sonic-buildimage/files/scripts/arp_update

#!/bin/bash
#
# usage:
# arp_update: Send gratuitous ARP requests to VLAN member neighbors to refresh
# the neighbors state.

while /bin/true; do
  VLAN=`sonic-cfggen -d -v 'VLAN.keys() | join(" ") if VLAN'`
  for vlan in $VLAN; do
      # generate a list of arping commands:
      #   arping -q -w 0 -c 1 -i <VLAN interface> <IP 1>;
      #   arping -q -w 0 -c 1 -i <VLAN interface> <IP 2>;
      #   ...
      arpingcmd="sed -e 's/ / -i /' -e 's/^/arping -q -w 0 -c 1 /' -e 's/$/;/'"
      ipcmd="ip -4 neigh show | grep $vlan | cut -d ' ' -f 1,3 | $arpingcmd"

      eval `eval $ipcmd`
  done
  sleep 300
done