diff --git a/configs/stage3_ubuntu/opt/mlab/bin/write-metadata.sh b/configs/stage3_ubuntu/opt/mlab/bin/write-metadata.sh
index 4e0ef13..9e2ab7a 100755
--- a/configs/stage3_ubuntu/opt/mlab/bin/write-metadata.sh
+++ b/configs/stage3_ubuntu/opt/mlab/bin/write-metadata.sh
@@ -10,3 +10,22 @@ mkdir -p $METADATA_DIR
 
 # Write the kernel version
 uname -r | tr -d '\n' > $METADATA_DIR/kernel-version
+
+# Write out the metadata value for "managed". This will allow data users to know
+# what environment the test was run. For a "full" site M-Lab manages both the
+# machine and an upstream switch. For "minimal" deployments M-Lab only manages
+# the machine, and nothing upstream.
+PREFIX_LEN=$(egrep -o 'epoxy.ipv4=[^ ]+' /proc/cmdline | cut -d= -f2 | cut -d, -f1 | cut -d/ -f 2)
+case "$PREFIX_LEN" in
+  26)
+    MANAGED="switch,machine"
+    ;;
+  28|29)
+    MANAGED="machine"
+    ;;
+  *)
+    echo "ERROR: cannot set MANAGED. Unknown prefix length ${PREFIX_LEN}"
+    MANAGED="unknown"
+    ;;
+esac
+echo -n "$MANAGED" > $METADATA_DIR/managed
diff --git a/configs/virtual_ubuntu/opt/mlab/bin/write-metadata.sh b/configs/virtual_ubuntu/opt/mlab/bin/write-metadata.sh
index 8cef4ef..53b4829 100755
--- a/configs/virtual_ubuntu/opt/mlab/bin/write-metadata.sh
+++ b/configs/virtual_ubuntu/opt/mlab/bin/write-metadata.sh
@@ -63,3 +63,7 @@ echo -n ${machine_type##*/} > $METADATA_DIR/machine-type
 echo -n "PREMIUM" > $METADATA_DIR/network-tier
 
 echo -n $(uname -r) > $METADATA_DIR/kernel-version
+
+# For virtual machines this indicates that M-Lab manages only the machine and
+# none of the infrastructure upstream of it.
+echo -n "machine" > $METADATA_DIR/managed