Bash script to send quers tr

dns.sh

#
# To execute
# ./dns.sh google.com
#
# 69.69.69.69, 70.70.70.70, 71.71.71.71 are example IPs for ISP DNS servers
#
# Common CDNs to test for:
#
# se2.itunes.apple.com -> Akamai CDN
# i.scdn.co -> Fastly CDN
# alexa.amazon.co.in -> Cloudfront CDN
# labtest-gartner.lldns.net -> Limelight CDN

#!/bin/bash

dns_servers=(oc-bom1 69.69.69.69 70.70.70.70 71.71.71.71 8.8.8.8 1.1.1.1)

for i in "${dns_servers[@]}"; do
  echo "+ ---- $i ---- +"

  # ISP's DNS servers here...
  if [[ $i == "69.69.69.69" ]] || [[ $i == "70.70.70.70" ]] || [[ $i == "71.71.71.71" ]]; then
    a=$(kdig +short @$i "$1")

  # Using alternate port for Quad9
  elif [[ $i == "9.9.9.11" ]]; then
     a=$(kdig +short -p 9953 @$i "$1")

  # for cloud VMs, specify port after query, e.g. ./dns.sh google.com 4300
  elif [[ $i == "oc-bom1" ]] || [[ $i == "oracle1" ]]; then

    if [[ ! "$2" ]]; then
      printf "No port specified. Defaulting to port 1100\n\n"
      a=$(dig +short @$i -p 1100 "$1" )
    else
      a=$(dig +stats +short @$i -p $2 "$1" )
    fi

  # Send query without ECS, usage: ./dns.sh google.com no-ecs
  elif [[ $2 == "no-ecs" ]]; then
    echo "Using 0.0.0.0/0 as ECS data"
    a=$(kdig +short +tls +subnet=0.0.0.0/0 @$i "$1")

  # Send queries over DNS-over-TLS; to mitigate ISP DNS redirection
  # If your ISP does not do this, you can remove the +tls flag
  else
    a=$(kdig +short +tls @$i "$1")
  fi
  echo "$a"
  ping -c 1 -W 1 $(echo "$a" | tail -n1) | grep icmp
  echo ""
done