Reverse DNS lookup

PTR record for an IP address

dig +short -x 8.8.8.8
tool
linux133 commands
tags
linuxnetworkdns

More linux commands

  • Trace DNS delegation
    dig +trace example.com

    Follow full DNS resolution chain from root nameservers

  • Show established TCP connections
    ss -tnp state established

    All established TCP connections with process info

  • Count connections per state
    ss -tan | awk 'NR>1{print $1}' | sort | uniq -c | sort -rn

    How many connections are in ESTABLISHED, TIME_WAIT, etc.

  • Traceroute with MTU discovery
    mtr --report --tcp --port 443 example.com

    Combine traceroute and ping; TCP mode to bypass ICMP blocks

  • Test MTU path
    ping -M do -s 1472 -c 3 8.8.8.8

    Send DF-bit ping of 1500-byte frames to detect MTU issues

all 133 linux commands