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82 lines
2.0 KiB
Bash
82 lines
2.0 KiB
Bash
#!/usr/bin/env bash
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# vim:ts=4:sts=4:sw=4:et
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#
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# Author: Hari Sekhon
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# Date: 2019-03-14 18:41:35 +0000 (Thu, 14 Mar 2019)
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#
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# https://github.com/HariSekhon/DevOps-Bash-tools
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#
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# License: see accompanying Hari Sekhon LICENSE file
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#
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# If you're using my code you're welcome to connect with me on LinkedIn and optionally send me feedback to help steer this or other code I publish
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#
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# https://www.linkedin.com/in/HariSekhon
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#
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set -euo pipefail
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[ -n "${DEBUG:-}" ] && set -x
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usage(){
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if [ -n "$*" ]; then
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echo "$@"
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echo
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fi
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cat <<EOF
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Scans locally attached networks and prints duplicate MAC addresses
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Useful for finding duplicate MACs and also finding hosts behind a VIP or similar floating address (VRRP, HSRP)
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Uses fping to ping all addresses on all local subnets and then checks the local arp cache
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Caveat: won't find a VIP on the local host this script is run on
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usage: ${0##*/}
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EOF
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exit 3
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}
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until [ $# -lt 1 ]; do
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case $1 in
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-h|--help) usage
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;;
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*) usage "unknown argument: $1"
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;;
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esac
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shift || :
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done
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if [ -z "${NOSCAN:-}" ]; then
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if [ "$(uname -s)" = "Darwin" ]; then
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networks="$(netstat -rn | awk '/link#/{print $1}' | grep -e '[[:digit:]]\+\.[[:digit:]]\+\.[[:digit:]]\+\.[[:digit:]]\+')"
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else # assume Linux
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networks="$(ip addr | awk '/inet /{print $2}' | grep -v '^127\.')"
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fi
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for network in $networks; do
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echo "scanning network $network..." >&2
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fping -q -r 0 -c 1 -B 1 -g "$network" >&2 || :
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done
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fi
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# Linux
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#arp -e |
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# BSD - more portable, both Linux and Mac support this
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arp -a |
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# incomplete seems to only appear on arp on Linux, for both -a and -e formats
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# Linux arp -e
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#awk '!/incomplete/{print $3}' |
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# BSD arp -a (works on Linux too)
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awk '!/incomplete/{print $4}' |
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grep -vi "ff:ff:ff:ff:ff:ff" |
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sort |
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uniq -d |
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while read -r mac; do
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# Linux
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#arp -e |
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# BSD - more portable, both Linux and Mac support this
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arp -a |
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grep "$mac"
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done
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