diff --git a/apps/pi-demo/ecmp/src/main/java/org/onosproject/pi/demo/app/ecmp/EcmpFabricApp.java b/apps/pi-demo/ecmp/src/main/java/org/onosproject/pi/demo/app/ecmp/EcmpFabricApp.java
new file mode 100644
index 0000000..7caa8e9
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+++ b/apps/pi-demo/ecmp/src/main/java/org/onosproject/pi/demo/app/ecmp/EcmpFabricApp.java
@@ -0,0 +1,275 @@
+/*
+ * Copyright 2017-present Open Networking Foundation
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.onosproject.pi.demo.app.ecmp;
+
+import com.google.common.collect.Lists;
+import com.google.common.collect.Maps;
+import org.apache.commons.lang3.tuple.Pair;
+import org.apache.felix.scr.annotations.Component;
+import org.onlab.util.ImmutableByteSequence;
+import org.onosproject.net.flow.TrafficSelector;
+import org.onosproject.net.flow.criteria.Criterion;
+import org.onosproject.net.flow.criteria.PiCriterion;
+import org.onosproject.net.pi.runtime.PiAction;
+import org.onosproject.net.pi.runtime.PiActionId;
+import org.onosproject.net.pi.runtime.PiActionParam;
+import org.onosproject.net.pi.runtime.PiActionParamId;
+import org.onosproject.net.pi.runtime.PiHeaderFieldId;
+import org.onosproject.net.pi.runtime.PiTableAction;
+import org.onosproject.pi.demo.app.common.AbstractUpgradableFabricApp;
+import org.onosproject.net.DeviceId;
+import org.onosproject.net.Host;
+import org.onosproject.net.Path;
+import org.onosproject.net.Port;
+import org.onosproject.net.PortNumber;
+import org.onosproject.net.flow.DefaultTrafficSelector;
+import org.onosproject.net.flow.DefaultTrafficTreatment;
+import org.onosproject.net.flow.FlowRule;
+import org.onosproject.net.flow.TrafficTreatment;
+import org.onosproject.net.pi.model.DefaultPiPipeconf;
+import org.onosproject.net.pi.model.PiPipeconf;
+import org.onosproject.net.pi.model.PiPipeconfId;
+import org.onosproject.net.pi.model.PiPipelineInterpreter;
+import org.onosproject.net.topology.DefaultTopologyVertex;
+import org.onosproject.net.topology.Topology;
+import org.onosproject.net.topology.TopologyGraph;
+import org.onosproject.bmv2.model.Bmv2PipelineModelParser;
+
+import java.net.URL;
+import java.util.Collection;
+import java.util.Iterator;
+import java.util.List;
+import java.util.Map;
+import java.util.Set;
+import java.util.stream.Collectors;
+
+import static java.util.stream.Collectors.toSet;
+import static org.onlab.packet.EthType.EtherType.IPV4;
+import static org.onosproject.net.pi.model.PiPipeconf.ExtensionType.BMV2_JSON;
+import static org.onosproject.net.pi.model.PiPipeconf.ExtensionType.P4_INFO_TEXT;
+import static org.onosproject.pi.demo.app.ecmp.EcmpInterpreter.*;
+
+
+/**
+ * Implementation of an upgradable fabric app for the ECMP configuration.
+ */
+@Component(immediate = true)
+public class EcmpFabricApp extends AbstractUpgradableFabricApp {
+
+    private static final String APP_NAME = "org.onosproject.pi-ecmp-fabric";
+    private static final String MODEL_NAME = "ECMP";
+    private static final String PIPECONF_ID = "org.project.pipeconf.ecmp";
+    private static final URL P4INFO_URL = EcmpFabricApp.class.getResource("ecmp.p4info");
+    private static final URL JSON_URL = EcmpFabricApp.class.getResource("ecmp.json");
+
+    private static final PiPipeconf ECMP_PIPECONF = DefaultPiPipeconf.builder()
+            .withId(new PiPipeconfId(PIPECONF_ID))
+            .withPipelineModel(Bmv2PipelineModelParser.parse(JSON_URL))
+            .addBehaviour(PiPipelineInterpreter.class, EcmpInterpreter.class)
+            .addExtension(P4_INFO_TEXT, P4INFO_URL)
+            .addExtension(BMV2_JSON, JSON_URL)
+            .build();
+
+    private static final Map<DeviceId, Map<Set<PortNumber>, Short>> DEVICE_GROUP_ID_MAP = Maps.newHashMap();
+
+    public EcmpFabricApp() {
+        super(APP_NAME, MODEL_NAME, ECMP_PIPECONF);
+    }
+
+    @Override
+    public boolean initDevice(DeviceId deviceId) {
+        // Nothing to do.
+        return true;
+    }
+
+    @Override
+    public List<FlowRule> generateLeafRules(DeviceId leaf, Host srcHost, Collection<Host> dstHosts,
+                                            Collection<DeviceId> availableSpines, Topology topo)
+            throws FlowRuleGeneratorException {
+
+        // Get ports which connect this leaf switch to hosts.
+        Set<PortNumber> hostPorts = deviceService.getPorts(leaf)
+                .stream()
+                .filter(port -> !isFabricPort(port, topo))
+                .map(Port::number)
+                .collect(Collectors.toSet());
+
+        // Get ports which connect this leaf to the given available spines.
+        TopologyGraph graph = topologyService.getGraph(topo);
+        Set<PortNumber> fabricPorts = graph.getEdgesFrom(new DefaultTopologyVertex(leaf))
+                .stream()
+                .filter(e -> availableSpines.contains(e.dst().deviceId()))
+                .map(e -> e.link().src().port())
+                .collect(Collectors.toSet());
+
+        if (hostPorts.size() != 1 || fabricPorts.size() == 0) {
+            log.error("Leaf switch has invalid port configuration: hostPorts={}, fabricPorts={}",
+                      hostPorts.size(), fabricPorts.size());
+            throw new FlowRuleGeneratorException();
+        }
+        PortNumber hostPort = hostPorts.iterator().next();
+
+        List<FlowRule> rules = Lists.newArrayList();
+
+        TrafficTreatment treatment;
+        if (fabricPorts.size() > 1) {
+            // Do ECMP.
+            Pair<PiTableAction, List<FlowRule>> result = provisionEcmpPiTableAction(leaf, fabricPorts);
+            rules.addAll(result.getRight());
+            treatment = DefaultTrafficTreatment.builder().piTableAction(result.getLeft()).build();
+        } else {
+            // Output on port.
+            PortNumber outPort = fabricPorts.iterator().next();
+            treatment = DefaultTrafficTreatment.builder().setOutput(outPort).build();
+        }
+
+        // From srHost to dstHosts.
+        for (Host dstHost : dstHosts) {
+            FlowRule rule = flowRuleBuilder(leaf, EcmpInterpreter.TABLE0)
+                    .withSelector(
+                            DefaultTrafficSelector.builder()
+                                    .matchInPort(hostPort)
+                                    .matchEthType(IPV4.ethType().toShort())
+                                    .matchEthSrc(srcHost.mac())
+                                    .matchEthDst(dstHost.mac())
+                                    .build())
+                    .withTreatment(treatment)
+                    .build();
+            rules.add(rule);
+        }
+
+        // From fabric ports to this leaf host.
+        for (PortNumber port : fabricPorts) {
+            FlowRule rule = flowRuleBuilder(leaf, EcmpInterpreter.TABLE0)
+                    .withSelector(
+                            DefaultTrafficSelector.builder()
+                                    .matchInPort(port)
+                                    .matchEthType(IPV4.ethType().toShort())
+                                    .matchEthDst(srcHost.mac())
+                                    .build())
+                    .withTreatment(
+                            DefaultTrafficTreatment.builder()
+                                    .setOutput(hostPort)
+                                    .build())
+                    .build();
+            rules.add(rule);
+        }
+
+        return rules;
+    }
+
+    @Override
+    public List<FlowRule> generateSpineRules(DeviceId deviceId, Collection<Host> dstHosts, Topology topo)
+            throws FlowRuleGeneratorException {
+
+        List<FlowRule> rules = Lists.newArrayList();
+
+        // for each host
+        for (Host dstHost : dstHosts) {
+
+            Set<Path> paths = topologyService.getPaths(topo, deviceId, dstHost.location().deviceId());
+
+            if (paths.size() == 0) {
+                log.warn("Can't find any path between spine {} and host {}", deviceId, dstHost);
+                throw new FlowRuleGeneratorException();
+            }
+
+            TrafficTreatment treatment;
+
+            if (paths.size() == 1) {
+                // Only one path, do output on port.
+                PortNumber port = paths.iterator().next().src().port();
+                treatment = DefaultTrafficTreatment.builder().setOutput(port).build();
+            } else {
+                // Multiple paths, do ECMP.
+                Set<PortNumber> portNumbers = paths.stream().map(p -> p.src().port()).collect(toSet());
+                Pair<PiTableAction, List<FlowRule>> result = provisionEcmpPiTableAction(deviceId, portNumbers);
+                rules.addAll(result.getRight());
+                treatment = DefaultTrafficTreatment.builder().piTableAction(result.getLeft()).build();
+            }
+
+            FlowRule rule = flowRuleBuilder(deviceId, EcmpInterpreter.TABLE0)
+                    .withSelector(
+                            DefaultTrafficSelector.builder()
+                                    .matchEthType(IPV4.ethType().toShort())
+                                    .matchEthDst(dstHost.mac())
+                                    .build())
+                    .withTreatment(treatment)
+                    .build();
+
+            rules.add(rule);
+        }
+
+        return rules;
+    }
+
+    private Pair<PiTableAction, List<FlowRule>> provisionEcmpPiTableAction(DeviceId deviceId,
+                                                                            Set<PortNumber> fabricPorts)
+            throws FlowRuleGeneratorException {
+
+        // Install ECMP group table entries that map from hash values to actual fabric ports...
+        int groupId = groupIdOf(deviceId, fabricPorts);
+        int groupSize = fabricPorts.size();
+        Iterator<PortNumber> portIterator = fabricPorts.iterator();
+        List<FlowRule> rules = Lists.newArrayList();
+        for (short i = 0; i < groupSize; i++) {
+            FlowRule rule = flowRuleBuilder(deviceId, EcmpInterpreter.ECMP_GROUP_TABLE)
+                    .withSelector(
+                            buildEcmpTrafficSelector(groupId, i))
+                    .withTreatment(
+                            DefaultTrafficTreatment.builder()
+                                    .setOutput(portIterator.next())
+                                    .build())
+                    .build();
+            rules.add(rule);
+        }
+
+        PiTableAction piTableAction = buildEcmpPiTableAction(groupId, groupSize);
+
+        return Pair.of(piTableAction, rules);
+    }
+
+    private PiTableAction buildEcmpPiTableAction(int groupId, int groupSize) {
+
+        return PiAction.builder()
+                .withId(PiActionId.of(ECMP_GROUP_ACTION_NAME))
+                .withParameter(new PiActionParam(PiActionParamId.of(GROUP_ID),
+                                                 ImmutableByteSequence.copyFrom(groupId)))
+                .withParameter(new PiActionParam(PiActionParamId.of(GROUP_SIZE),
+                                                 ImmutableByteSequence.copyFrom(groupSize)))
+                .build();
+    }
+
+    private TrafficSelector buildEcmpTrafficSelector(int groupId, int selector) {
+        Criterion ecmpCriterion = PiCriterion.builder()
+                .matchExact(PiHeaderFieldId.of(ECMP_METADATA_HEADER_NAME, GROUP_ID), groupId)
+                .matchExact(PiHeaderFieldId.of(ECMP_METADATA_HEADER_NAME, SELECTOR), selector)
+                .build();
+
+        return DefaultTrafficSelector.builder()
+                .matchPi((PiCriterion) ecmpCriterion)
+                .build();
+    }
+
+    public int groupIdOf(DeviceId deviceId, Set<PortNumber> ports) {
+        DEVICE_GROUP_ID_MAP.putIfAbsent(deviceId, Maps.newHashMap());
+        // Counts the number of unique portNumber sets for each deviceId.
+        // Each distinct set of portNumbers will have a unique ID.
+        return DEVICE_GROUP_ID_MAP.get(deviceId).computeIfAbsent(ports, (pp) ->
+                (short) (DEVICE_GROUP_ID_MAP.get(deviceId).size() + 1));
+    }
+}
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