell, but instead of that the shell ran the 'ls | sort' command and didn't realize the variable assignement. ... (1 Reply)
Discussion started by: PhilippeCrokaer
1 Replies

2. UNIX for Dummies Questions & Answers

Interpretation of the uptime command

Hi there, do someone have detailed information how to interpret the uptime command or rather which values can be called normal? (i know what the information means, but i have no idea if these values are ok or to high: 3:02pm an 13:53, 2 Benutzer, Durchschnittslast: 10,06, 12,05, 13,00) ... (5 Replies)
Discussion started by: odin1999
5 Replies

3. UNIX for Advanced & Expert Users

SAR -b interpretation

I have used SAR -b to get some Unix cache / buffer metrics and the results are confusing me a bit. The pread/s & pwrit/s are showing 0. However the lread/s and lwrit/s are showing figures. I note also that the bread/s and bwrit/s are showing figures. I believe that pread/s and pwrit/s is not... (3 Replies)
Discussion started by: jimthompson
3 Replies

4. AIX

interpretation of sar

hello with a sar i have this result: System configuration: lcpu=48 ent=4.00 14:06:37 %usr %sys %wio %idle physc %entc 14:06:39 26 9 3 62 1.63 40.7 14:06:41 26 9 3 63 1.58 39.4 14:06:43 ... (0 Replies)
Discussion started by: pascalbout
0 Replies

5. Shell Programming and Scripting

Animation Ping on Solaris Like Cisco Ping

Hi, I develop simple animation ping script on Solaris Platform. It is like Cisco ping. Examples and source code are below. bash-3.00$ gokcell 152.155.180.8 30 Sending 30 Ping Packets to 152.155.180.8 !!!!!!!!!!!!!.!!!!!!!!!!!!!!!. % 93.33 success... % 6.66 packet loss...... (1 Reply)
Discussion started by: gokcell
1 Replies

6. Shell Programming and Scripting

Negating shell interpretation

I'm writing a Korn script but am having trouble because the shell interprets the asterisk in this case. Can anyone tell me if there is a way to fix this so that grep takes in STDIN without the interpretation? line="30 09 * * 1-4 /home/user01/bin/start" echo "$line" | grep 'start' (16 Replies)
Discussion started by: sprucio
16 Replies

7. Shell Programming and Scripting

How to get reason for ping failure using perls Net::Ping->new("icmp");?

Hi I am using perl to ping a list of nodes - with script below : $p = Net::Ping->new("icmp"); if ($p->ping($host,1)){ print "$host is alive.\n"; } else { print "$host is unreacheable.\n"; } $p->close();... (4 Replies)
Discussion started by: tavanagh
4 Replies

8. UNIX for Beginners Questions & Answers

Interpretation of UNIX command

what does the below do. echo * | xargs ls | wc –l echo * - Output a string comprising the name of each file in the working directory, with each name separated by a space. xargs ls - construct argument list command wc -l - it will pipe the output to the wc command, which will... (4 Replies)
Discussion started by: houmingc
4 Replies

9. Programming

Ping test sends mail when ping fails

help with bash script! im am working on this script to make sure my server will stay online, so i made this script.. HOSTS="192.168.138.155" COUNT=4 pingtest(){ for myhost in "$@" do ping -c "$COUNT" "$myhost" &&return 1 done return 0 } if pingtest $HOSTS #100% failed... (4 Replies)
Discussion started by: mort3924
4 Replies

LEARN ABOUT CENTOS

nscd.conf

NSCD.CONF(5)						     Linux Programmer's Manual						      NSCD.CONF(5)

NAME

       /etc/nscd.conf - name service cache daemon configuration file

DESCRIPTION

       The  file  /etc/nscd.conf  is read from nscd(8) at startup.  Each line specifies either an attribute and a value, or an attribute, service,
       and a value.  Fields are separated either by SPACE or TAB characters.  A '#' (number sign) indicates the beginning of a comment;  following
       characters, up to the end of the line, are not interpreted by nscd.

       Valid services are passwd, group, hosts, services or netgroup.

       logfile debug-file-name
	      Specifies name of the file to which debug info should be written.

       debug-level value
	      Sets the desired debug level.  The default is 0.

       threads number
	      This is the number of threads that are started to wait for requests.  At least five threads will always be created.

       max-threads number
	      Specifies the maximum number of threads.	The default is 32.

       server-user user
	      If  this option is set, nscd will run as this user and not as root.  If a separate cache for every user is used (-S parameter), this
	      option is ignored.

       stat-user user
	      Specifies the user who is allowed to request statistics.

       reload-count unlimited | number
	      Limit on the number of times a cached entry gets reloaded without being used before it gets removed.  The default is 5.

       paranoia <yes|no>
	      Enabling paranoia mode causes nscd to restart itself periodically.  The default is no.

       restart-interval time
	      Sets the restart interval to time seconds if periodic restart is enabled by enabling paranoia mode.  The default is 3600.

       enable-cache service <yes|no>
	      Enables or disables the specified service cache.	The default is no.

       positive-time-to-live service value
	      Sets the TTL (time-to-live) for positive entries (successful queries) in the specified cache for	service.   Value  is  in  seconds.
	      Larger values increase cache hit rates and reduce mean response times, but increase problems with cache coherence.

       negative-time-to-live service value
	      Sets  the  TTL  (time-to-live) for negative entries (unsuccessful queries) in the specified cache for service.  Value is in seconds.
	      Can result in significant performance improvements if there are several files owned by UIDs (user IDs) not in system databases  (for
	      example untarring the Linux kernel sources as root); should be kept small to reduce cache coherency problems.

       suggested-size service value
	      This is the internal hash table size, value should remain a prime number for optimum efficiency.	The default is 211.

       check-files service <yes|no>
	      Enables  or  disables  checking  the  file  belonging  to the specified service for changes.  The files are /etc/passwd, /etc/group,
	      /etc/hosts, /etc/services and /etc/netgroup.  The default is yes.

       persistent service <yes|no>
	      Keep the content of the cache for service over server restarts; useful when paranoia mode is set.  The default is no.

       shared service <yes|no>
	      The memory mapping of the nscd databases for service is shared with the clients so that they can directly search in them instead	of
	      having to ask the daemon over the socket each time a lookup is performed.  The default is no.

       max-db-size service bytes
	      The maximum allowable size, in bytes, of the database files for the service.  The default is 33554432.

       auto-propagate service <yes|no>
	      When  set to no for passwd or group service, then the .byname requests are not added to passwd.byuid or group.bygid cache.  This can
	      help with tables containing multiple records for the same ID.  The default is yes.  This option is valid only  for  services  passwd
	      and group.

NOTES

       The  default values stated in this manual page originate from the source code of nscd(8) and are used if not overriden in the configuration
       file.  The default values used in the configuration file of your distribution might differ.

SEE ALSO

       nscd(8)

COLOPHON

       This page is part of release 3.53 of the Linux man-pages project.  A description of the project, and information about reporting bugs,  can
       be found at http://www.kernel.org/doc/man-pages/.

GNU
								    2013-02-12							      NSCD.CONF(5)
All times are GMT -4. The time now is 08:09 AM.
Unix & Linux Forums Content Copyright 1993-2022. All Rights Reserved.
Privacy Policy