diff --git a/src/main/java/org/onosproject/segmentrouting/SegmentRoutingManager.java b/src/main/java/org/onosproject/segmentrouting/SegmentRoutingManager.java
index 6c25b7d..bd89102 100644
--- a/src/main/java/org/onosproject/segmentrouting/SegmentRoutingManager.java
+++ b/src/main/java/org/onosproject/segmentrouting/SegmentRoutingManager.java
@@ -33,6 +33,7 @@
 import org.onosproject.core.CoreService;
 import org.onosproject.event.Event;
 import org.onosproject.incubator.net.config.basics.McastConfig;
+import org.onosproject.incubator.net.intf.InterfaceService;
 import org.onosproject.mastership.MastershipService;
 import org.onosproject.net.Device;
 import org.onosproject.net.DeviceId;
@@ -113,8 +114,7 @@
 @Component(immediate = true)
 public class SegmentRoutingManager implements SegmentRoutingService {
 
-    private static Logger log = LoggerFactory
-            .getLogger(SegmentRoutingManager.class);
+    private static Logger log = LoggerFactory.getLogger(SegmentRoutingManager.class);
 
     @Reference(cardinality = ReferenceCardinality.MANDATORY_UNARY)
     protected CoreService coreService;
@@ -141,7 +141,7 @@
     protected StorageService storageService;
 
     @Reference(cardinality = ReferenceCardinality.MANDATORY_UNARY)
-    protected NetworkConfigRegistry cfgService;
+    public NetworkConfigRegistry cfgService;
 
     @Reference(cardinality = ReferenceCardinality.MANDATORY_UNARY)
     protected ComponentConfigService compCfgService;
@@ -155,11 +155,14 @@
     @Reference(cardinality = ReferenceCardinality.MANDATORY_UNARY)
     protected CordConfigService cordConfigService;
 
+    @Reference(cardinality = ReferenceCardinality.MANDATORY_UNARY)
+    public InterfaceService interfaceService;
+
     protected ArpHandler arpHandler = null;
     protected IcmpHandler icmpHandler = null;
     protected IpHandler ipHandler = null;
     protected RoutingRulePopulator routingRulePopulator = null;
-    protected ApplicationId appId;
+    public ApplicationId appId;
     protected DeviceConfiguration deviceConfiguration = null;
 
     protected DefaultRoutingHandler defaultRoutingHandler = null;
@@ -256,7 +259,7 @@
     /**
      * Segment Routing App ID.
      */
-    public static final String SR_APP_ID = "org.onosproject.segmentrouting";
+    public static final String APP_NAME = "org.onosproject.segmentrouting";
     /**
      * The starting value of per-subnet VLAN ID assignment.
      */
@@ -268,7 +271,7 @@
 
     @Activate
     protected void activate() {
-        appId = coreService.registerApplication(SR_APP_ID);
+        appId = coreService.registerApplication(APP_NAME);
 
         log.debug("Creating EC map nsnextobjectivestore");
         EventuallyConsistentMapBuilder<NeighborSetNextObjectiveStoreKey, Integer>
@@ -894,29 +897,28 @@
     }
 
     private class InternalConfigListener implements NetworkConfigListener {
-        SegmentRoutingManager segmentRoutingManager;
+        SegmentRoutingManager srManager;
 
         /**
          * Constructs the internal network config listener.
          *
-         * @param srMgr segment routing manager
+         * @param srManager segment routing manager
          */
-        public InternalConfigListener(SegmentRoutingManager srMgr) {
-            this.segmentRoutingManager = srMgr;
+        public InternalConfigListener(SegmentRoutingManager srManager) {
+            this.srManager = srManager;
         }
 
         /**
          * Reads network config and initializes related data structure accordingly.
          */
         public void configureNetwork() {
-            deviceConfiguration = new DeviceConfiguration(appId,
-                    segmentRoutingManager.cfgService);
+            deviceConfiguration = new DeviceConfiguration(srManager);
 
-            arpHandler = new ArpHandler(segmentRoutingManager);
-            icmpHandler = new IcmpHandler(segmentRoutingManager);
-            ipHandler = new IpHandler(segmentRoutingManager);
-            routingRulePopulator = new RoutingRulePopulator(segmentRoutingManager);
-            defaultRoutingHandler = new DefaultRoutingHandler(segmentRoutingManager);
+            arpHandler = new ArpHandler(srManager);
+            icmpHandler = new IcmpHandler(srManager);
+            ipHandler = new IpHandler(srManager);
+            routingRulePopulator = new RoutingRulePopulator(srManager);
+            defaultRoutingHandler = new DefaultRoutingHandler(srManager);
 
             tunnelHandler = new TunnelHandler(linkService, deviceConfiguration,
                                               groupHandlerMap, tunnelStore);
diff --git a/src/main/java/org/onosproject/segmentrouting/config/DeviceConfiguration.java b/src/main/java/org/onosproject/segmentrouting/config/DeviceConfiguration.java
index c1af6f2..15e9fa7 100644
--- a/src/main/java/org/onosproject/segmentrouting/config/DeviceConfiguration.java
+++ b/src/main/java/org/onosproject/segmentrouting/config/DeviceConfiguration.java
@@ -23,16 +23,14 @@
 import org.onlab.packet.IpPrefix;
 import org.onlab.packet.MacAddress;
 import org.onlab.packet.VlanId;
-import org.onosproject.core.ApplicationId;
 import org.onosproject.incubator.net.config.basics.ConfigException;
 import org.onosproject.incubator.net.config.basics.InterfaceConfig;
 import org.onosproject.incubator.net.intf.Interface;
 import org.onosproject.net.ConnectPoint;
-import org.onosproject.net.config.NetworkConfigRegistry;
-import org.onosproject.net.config.NetworkConfigService;
 import org.onosproject.net.host.InterfaceIpAddress;
 import org.onosproject.net.DeviceId;
 import org.onosproject.net.PortNumber;
+import org.onosproject.segmentrouting.SegmentRoutingManager;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
@@ -41,9 +39,9 @@
 import java.util.HashSet;
 import java.util.List;
 import java.util.Map;
-import java.util.Optional;
 import java.util.Set;
 import java.util.concurrent.ConcurrentHashMap;
+import java.util.stream.Collectors;
 
 import static com.google.common.base.Preconditions.checkNotNull;
 
@@ -54,11 +52,14 @@
  */
 public class DeviceConfiguration implements DeviceProperties {
 
+    private static final String ERROR_CONFIG = "Configuration error.";
+    private static final String TOO_MANY_SUBNET = ERROR_CONFIG + " Too many subnets configured on {}";
+    private static final String NO_SUBNET = "No subnet configured on {}";
+
     private static final Logger log = LoggerFactory.getLogger(DeviceConfiguration.class);
     private final List<Integer> allSegmentIds = new ArrayList<>();
     private final Map<DeviceId, SegmentRouterInfo> deviceConfigMap = new ConcurrentHashMap<>();
-    private ApplicationId appId;
-    private NetworkConfigService cfgService;
+    private SegmentRoutingManager srManager;
 
     private class SegmentRouterInfo {
         int nodeSid;
@@ -80,20 +81,17 @@
      * Constructs device configuration for all Segment Router devices,
      * organizing the data into various maps for easier access.
      *
-     * @param appId application id
-     * @param cfgService config service
+     * @param srManager Segment Routing Manager
      */
-    public DeviceConfiguration(ApplicationId appId,
-            NetworkConfigRegistry cfgService) {
-        this.appId = appId;
-        this.cfgService = cfgService;
+    public DeviceConfiguration(SegmentRoutingManager srManager) {
+        this.srManager = srManager;
 
         // Read config from device subject, excluding gatewayIps and subnets.
         Set<DeviceId> deviceSubjects =
-                cfgService.getSubjects(DeviceId.class, SegmentRoutingDeviceConfig.class);
+                srManager.cfgService.getSubjects(DeviceId.class, SegmentRoutingDeviceConfig.class);
         deviceSubjects.forEach(subject -> {
             SegmentRoutingDeviceConfig config =
-                cfgService.getConfig(subject, SegmentRoutingDeviceConfig.class);
+                    srManager.cfgService.getConfig(subject, SegmentRoutingDeviceConfig.class);
             SegmentRouterInfo info = new SegmentRouterInfo();
             info.deviceId = subject;
             info.nodeSid = config.nodeSid();
@@ -106,20 +104,12 @@
             allSegmentIds.add(info.nodeSid);
         });
 
-        // Read gatewayIps and subnets from port subject.
-        Set<ConnectPoint> portSubjects =
-            cfgService.getSubjects(ConnectPoint.class, InterfaceConfig.class);
-        portSubjects.forEach(subject -> {
-            // Do not process excluded ports
-            SegmentRoutingAppConfig appConfig =
-                    cfgService.getConfig(appId, SegmentRoutingAppConfig.class);
-            if (appConfig != null && appConfig.suppressSubnet().contains(subject)) {
-                log.info("Ignore suppressed port {}", subject);
-                return;
-            }
-
+        // Read gatewayIps and subnets from port subject. Ignore suppressed ports.
+        Set<ConnectPoint> portSubjects = srManager.cfgService
+                .getSubjects(ConnectPoint.class, InterfaceConfig.class);
+        portSubjects.stream().filter(subject -> !isSuppressedPort(subject)).forEach(subject -> {
             InterfaceConfig config =
-                    cfgService.getConfig(subject, InterfaceConfig.class);
+                    srManager.cfgService.getConfig(subject, InterfaceConfig.class);
             Set<Interface> networkInterfaces;
             try {
                 networkInterfaces = config.getInterfaces();
@@ -343,7 +333,7 @@
             ImmutableSet.Builder<Ip4Prefix> builder = ImmutableSet.builder();
             builder.addAll(srinfo.subnets.values());
             SegmentRoutingAppConfig appConfig =
-                    cfgService.getConfig(appId, SegmentRoutingAppConfig.class);
+                    srManager.cfgService.getConfig(srManager.appId, SegmentRoutingAppConfig.class);
             if (appConfig != null) {
                 if (deviceId.equals(appConfig.vRouterId().orElse(null))) {
                     builder.add(Ip4Prefix.valueOf("0.0.0.0/0"));
@@ -354,25 +344,38 @@
         return null;
     }
 
+
     /**
-     *  Returns the configured non-/32 and non-/0 subnet on the given port,
-     *  or null if no subnet has been configured on the port.
+     * Returns the subnet configuration of given device and port.
      *
-     *  @param deviceId device identifier
-     *  @param pnum  port identifier
-     *  @return configured subnet on port, or null
+     * @param deviceId Device ID
+     * @param port Port number
+     * @return The subnet configured on given port or null if
+     *         the port is unconfigured, misconfigured or suppressed.
      */
-    public Ip4Prefix getPortSubnet(DeviceId deviceId, PortNumber pnum) {
-        SegmentRouterInfo srinfo = deviceConfigMap.get(deviceId);
-        if (srinfo != null) {
-            Optional<Ip4Prefix> result = srinfo.subnets.get(pnum).stream()
-                    .filter(subnet ->
-                            subnet.getIp4Prefix().prefixLength() != IpPrefix.MAX_INET_MASK_LENGTH &&
-                            subnet.getIp4Prefix().prefixLength() != 0)
-                    .findFirst();
-            return (result.isPresent()) ? result.get() : null;
+    public Ip4Prefix getPortSubnet(DeviceId deviceId, PortNumber port) {
+        ConnectPoint connectPoint = new ConnectPoint(deviceId, port);
+
+        if (isSuppressedPort(connectPoint)) {
+            return null;
         }
-        return null;
+
+        Set<Ip4Prefix> subnets =
+                srManager.interfaceService.getInterfacesByPort(connectPoint).stream()
+                        .flatMap(intf -> intf.ipAddressesList().stream())
+                        .map(InterfaceIpAddress::subnetAddress)
+                        .map(IpPrefix::getIp4Prefix)
+                        .collect(Collectors.toSet());
+
+        if (subnets.size() == 0) {
+            log.info(NO_SUBNET, connectPoint);
+            return null;
+        } else if (subnets.size() > 1) {
+            log.warn(TOO_MANY_SUBNET, connectPoint);
+            return null;
+        } else {
+            return subnets.stream().findFirst().orElse(null);
+        }
     }
 
     /**
@@ -504,4 +507,14 @@
         }
         srinfo.subnets.remove(cp.port(), ip4Prefix);
     }
+
+    private boolean isSuppressedPort(ConnectPoint connectPoint) {
+        SegmentRoutingAppConfig appConfig = srManager.cfgService
+                .getConfig(srManager.appId, SegmentRoutingAppConfig.class);
+        if (appConfig != null && appConfig.suppressSubnet().contains(connectPoint)) {
+            log.info("Ignore suppressed port {}", connectPoint);
+            return true;
+        }
+        return false;
+    }
 }