How to split DNS DKIM records
DNS TXT records do have a limitation. Strings must not be longer than 255 Bytes. This limitation can hurt you with SPF records or DKIM records. In this case you…
Posts related to computer networks
Use netcat instead of telnet
Network engineers often use telnet to establish a connection to a service on a remote server. Apple dropped the telnet and ftp client in macOS High Sierra. First I was…
Hide your version of BIND
To hide your version of bind, enter the following value to your named.conf version "[NONE]"; in the option section: options { directory "/var/lib/bind"; version "[NONE]"; }; Check the value with…
Subnet Masks
A subnetwork, or subnet, is a logically visible, distinctly addressed part of a single Internet Protocol network. The process of subnetting is the division of a computer network into groups of computers that have a common,…
pcap filter
tcpdump and ngrep are both based on libpcap. Therefore both use the same filter expressions. Here is the manual page of the ⇒pcap filter expression. These filter expressions are also…
Network grep “ngrep” on macOS
Sometimes it is very practical to use grep, to find a specific regular expression in some files. It would also be very practical to have the grep functionality on the…