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DNSSEC and Unix clients

Posted on 2014-09-04
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A company  has requested that DNSSEC be implemented in the environment.  The environment is a Windows 2008 R2 Active Directory with the DC's running DNS.  Setting up DNSSEC in DNS is relatively straightforward.  Most likely the company will also want to use IPSec with DNSSEC.   However, most of the client computers are Linux servers, so group policies are of no value here.

Would the Linux client be able to use DNSSEC?  If this is supported what are the commands on the Linux side to enable DNSSEC with IPSec?  How is this verified on the client?

I don't know if this matters but there are A records in DNS for all the Linux servers.
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Question by:BigmacMc
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by:gheist
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BIND v9 implemented DNSSEC in year 2000, and support is still there.

It has nothing to do if you use IPSEC or SSL or DSL or WPA2 or none, those are just communication channels

DNSSEC validation should be enabled in DNS servers(read first line), clients are deaf and blind unless you use special DNS parsing libraries.
Part of named.conf (taken from CentOS 6)
        dnssec-enable yes;
        dnssec-validation yes;
        dnssec-lookaside auto;
        /* Path to ISC DLV key */
        bindkeys-file "/etc/named.iscdlv.key";
        managed-keys-directory "/var/named/dynamic";
that enables DNSSEC validation on BIND name server by default.
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Jan Springer earned 500 total points
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If the linux box is a DNS client, then it doesn't need BIND (a DNS server).

It needs its servers specified in /etc/resolv.conf to return DNSSEC answers and it needs to not block those answers from TCP port 53.
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by:gheist
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Most network impact is not "port" number, but various firealls blocking large DNS packets (4K) used by DNSSEC
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by:Jan Springer
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And that's why I explicitly stated that traffic from TCP 53 needed to be allowed back in.

It's not just a DNSSEC thing.
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by:gheist
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e.g cisco inspect will drop 4K response packet that adds 5s wait to retry with 512 byte EDNS0 request
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by:Jan Springer
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i haven't configured a cisco firewall with 512 in  years.  that may be the default configuration but i've always changed it to 4096.
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by:BigmacMc
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Thanks everyone for your responses.

It is my understanding all the Linux servers are DNS clients pointing to Microsoft DNS servers, there are no Bind servers.  So my take away is etc/resolv.conf must be configured on the linux client servers to allow DNSSEC over port tcp 53.
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by:BigmacMc
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Is it safe to say that DNSSEC introduces sizable increase in DNS traffic?  That slow WAN/LAN links could possibly be impacted?
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by:Jan Springer
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If your /etc/resolv.conf points to a server that cannot handle DNSSEC, then you need to consider installing a server that does or upgrade the server configuration to do so.

Regardless of the size of the traffic, if you do allow for it, then you may be blocking traffic to some zones.
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by:gheist
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The traffic should have been accomodated 10 years ago.
Either way DNS does not use significant traffic.
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by:BigmacMc
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Thanks for the assistance
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