diff --git a/prog/weaveproxy/main.go b/prog/weaveproxy/main.go
index 58dd29bc..78be8f28 100644
--- a/prog/weaveproxy/main.go
+++ b/prog/weaveproxy/main.go
@@ -12,16 +12,21 @@ import (
 )
 
 var (
-	version           = "(unreleased version)"
-	defaultDockerHost = "unix:///var/run/docker.sock"
-	defaultProcPath   = "/proc"
+	version = "(unreleased version)"
 )
 
+func getenv(key, defaultVal string) string {
+	if v := os.Getenv(key); v != "" {
+		return v
+	}
+	return defaultVal
+}
+
 func main() {
 	var (
 		justVersion bool
 		logLevel    = "info"
-		c           = proxy.Config{Image: "weaveworks/weaveexec"}
+		c           proxy.Config
 		withDNS     bool
 	)
 
@@ -53,10 +58,6 @@ func main() {
 
 	SetLogLevel(logLevel)
 
-	if image := os.Getenv("EXEC_IMAGE"); image != "" {
-		c.Image = image
-	}
-
 	Log.Infoln("weave proxy", version)
 	Log.Infoln("Command line arguments:", strings.Join(os.Args[1:], " "))
 
@@ -64,15 +65,10 @@ func main() {
 		Log.Warning("--with-dns option has been removed; DNS is on by default")
 	}
 
-	c.DockerHost = defaultDockerHost
-	if dockerHost := os.Getenv("DOCKER_HOST"); dockerHost != "" {
-		c.DockerHost = dockerHost
-	}
-
-	c.ProcPath = defaultProcPath
-	if procPath := os.Getenv("PROCFS"); procPath != "" {
-		c.ProcPath = procPath
-	}
+	c.Image = getenv("EXEC_IMAGE", "weaveworks/weaveexec")
+	c.DockerBridge = getenv("DOCKER_BRIDGE", "docker0")
+	c.DockerHost = getenv("DOCKER_HOST", "unix:///var/run/docker.sock")
+	c.ProcPath = getenv("PROCFS", "/proc")
 
 	p, err := proxy.NewProxy(c)
 	if err != nil {
diff --git a/proxy/common.go b/proxy/common.go
index 8903f60e..0bc2b28a 100644
--- a/proxy/common.go
+++ b/proxy/common.go
@@ -36,7 +36,6 @@ func callWeave(args ...string) ([]byte, []byte, error) {
 		}
 	}
 
-	propagateEnv("DOCKER_BRIDGE")
 	propagateEnv("DOCKER_HOST")
 
 	// Propagate WEAVE_DEBUG, to make debugging easier.
diff --git a/proxy/proxy.go b/proxy/proxy.go
index c86f6c45..d8b3cad6 100644
--- a/proxy/proxy.go
+++ b/proxy/proxy.go
@@ -62,6 +62,7 @@ type Config struct {
 	Version             string
 	WithoutDNS          bool
 	NoMulticastRoute    bool
+	DockerBridge        string
 	DockerHost          string
 	ProcPath            string
 }
@@ -152,11 +153,14 @@ func NewProxy(c Config) (*Proxy, error) {
 	p.client = client.Client
 
 	if !p.WithoutDNS {
-		dockerBridgeIP, stderr, err := callWeave("docker-bridge-ip")
+		netDevs, err := GetBridgeNetDev(c.ProcPath, c.DockerBridge)
 		if err != nil {
-			return nil, fmt.Errorf(string(stderr))
+			return nil, err
 		}
-		p.dockerBridgeIP = string(dockerBridgeIP)
+		if len(netDevs) != 1 || len(netDevs[0].CIDRs) != 1 {
+			return nil, fmt.Errorf("Could not obtain address of %s", c.DockerBridge)
+		}
+		p.dockerBridgeIP = netDevs[0].CIDRs[0].IP.String()
 	}
 
 	p.hostnameMatchRegexp, err = regexp.Compile(c.HostnameMatch)