notes about external connectivity
diff --git a/xos/configurations/cord/README-VTN.md b/xos/configurations/cord/README-VTN.md
index 7b0e0d8..5000b23 100644
--- a/xos/configurations/cord/README-VTN.md
+++ b/xos/configurations/cord/README-VTN.md
@@ -113,3 +113,26 @@
11. You should see the pings arrive and responses sent out. Note that the ping responses will not reach Slice-1, since VTN traffic is unidirectional.
12. Delete the Tenancy relation you created in Step #7. The ping traffic should no longer appear in the tcpdump.
+Getting external connectivity working on cloudlab
+
+Inside of vSG:
+ ip link add link eth0 eth0.500 type vlan id 500
+ ifconfig eth0.500 up
+ route del default gw 172.27.0.1
+ /sbin/ifconfig eth0.500 10.123.0.3
+ route del -net 10.0.0.0 netmask 255.0.0.0 dev eth0.500 # only need to do this if this route exists
+ route add -net 10.123.0.0 netmask 255.255.255.0 dev eth0.500
+ route add default gw 10.123.0.1
+ arp -s 10.123.0.1 00:8c:fa:5b:09:d8
+
+On head node:
+ ifconfig eth2 10.123.0.1
+ iptables --table nat --append POSTROUTING --out-interface br-ex -j MASQUERADE
+ arp -s 10.123.0.3 fa:16:3e:ea:11:0a
+
+Substitute for your installation:
+ 10.123.0.3 = wan_ip of vSG
+ 10.123.0.1 = wan gateway
+ fa:16:3e:ea:11:0a = wan_mac of vSG
+ 00:8c:fa:5b:09:d8 = wan_mac of gateway
+