_cidr.sh

function bin2dec()
{
  echo -n $((2#${1}))
}

function dec2bin()
{
  D2B=({0..1}{0..1}{0..1}{0..1}{0..1}{0..1}{0..1}{0..1})
  echo -n ${D2B[${1}]}
}

function ip2bin()
{
  local X=${1}
  local OLDIFS="${IFS}"
  IFS="."
  set -- $X
  echo -n "$(dec2bin $1)$(dec2bin $2)$(dec2bin $3)$(dec2bin $4)"
  IFS="$OLDIFS"
}

function dec2ip() {
  printf "%d.%d.%d.%d\n" \
    $(( ($1 >> 24) & 255 )) \
    $(( ($1 >> 16) & 255 )) \
    $(( ($1 >> 8 ) & 255 )) \
    $(( ($1)       & 255 ))
}

function cidrSubnetMask()
{
  local ONES="11111111111111111111111111111111"
  local ZEROES="00000000000000000000000000000000"
  local BITS=$((32-${1}))
  echo ${ONES:0:$((${#ONES}-${BITS}))}${ZEROES:0:${BITS}}
}

function cidrNetworkAddress()
{
  local CIDR=${1}
  local CIDR_IPADDRESS=${CIDR%%/*}
  local CIDR_MASKBITS=${CIDR##*/}
  local BIN_IPADDRESS="$(ip2bin ${CIDR_IPADDRESS})"
  local BIN_SUBNETMASK="$(cidrSubnetMask ${CIDR_MASKBITS})"
  local R=""
  for I in {0..31}
  do
    R="${R}$(( 2#${BIN_IPADDRESS:$I:1} & 2#${BIN_SUBNETMASK:$I:1} ))"
  done
  echo -n "$(bin2dec ${R:0:8}).$(bin2dec ${R:8:8}).$(bin2dec ${R:16:8}).$(bin2dec ${R:24:8})"
}

function cidrSubnetMaxAddresses()
{
  echo -n $(( 1 << ( 32 - ${1/*\//} )))
}

function cidrSubnetMaxHosts()
{
  echo -n $(( $(cidrSubnetMaxAddresses ${1})-2 ))
}

function cidrBroadcastAddress()
{
  local CIDR=${1}
  local CIDR_IPADDRESS=${CIDR%%/*}
  local CIDR_MASKBITS=${CIDR##*/}
  local CIDR_NETWORK_ADDRESS=$(cidrNetworkAddress ${CIDR})
  local CIDR_NETWORK_ADDRESS_BIN=$(ip2bin ${CIDR_NETWORK_ADDRESS})
  local CIDR_NETWORK_ADDRESS_DEC=$(bin2dec ${CIDR_NETWORK_ADDRESS_BIN})
  local CIDR_MAX_ADDRESSES=$(cidrSubnetMaxAddresses ${CIDR})
  local CIDR_BROADCAST_ADDRESS_DEC=$(( ${CIDR_NETWORK_ADDRESS_DEC} + ${CIDR_MAX_ADDRESSES} - 1 ))
  echo -n $(dec2ip ${CIDR_BROADCAST_ADDRESS_DEC})
}

function cidrListIPAddresses() 
{
  local OLDIFS="$IFS"
  local CIDR="${1}"
  local CIDR_NETWORK_ADDRESS=$(cidrNetworkAddress ${CIDR})
  local CIDR_NETWORK_MASKBTIS=${CIDR##*/}
  local CIDR_NETWORK_MAXHOSTS=$(cidrSubnetMaxHosts ${CIDR})
  IFS="."
  set -- ${CIDR_NETWORK_ADDRESS}
  local IPS=$((0x$(printf "%02x%02x%02x%02x" $1 $2 $3 $4)))
  local VAL=""
  IFS="$OLDIFS"
  for ((N=0; N<CIDR_NETWORK_MAXHOSTS; N++))
    {
      VAL=$((IPS|N))
      printf "%d.%d.%d.%d\n"                  \
              $(( (VAL >> 24) & 255 ))        \
              $(( (VAL >> 16) & 255 ))        \
              $(( (VAL >> 8 ) & 255 ))        \
              $(( (VAL)       & 255 ))
    }
}

Bash SubNet Calculator Code Library