diff --git a/cluster/aws/util.sh b/cluster/aws/util.sh
index 5c68354d179..627b798d452 100755
--- a/cluster/aws/util.sh
+++ b/cluster/aws/util.sh
@@ -16,6 +16,19 @@
 
 # A library of helper functions and constant for the local config.
 
+# Experimental flags can be removed/renamed at any time.
+# The intent is to allow experimentation/advanced functionality before we
+# are ready to commit to supporting it.
+# Experimental functionality:
+#   KUBE_SHARE_MASTER=true
+#     Detect and reuse an existing master; useful if you want to
+#     create more nodes, perhaps with a different instance type or in
+#     a different subnet/AZ
+#   KUBE_SUBNET_CIDR=172.20.1.0/24
+#     Override the default subnet CIDR; useful if you want to create
+#     a second subnet.  The default subnet is 172.20.0.0/24.  The VPC
+#     is created with 172.20.0.0/16; you must pick a sub-CIDR of that.
+
 # Use the config file specified in $KUBE_CONFIG_FILE, or default to
 # config-default.sh.
 KUBE_ROOT=$(dirname "${BASH_SOURCE}")/../..
@@ -25,7 +38,9 @@ source "${KUBE_ROOT}/cluster/common.sh"
 ALLOCATE_NODE_CIDRS=true
 
 NODE_INSTANCE_PREFIX="${INSTANCE_PREFIX}-minion"
-ASG_NAME="${NODE_INSTANCE_PREFIX}-group"
+
+# The Auto Scaling Group (ASG) name must be unique, so we include the zone
+ASG_NAME="${NODE_INSTANCE_PREFIX}-group-${ZONE}"
 
 # We could allow the master disk volume id to be specified in future
 MASTER_DISK_ID=
@@ -53,9 +68,15 @@ AWS_CMD="aws --output json ec2"
 AWS_ELB_CMD="aws --output json elb"
 AWS_ASG_CMD="aws --output json autoscaling"
 
-INTERNAL_IP_BASE=172.20.0
+VPC_CIDR_BASE=172.20
 MASTER_IP_SUFFIX=.9
-MASTER_INTERNAL_IP=${INTERNAL_IP_BASE}${MASTER_IP_SUFFIX}
+MASTER_INTERNAL_IP=${VPC_CIDR_BASE}.0${MASTER_IP_SUFFIX}
+VPC_CIDR=${VPC_CIDR_BASE}.0.0/16
+SUBNET_CIDR=${VPC_CIDR_BASE}.0.0/24
+if [[ -n "${KUBE_SUBNET_CIDR:-}" ]]; then
+  echo "Using subnet CIDR override: ${KUBE_SUBNET_CIDR}"
+  SUBNET_CIDR=${KUBE_SUBNET_CIDR}
+fi
 
 MASTER_SG_NAME="kubernetes-master-${CLUSTER_ID}"
 MINION_SG_NAME="kubernetes-minion-${CLUSTER_ID}"
@@ -82,15 +103,20 @@ function get_vpc_id {
 }
 
 function get_subnet_id {
-  python -c "import json,sys; lst = [str(subnet['SubnetId']) for subnet in json.load(sys.stdin)['Subnets'] if subnet['VpcId'] == '$1' and subnet['AvailabilityZone'] == '$2']; print ''.join(lst)"
+  local vpc_id=$1
+  local az=$2
+  $AWS_CMD --output text describe-subnets \
+           --filters Name=tag:KubernetesCluster,Values=${CLUSTER_ID} \
+                     Name=availabilityZone,Values=${az} \
+                     Name=vpc-id,Values=${vpc_id} \
+           --query Subnets[].SubnetId
 }
 
 function get_igw_id {
-  python -c "import json,sys; lst = [str(igw['InternetGatewayId']) for igw in json.load(sys.stdin)['InternetGateways'] for attachment in igw['Attachments'] if attachment['VpcId'] == '$1']; print ''.join(lst)"
-}
-
-function get_route_table_id {
-  python -c "import json,sys; lst = [str(route_table['RouteTableId']) for route_table in json.load(sys.stdin)['RouteTables'] if route_table['VpcId'] == '$1']; print ''.join(lst)"
+  local vpc_id=$1
+  $AWS_CMD --output text describe-internet-gateways \
+           --filters Name=attachment.vpc-id,Values=${vpc_id} \
+           --query InternetGateways[].InternetGatewayId
 }
 
 function get_elbs_in_vpc {
@@ -163,6 +189,7 @@ function query-running-minions () {
            --filters Name=instance-state-name,Values=running \
                      Name=vpc-id,Values=${VPC_ID} \
                      Name=tag:KubernetesCluster,Values=${CLUSTER_ID} \
+                     Name=tag:aws:autoscaling:groupName,Values=${ASG_NAME} \
                      Name=tag:Role,Values=${MINION_TAG} \
            --query ${query}
 }
@@ -701,7 +728,7 @@ function kube-up {
   fi
   if [[ -z "$VPC_ID" ]]; then
 	  echo "Creating vpc."
-	  VPC_ID=$($AWS_CMD create-vpc --cidr-block $INTERNAL_IP_BASE.0/16 | json_val '["Vpc"]["VpcId"]')
+	  VPC_ID=$($AWS_CMD create-vpc --cidr-block ${VPC_CIDR} | json_val '["Vpc"]["VpcId"]')
 	  $AWS_CMD modify-vpc-attribute --vpc-id $VPC_ID --enable-dns-support '{"Value": true}' > $LOG
 	  $AWS_CMD modify-vpc-attribute --vpc-id $VPC_ID --enable-dns-hostnames '{"Value": true}' > $LOG
 	  add-tag $VPC_ID Name kubernetes-vpc
@@ -713,23 +740,26 @@ function kube-up {
   create-dhcp-option-set
 
   if [[ -z "${SUBNET_ID:-}" ]]; then
-    SUBNET_ID=$($AWS_CMD describe-subnets --filters Name=tag:KubernetesCluster,Values=${CLUSTER_ID} | get_subnet_id $VPC_ID $ZONE)
+    SUBNET_ID=$(get_subnet_id $VPC_ID $ZONE)
   fi
 
   if [[ -z "$SUBNET_ID" ]]; then
     echo "Creating subnet."
-    SUBNET_ID=$($AWS_CMD create-subnet --cidr-block $INTERNAL_IP_BASE.0/24 --vpc-id $VPC_ID --availability-zone ${ZONE} | json_val '["Subnet"]["SubnetId"]')
+    SUBNET_ID=$($AWS_CMD create-subnet --cidr-block ${SUBNET_CIDR} --vpc-id $VPC_ID --availability-zone ${ZONE} | json_val '["Subnet"]["SubnetId"]')
     add-tag $SUBNET_ID KubernetesCluster ${CLUSTER_ID}
   else
     EXISTING_CIDR=$($AWS_CMD describe-subnets --subnet-ids ${SUBNET_ID} --query Subnets[].CidrBlock --output text)
-    echo "Using existing CIDR $EXISTING_CIDR"
-    INTERNAL_IP_BASE=${EXISTING_CIDR%.*}
-    MASTER_INTERNAL_IP=${INTERNAL_IP_BASE}${MASTER_IP_SUFFIX}
+    echo "Using existing subnet with CIDR $EXISTING_CIDR"
+    VPC_CIDR=$($AWS_CMD describe-vpcs --vpc-ids ${VPC_ID} --query Vpcs[].CidrBlock --output text)
+    echo "VPC CIDR is $VPC_CIDR"
+    VPC_CIDR_BASE=${VPC_CIDR%.*.*}
+    MASTER_INTERNAL_IP=${VPC_CIDR_BASE}.0${MASTER_IP_SUFFIX}
+    echo "Assuming MASTER_INTERNAL_IP=${MASTER_INTERNAL_IP}"
   fi
 
   echo "Using subnet $SUBNET_ID"
 
-  IGW_ID=$($AWS_CMD describe-internet-gateways | get_igw_id $VPC_ID)
+  IGW_ID=$(get_igw_id $VPC_ID)
   if [[ -z "$IGW_ID" ]]; then
 	  echo "Creating Internet Gateway."
 	  IGW_ID=$($AWS_CMD create-internet-gateway | json_val '["InternetGateway"]["InternetGatewayId"]')
@@ -791,6 +821,33 @@ function kube-up {
   # HTTPS to the master is allowed (for API access)
   authorize-security-group-ingress "${MASTER_SG_ID}" "--protocol tcp --port 443 --cidr 0.0.0.0/0"
 
+  # KUBE_SHARE_MASTER is used to add minions to an existing master
+  if [[ "${KUBE_SHARE_MASTER:-}" == "true" ]]; then
+    # Detect existing master
+    detect-master
+
+    # Start minions
+    start-minions
+  else
+    # Create the master
+    start-master
+
+    # Start minions
+    start-minions
+
+    # Wait for the master to be ready
+    wait-master
+
+    # Build ~/.kube/config
+    build-config
+  fi
+
+  # Check the cluster is OK
+  check-cluster
+}
+
+# Starts the master node
+function start-master() {
   # Get or create master persistent volume
   ensure-master-pd
 
@@ -952,7 +1009,10 @@ function kube-up {
     attempt=$(($attempt+1))
     sleep 10
   done
+}
 
+# Creates an ASG for the minion nodes
+function start-minions() {
   echo "Creating minion configuration"
   generate-minion-user-data > "${KUBE_TEMP}/minion-user-data"
   local public_ip_option
@@ -1007,9 +1067,11 @@ function kube-up {
     attempt=$(($attempt+1))
     sleep 10
   done
+}
 
+# Wait for the master to be started
+function wait-master() {
   detect-master > $LOG
-  detect-minions > $LOG
 
   # TODO(justinsb): This is really not necessary any more
   # Wait 3 minutes for cluster to come up.  We hit it with a "highstate" after that to
@@ -1038,7 +1100,11 @@ function kube-up {
   done
 
   echo "Kubernetes cluster created."
+}
 
+# Creates the ~/.kube/config file, getting the information from the master
+# The master much be running and set in KUBE_MASTER_IP
+function build-config() {
   # TODO use token instead of kube_auth
   export KUBE_CERT="/tmp/$RANDOM-kubecfg.crt"
   export KUBE_KEY="/tmp/$RANDOM-kubecfg.key"
@@ -1057,11 +1123,16 @@ function kube-up {
 
     create-kubeconfig
   )
+}
 
+# Sanity check the cluster and print confirmation messages
+function check-cluster() {
   echo "Sanity checking cluster..."
 
   sleep 5
 
+  detect-minions > $LOG
+
   # Don't bail on errors, we want to be able to print some info.
   set +e
 
@@ -1127,20 +1198,26 @@ function kube-down {
       done
     fi
 
-    if [[ -n $(${AWS_ASG_CMD} --output text describe-auto-scaling-groups --auto-scaling-group-names ${ASG_NAME} --query AutoScalingGroups[].AutoScalingGroupName) ]]; then
-      echo "Deleting auto-scaling group: ${ASG_NAME}"
-      ${AWS_ASG_CMD} delete-auto-scaling-group --force-delete --auto-scaling-group-name ${ASG_NAME}
-    fi
-    if [[ -n $(${AWS_ASG_CMD} --output text describe-launch-configurations --launch-configuration-names ${ASG_NAME} --query LaunchConfigurations[].LaunchConfigurationName) ]]; then
-      echo "Deleting auto-scaling launch configuration: ${ASG_NAME}"
-      ${AWS_ASG_CMD} delete-launch-configuration --launch-configuration-name ${ASG_NAME}
-    fi
-
     echo "Deleting instances in VPC: ${vpc_id}"
     instance_ids=$($AWS_CMD --output text describe-instances \
                             --filters Name=vpc-id,Values=${vpc_id} \
                                       Name=tag:KubernetesCluster,Values=${CLUSTER_ID} \
                             --query Reservations[].Instances[].InstanceId)
+
+    asg_groups=$($AWS_CMD   --output text describe-instances \
+                            --query 'Reservations[].Instances[].Tags[?Key==`aws:autoscaling:groupName`].Value[]' \
+                            --instance-ids ${instance_ids})
+    for asg_group in ${asg_groups}; do
+      if [[ -n $(${AWS_ASG_CMD} --output text describe-auto-scaling-groups --auto-scaling-group-names ${asg_group} --query AutoScalingGroups[].AutoScalingGroupName) ]]; then
+        echo "Deleting auto-scaling group: ${asg_group}"
+        ${AWS_ASG_CMD} delete-auto-scaling-group --force-delete --auto-scaling-group-name ${asg_group}
+      fi
+      if [[ -n $(${AWS_ASG_CMD} --output text describe-launch-configurations --launch-configuration-names ${asg_group} --query LaunchConfigurations[].LaunchConfigurationName) ]]; then
+        echo "Deleting auto-scaling launch configuration: ${asg_group}"
+        ${AWS_ASG_CMD} delete-launch-configuration --launch-configuration-name ${asg_group}
+      fi
+    done
+
     if [[ -n "${instance_ids}" ]]; then
       $AWS_CMD terminate-instances --instance-ids ${instance_ids} > $LOG
       echo "Waiting for instances to be deleted"