default netmask should be /16

Change-Id: I71b595c6ca912ed39a5438f8aa1c07314ccd45e5
diff --git a/config/onlab_develop_pod.yml b/config/onlab_develop_pod.yml
index a4be185..5039245 100644
--- a/config/onlab_develop_pod.yml
+++ b/config/onlab_develop_pod.yml
@@ -23,7 +23,7 @@
   #                 NAT-ed through this interface
   fabric_ip: '10.6.1.1/24'
   management_ip: '10.6.0.1/24'
-  external_ip: '10.90.0.251/24'
+  external_ip: '10.90.0.251/16'
   external_iface: 'eth0'
   skipTags: