Comment 6 for bug 1557294

Possible workaround: This looks like, the issue is with 'unstack.sh' - which does not clean up the ovs / network setup when run. Therefore its not required to re-create your VM from the start again, instead just undo/del all the virtual networking setup {br-int, br-eth1, br-tun} before running `stack.sh` again.

for instance:
ovs-vsctl del-br br-int
ovs-vsctl del-br br-eth1

#ip add
ip add
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
       valid_lft forever preferred_lft forever
    inet6 ::1/128 scope host
       valid_lft forever preferred_lft forever
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP group default qlen 1000
    link/ether 08:00:27:b6:ee:51 brd ff:ff:ff:ff:ff:ff
    inet 10.0.2.15/24 brd 10.0.2.255 scope global eth0
       valid_lft forever preferred_lft forever
    inet6 fe80::a00:27ff:feb6:ee51/64 scope link
       valid_lft forever preferred_lft forever
3: eth1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP group default qlen 1000
    link/ether 08:00:27:92:b3:8f brd ff:ff:ff:ff:ff:ff
    inet 192.168.27.100/24 brd 192.168.27.255 scope global eth1
       valid_lft forever preferred_lft forever
    inet6 fe80::a00:27ff:fe92:b38f/64 scope link
       valid_lft forever preferred_lft forever
4: eth2: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN group default qlen 1000
    link/ether 08:00:27:5a:8b:41 brd ff:ff:ff:ff:ff:ff
5: virbr0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc noqueue state DOWN group default
    link/ether 86:7a:26:7a:1b:fd brd ff:ff:ff:ff:ff:ff
    inet 192.168.122.1/24 brd 192.168.122.255 scope global virbr0
       valid_lft forever preferred_lft forever
6: ovs-system: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN group default
    link/ether 1e:8c:3a:e8:06:7e brd ff:ff:ff:ff:ff:ff
7: br-int: <BROADCAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UNKNOWN group default
    link/ether 66:0c:99:93:c7:48 brd ff:ff:ff:ff:ff:ff
    inet6 fe80::e03e:97ff:fe76:f5c6/64 scope link
       valid_lft forever preferred_lft forever
8: br-ex: <BROADCAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UNKNOWN group default
    link/ether ea:9a:1d:8b:a0:4d brd ff:ff:ff:ff:ff:ff
    inet 172.24.4.1/24 scope global br-ex
       valid_lft forever preferred_lft forever
    inet6 2001:db8::2/64 scope global
       valid_lft forever preferred_lft forever
    inet6 fe80::3042:50ff:fe66:3172/64 scope link
       valid_lft forever preferred_lft forever
9: br-tun: <BROADCAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UNKNOWN group default
    link/ether a6:c2:33:3b:ff:46 brd ff:ff:ff:ff:ff:ff
    inet6 fe80::40d6:2ff:fed5:a68f/64 scope link
       valid_lft forever preferred_lft forever