Archive for 'DNS & BIND'

The subtleties between the NXDOMAIN, NOERROR and NODATA DNS response codes

This past weekend I spent some time troubleshooting a DNS timeout issue. During my debugging session I noticed some subtle differences when querying an A and AAAA record with dig: $ dig +answer @ a ……. ;; Got answer: ;; ->>HEADERHEADERHEADER

Bind’s strict zone checking feature is part of CentOS 6

I recently moved a bind installation from CentOS 5 to CentOS 6. As part of the move I built out a new server with CentOS 6, staged the bind chroot packages and then proceeded to copy all of the zone files from the CentOS 5 server to the CentOS 6 server. Once all the pieces […]

Configuring NSCD to cache DNS host lookups

I haven’t really spent that much time configuring nscd, so I thought I would take a crack at it this morning while sipping my cup of joe. Looking at one of my production hosts, I queried for the “host” cache statistics. This is the nscd cache which keeps DNS lookups. With the nscd daemon running, […]

Using dnscap to debug DNS problems on Linux hosts

DNS can often make a SysAdmins life difficult, since a misconfigured entry or a broken authoritative DNS server will cause things to fail in odd ways. If you are fortunate enough to use Linux on your servers and desktops, you have a slew of utilities available to look at problems. I’ve discussed a few of […]

Configuring a caching only DNS server on Solaris hosts

While investigating a performance issue a few weeks back, I noticed that a couple of our Solaris hosts were sending 10s of thousands of DNS requests to our authoritative DNS servers. Since the application was broken and unable to cache DNS records, I decided to configure a local caching only DNS server to reduce load […]

Getting DNS ping (aka nsping) to compile on Linux hosts

While debugging a DNS issue this week, I wanted to run my trusty old friend nsping on my Linux desktop. I grabbed the source from the FreeBSD source site, checked to make sure the bits were legit, then proceeded to compile it: $ make cc -g -c -o nsping.o nsping.c In file included from nsping.c:13: […]

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