diff --git a/pkg/netutil/isolate_linux.go b/pkg/netutil/isolate_linux.go
new file mode 100644
index 000000000..1a322553b
--- /dev/null
+++ b/pkg/netutil/isolate_linux.go
@@ -0,0 +1,42 @@
+// Copyright 2015 CoreOS, Inc.
+//
+// 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 netutil
+
+import (
+	"fmt"
+	"os/exec"
+)
+
+// DropPort drops all network packets that are received from the given port and sent to the given port.
+func DropPort(port int) error {
+	cmdStr := fmt.Sprintf("sudo iptables -A OUTPUT --destination-port %d -j DROP", port)
+	if _, err := exec.Command("/bin/sh", "-c", cmdStr).Output(); err != nil {
+		return err
+	}
+	cmdStr = fmt.Sprintf("sudo iptables -A INPUT --destination-port %d -j DROP", port)
+	_, err := exec.Command("/bin/sh", "-c", cmdStr).Output()
+	return err
+}
+
+// RecoverPort stops dropping network packets at given port.
+func RecoverPort(port int) error {
+	cmdStr := fmt.Sprintf("sudo iptables -D OUTPUT --destination-port %d -j DROP", port)
+	if _, err := exec.Command("/bin/sh", "-c", cmdStr).Output(); err != nil {
+		return err
+	}
+	cmdStr = fmt.Sprintf("sudo iptables -D INPUT --destination-port %d -j DROP", port)
+	_, err := exec.Command("/bin/sh", "-c", cmdStr).Output()
+	return err
+}
diff --git a/pkg/netutil/isolate_stub.go b/pkg/netutil/isolate_stub.go
new file mode 100644
index 000000000..c8f70f9b6
--- /dev/null
+++ b/pkg/netutil/isolate_stub.go
@@ -0,0 +1,21 @@
+// Copyright 2015 CoreOS, Inc.
+//
+// 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.
+
+// +build !linux
+
+package netutil
+
+func DropPort(port int) error { return nil }
+
+func RecoverPort(port int) error { return nil }
diff --git a/tools/functional-tester/etcd-agent/agent.go b/tools/functional-tester/etcd-agent/agent.go
index d63143ce2..97ab8cf1a 100644
--- a/tools/functional-tester/etcd-agent/agent.go
+++ b/tools/functional-tester/etcd-agent/agent.go
@@ -22,6 +22,7 @@ import (
 	"path"
 	"time"
 
+	"github.com/coreos/etcd/pkg/netutil"
 	"github.com/coreos/etcd/tools/functional-tester/etcd-agent/client"
 )
 
@@ -132,6 +133,14 @@ func (a *Agent) terminate() error {
 	return nil
 }
 
+func (a *Agent) dropPort(port int) error {
+	return netutil.DropPort(port)
+}
+
+func (a *Agent) recoverPort(port int) error {
+	return netutil.RecoverPort(port)
+}
+
 func (a *Agent) status() client.Status {
 	return client.Status{State: a.state}
 }
diff --git a/tools/functional-tester/etcd-agent/client/client.go b/tools/functional-tester/etcd-agent/client/client.go
index ea92f99ea..5e9fe7ad4 100644
--- a/tools/functional-tester/etcd-agent/client/client.go
+++ b/tools/functional-tester/etcd-agent/client/client.go
@@ -34,8 +34,10 @@ type Agent interface {
 	Cleanup() error
 	// Terminate stops the exiting etcd the agent started and removes its data dir.
 	Terminate() error
-	// Isoloate isolates the network of etcd
-	Isolate() error
+	// DropPort drops all network packets at the given port.
+	DropPort(port int) error
+	// RecoverPort stops dropping all network packets at the given port.
+	RecoverPort(port int) error
 	// Status returns the status of etcd on the agent
 	Status() (Status, error)
 }
@@ -83,8 +85,12 @@ func (a *agent) Terminate() error {
 	return a.rpcClient.Call("Agent.RPCTerminate", struct{}{}, nil)
 }
 
-func (a *agent) Isolate() error {
-	panic("not implemented")
+func (a *agent) DropPort(port int) error {
+	return a.rpcClient.Call("Agent.RPCDropPort", port, nil)
+}
+
+func (a *agent) RecoverPort(port int) error {
+	return a.rpcClient.Call("Agent.RPCRecoverPort", port, nil)
 }
 
 func (a *agent) Status() (Status, error) {
diff --git a/tools/functional-tester/etcd-agent/rpc.go b/tools/functional-tester/etcd-agent/rpc.go
index 2910a13ab..32b857587 100644
--- a/tools/functional-tester/etcd-agent/rpc.go
+++ b/tools/functional-tester/etcd-agent/rpc.go
@@ -84,8 +84,22 @@ func (a *Agent) RPCTerminate(args struct{}, reply *struct{}) error {
 	return nil
 }
 
-func (a *Agent) RPCIsolate(args struct{}, reply *struct{}) error {
-	panic("not implemented")
+func (a *Agent) RPCDropPort(port int, reply *struct{}) error {
+	log.Printf("rpc: drop port %d", port)
+	err := a.dropPort(port)
+	if err != nil {
+		log.Println("rpc: error dropping port", err)
+	}
+	return nil
+}
+
+func (a *Agent) RPCRecoverPort(port int, reply *struct{}) error {
+	log.Printf("rpc: recover port %d", port)
+	err := a.recoverPort(port)
+	if err != nil {
+		log.Println("rpc: error recovering port", err)
+	}
+	return nil
 }
 
 func (a *Agent) RPCStatus(args struct{}, status *client.Status) error {
diff --git a/tools/functional-tester/etcd-tester/cluster.go b/tools/functional-tester/etcd-tester/cluster.go
index 0a5d7c25b..947281857 100644
--- a/tools/functional-tester/etcd-tester/cluster.go
+++ b/tools/functional-tester/etcd-tester/cluster.go
@@ -27,6 +27,8 @@ import (
 	"github.com/coreos/etcd/tools/functional-tester/etcd-agent/client"
 )
 
+const peerURLPort = 2380
+
 type cluster struct {
 	agentEndpoints []string
 	datadir        string
@@ -76,7 +78,7 @@ func (c *cluster) Bootstrap() error {
 			return err
 		}
 		clientURLs[i] = fmt.Sprintf("http://%s:2379", host)
-		peerURLs[i] = fmt.Sprintf("http://%s:2380", host)
+		peerURLs[i] = fmt.Sprintf("http://%s:%d", host, peerURLPort)
 
 		members[i] = fmt.Sprintf("%s=%s", names[i], peerURLs[i])
 	}
@@ -196,8 +198,10 @@ func setHealthKey(us []string) error {
 		if err != nil {
 			return err
 		}
+		ctx, cancel := context.WithTimeout(context.Background(), time.Second)
 		kapi := etcdclient.NewKeysAPI(c)
-		_, err = kapi.Set(context.TODO(), "health", "good", nil)
+		_, err = kapi.Set(ctx, "health", "good", nil)
+		cancel()
 		if err != nil {
 			return err
 		}
diff --git a/tools/functional-tester/etcd-tester/failure.go b/tools/functional-tester/etcd-tester/failure.go
index 79efe4c1b..3f4fb5159 100644
--- a/tools/functional-tester/etcd-tester/failure.go
+++ b/tools/functional-tester/etcd-tester/failure.go
@@ -172,3 +172,57 @@ func (f *failureKillOneForLongTime) Recover(c *cluster, round int) error {
 	}
 	return c.WaitHealth()
 }
+
+type failureIsolate struct {
+	description
+}
+
+func newFailureIsolate() *failureIsolate {
+	return &failureIsolate{
+		description: "isolate one member",
+	}
+}
+
+func (f *failureIsolate) Inject(c *cluster, round int) error {
+	i := round % c.Size
+	if err := c.Agents[i].DropPort(peerURLPort); err != nil {
+		return err
+	}
+	return nil
+}
+
+func (f *failureIsolate) Recover(c *cluster, round int) error {
+	i := round % c.Size
+	if err := c.Agents[i].RecoverPort(peerURLPort); err != nil {
+		return err
+	}
+	return c.WaitHealth()
+}
+
+type failureIsolateAll struct {
+	description
+}
+
+func newFailureIsolateAll() *failureIsolateAll {
+	return &failureIsolateAll{
+		description: "isolate all members",
+	}
+}
+
+func (f *failureIsolateAll) Inject(c *cluster, round int) error {
+	for _, a := range c.Agents {
+		if err := a.DropPort(peerURLPort); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+func (f *failureIsolateAll) Recover(c *cluster, round int) error {
+	for _, a := range c.Agents {
+		if err := a.RecoverPort(peerURLPort); err != nil {
+			return err
+		}
+	}
+	return c.WaitHealth()
+}
diff --git a/tools/functional-tester/etcd-tester/main.go b/tools/functional-tester/etcd-tester/main.go
index 35856b81f..4af87bf14 100644
--- a/tools/functional-tester/etcd-tester/main.go
+++ b/tools/functional-tester/etcd-tester/main.go
@@ -40,6 +40,8 @@ func main() {
 			newFailureKillMajority(),
 			newFailureKillOne(),
 			newFailureKillOneForLongTime(),
+			newFailureIsolate(),
+			newFailureIsolateAll(),
 		},
 		cluster: c,
 		limit:   *limit,
diff --git a/tools/functional-tester/etcd-tester/stresser.go b/tools/functional-tester/etcd-tester/stresser.go
index ba2d49f01..dce7931e0 100644
--- a/tools/functional-tester/etcd-tester/stresser.go
+++ b/tools/functional-tester/etcd-tester/stresser.go
@@ -61,8 +61,10 @@ func (s *stresser) Stress() error {
 	for i := 0; i < s.N; i++ {
 		go func() {
 			for {
+				setctx, setcancel := context.WithTimeout(ctx, time.Second)
 				key := fmt.Sprintf("foo%d", rand.Intn(s.KeySuffixRange))
-				_, err := kv.Set(ctx, key, randStr(s.KeySize), nil)
+				_, err := kv.Set(setctx, key, randStr(s.KeySize), nil)
+				setcancel()
 				if err == context.Canceled {
 					return
 				}