Archive for 'DNS & BIND'

Creating Bind query log statistics with dnsrecon

A month or two back I was investigating a production issue and wanted to visualize our Bind query logs. The Bind statistics channel looked useful but there wasn’t enough data to help me troubleshoot my issue. In the spirit of software re-use I looked at a few opensource query log parsing utilities. The programs I […]

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 @216.92.61.30 prefetch.net 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 […]

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