In another blog post I wrote that I’m using make to restart BIND and showed the following example:

root@dns:/etc/bind# cat Makefile
all:
        /usr/sbin/named-checkconf -z
        /usr/sbin/rndc reload

The all in the above Makefile is the default target used when calling make without options. The second line (Note that there is a TAB) runs a bind tool called named-checkconf with the option -z to check the BIND configuration and zones. If that works the third line is executed and BIND is restarted. If named-checkconf fails because you have a bad configuration the third line will not be executed.

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Some time ago I was asked why IPv6 wasn’t working. The customer had just configured some ipv6tables rules and IPv6 stopped working. See if you can spot the error in the following example rule set:

ip6tables -A INPUT -p ICMP -j ACCEPT
ip6tables -A INPUT -m conntrack --ctstate ESTABLISHED,RELATED -j ACCEPT
ip6tables -A INPUT -p tcp --dport ssh  -j ACCEPT
ip6tables -A INPUT -j DROP

The mistake is in line one. In IPv6 neighbor discovery and other functions rely on ICMPv6 which is a different protocol then ICMP. Some how ip6tables is fine with loading the ICMP protocol.

• CLAT in Linux Networkmanager
• DNS delegation
• jc - Convert command output to json
• Stratoshark - Analyse syscalls
• curl from start to end
• Security Bingo
• Linux Routing Fundamentals
• Packet where are you
• nftable-tracer