Description of problem:
Like the file "ifup-eth" the "ifup-ovs" does not update the ARP cache of neighbouring computers, as in the network cannot observe GARP requests sent from br-ex made upon OVS.

As reported in of my customer's ticket, During the 2nd openstack overcloud deployment(if the first overcloud deployment fails due to any reason) then it is required to send GARP before setting ip of the bridge.

As it does not send the GARP requests in the network, the firewall/gateway in the network keeps the older ARP entries with older mac address and ip.

If the same ip used from the previous failed deployment gets used again in next overcloud deployment then it cases failure to reach the node on which same ip has been assigned which was used in the previous failed overcloud deployment.

The workaround for this issue is to flush the ARP table on the firewall but I am looking if it is possible that ifup-ovs could make gratuitous arp while the IP gets assigned to it so that it will update the firewall for the new Macaddress on that IP.

The ifup-eth does update the arp while it assign the ip but in the ifup-ovs's case it does not.


~~~~~~~~~~~~
 
file -> initscripts-9.49.41/sysconfig/network-scripts/ifup-eth

 # set IP address(es)
        for idx in {0..256} ; do
            if [ -z "${ipaddr[$idx]}" ]; then
                break
            fi

            if ! LC_ALL=C ip addr ls ${REALDEVICE} | LC_ALL=C grep -q "${ipaddr[$idx]}/${prefix[$idx]}" ; then
                if [ "${REALDEVICE}" != "lo" ] && [ "${arpcheck[$idx]}" != "no" ] ; then
                    ARPING=$(/sbin/arping -c 2 -w ${ARPING_WAIT:-3} -D -I ${REALDEVICE} ${ipaddr[$idx]})
                    if [ $? = 1 ]; then
                        ARPINGMAC=$(echo $ARPING |  sed -ne 's/.*\[\(.*\)\].*/\1/p')
                        net_log $"Error, some other host ($ARPINGMAC) already uses address ${ipaddr[$idx]}."
                        exit 1
                    fi
                fi

                if ! ip addr add ${ipaddr[$idx]}/${prefix[$idx]} \
                    brd ${broadcast[$idx]:-+} dev ${REALDEVICE} ${SCOPE} label ${DEVICE}; then
                    net_log $"Error adding address ${ipaddr[$idx]} for ${DEVICE}."
                fi
            fi

            if [ -n "$SRCADDR" ]; then
                sysctl -w "net.ipv4.conf.${SYSCTLDEVICE}.arp_filter=1" >/dev/null 2>&1
            fi

# update ARP cache of neighboring computers
            if ! is_false "${arpupdate[$idx]}" && [ "${REALDEVICE}" != "lo" ]; then
                /sbin/arping -q -A -c 1 -I ${REALDEVICE} ${ipaddr[$idx]}
                ( sleep 2;
                /sbin/arping -q -U -c 1 -I ${REALDEVICE} ${ipaddr[$idx]} ) > /dev/null 2>&1 < /dev/null &
            fi

~~~~~~~~~~~~

But the same as above is not called in the ifup-ovs.

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