diff --git a/app/origin_host.go b/app/origin_host.go
index 3a5cdfd3b..03e7921aa 100644
--- a/app/origin_host.go
+++ b/app/origin_host.go
@@ -30,7 +30,7 @@ func getOriginHost(t report.Topology, nodeID string) (OriginHost, bool) {
 	return OriginHost{
 		Hostname: h.Metadata[host.HostName],
 		OS:       h.Metadata[host.OS],
-		Networks: strings.Split(h.Metadata[host.LocalNetworks], " "),
+		Networks: h.Sets[host.LocalNetworks],
 		Load:     h.Metadata[host.Load],
 	}, true
 }
diff --git a/probe/host/reporter.go b/probe/host/reporter.go
index c0226f011..ab4ca9249 100644
--- a/probe/host/reporter.go
+++ b/probe/host/reporter.go
@@ -2,7 +2,6 @@ package host
 
 import (
 	"runtime"
-	"strings"
 	"time"
 
 	"github.com/weaveworks/scope/report"
@@ -71,11 +70,12 @@ func (r *Reporter) Report() (report.Report, error) {
 	rep.Host.AddNode(report.MakeHostNodeID(r.hostID), report.MakeNodeWith(map[string]string{
 		Timestamp:     Now(),
 		HostName:      r.hostName,
-		LocalNetworks: strings.Join(localCIDRs, " "),
 		OS:            runtime.GOOS,
 		Load:          GetLoad(),
 		KernelVersion: kernel,
 		Uptime:        uptime.String(),
+	}).WithSets(report.Sets{
+		LocalNetworks: report.MakeStringSet(localCIDRs...),
 	}))
 
 	return rep, nil
diff --git a/probe/host/reporter_test.go b/probe/host/reporter_test.go
index d41d47e47..48529294b 100644
--- a/probe/host/reporter_test.go
+++ b/probe/host/reporter_test.go
@@ -48,11 +48,12 @@ func TestReporter(t *testing.T) {
 	want.Host.AddNode(report.MakeHostNodeID(hostID), report.MakeNodeWith(map[string]string{
 		host.Timestamp:     now,
 		host.HostName:      hostname,
-		host.LocalNetworks: network,
 		host.OS:            runtime.GOOS,
 		host.Load:          load,
 		host.Uptime:        uptime,
 		host.KernelVersion: kernel,
+	}).WithSets(report.Sets{
+		host.LocalNetworks: report.MakeStringSet(network),
 	}))
 	have, _ := host.NewReporter(hostID, hostname, localNets).Report()
 	if !reflect.DeepEqual(want, have) {
diff --git a/render/short_lived_connections_test.go b/render/short_lived_connections_test.go
index 7461a5bd5..8f36c9507 100644
--- a/render/short_lived_connections_test.go
+++ b/render/short_lived_connections_test.go
@@ -7,6 +7,7 @@ import (
 
 	"github.com/weaveworks/scope/probe/docker"
 	"github.com/weaveworks/scope/probe/endpoint"
+	"github.com/weaveworks/scope/probe/host"
 	"github.com/weaveworks/scope/render"
 	"github.com/weaveworks/scope/report"
 	"github.com/weaveworks/scope/test"
@@ -48,9 +49,9 @@ var (
 		Container: report.Topology{
 			Nodes: report.Nodes{
 				containerNodeID: report.MakeNode().WithMetadata(map[string]string{
-					docker.ContainerID:    containerID,
-					docker.ContainerName:  containerName,
-					report.HostNodeID:     serverHostNodeID,
+					docker.ContainerID:   containerID,
+					docker.ContainerName: containerName,
+					report.HostNodeID:    serverHostNodeID,
 				}).WithSets(report.Sets{
 					docker.ContainerIPs:   report.MakeStringSet(containerIP),
 					docker.ContainerPorts: report.MakeStringSet(fmt.Sprintf("%s:%s->%s/tcp", serverIP, serverPort, serverPort)),
@@ -60,8 +61,9 @@ var (
 		Host: report.Topology{
 			Nodes: report.Nodes{
 				serverHostNodeID: report.MakeNodeWith(map[string]string{
-					"local_networks":  "192.168.0.0/16",
 					report.HostNodeID: serverHostNodeID,
+				}).WithSets(report.Sets{
+					host.LocalNetworks: report.MakeStringSet("192.168.0.0/16"),
 				}),
 			},
 		},
diff --git a/render/theinternet.go b/render/theinternet.go
index 4dc291381..4e67bb820 100644
--- a/render/theinternet.go
+++ b/render/theinternet.go
@@ -2,7 +2,6 @@ package render
 
 import (
 	"net"
-	"strings"
 
 	"github.com/weaveworks/scope/probe/host"
 	"github.com/weaveworks/scope/report"
@@ -19,11 +18,7 @@ func LocalNetworks(r report.Report) report.Networks {
 	)
 
 	for _, md := range r.Host.Nodes {
-		val, ok := md.Metadata[host.LocalNetworks]
-		if !ok {
-			continue
-		}
-		for _, s := range strings.Fields(val) {
+		for _, s := range md.Sets[host.LocalNetworks] {
 			_, ipNet, err := net.ParseCIDR(s)
 			if err != nil {
 				continue
diff --git a/render/theinternet_test.go b/render/theinternet_test.go
index 6d5744d0d..9abfdcb1f 100644
--- a/render/theinternet_test.go
+++ b/render/theinternet_test.go
@@ -16,8 +16,9 @@ func TestReportLocalNetworks(t *testing.T) {
 		Host: report.Topology{
 			Nodes: report.Nodes{
 				"nonets": report.MakeNode(),
-				"foo": report.MakeNodeWith(map[string]string{
-					host.LocalNetworks: "10.0.0.1/8 192.168.1.1/24 10.0.0.1/8 badnet/33",
+				"foo": report.MakeNode().WithSets(report.Sets{
+					host.LocalNetworks: report.MakeStringSet(
+						"10.0.0.1/8", "192.168.1.1/24", "10.0.0.1/8", "badnet/33"),
 				}),
 			},
 		},
diff --git a/test/fixture/report_fixture.go b/test/fixture/report_fixture.go
index 7e09d5a88..15b2aab6a 100644
--- a/test/fixture/report_fixture.go
+++ b/test/fixture/report_fixture.go
@@ -5,6 +5,7 @@ import (
 
 	"github.com/weaveworks/scope/probe/docker"
 	"github.com/weaveworks/scope/probe/endpoint"
+	"github.com/weaveworks/scope/probe/host"
 	"github.com/weaveworks/scope/probe/kubernetes"
 	"github.com/weaveworks/scope/probe/process"
 	"github.com/weaveworks/scope/render"
@@ -282,17 +283,19 @@ var (
 			Nodes: report.Nodes{
 				ClientHostNodeID: report.MakeNodeWith(map[string]string{
 					"host_name":       ClientHostName,
-					"local_networks":  "10.10.10.0/24",
 					"os":              "Linux",
 					"load":            "0.01 0.01 0.01",
 					report.HostNodeID: ClientHostNodeID,
+				}).WithSets(report.Sets{
+					host.LocalNetworks: report.MakeStringSet("10.10.10.0/24"),
 				}),
 				ServerHostNodeID: report.MakeNodeWith(map[string]string{
 					"host_name":       ServerHostName,
-					"local_networks":  "10.10.10.0/24",
 					"os":              "Linux",
 					"load":            "0.01 0.01 0.01",
 					report.HostNodeID: ServerHostNodeID,
+				}).WithSets(report.Sets{
+					host.LocalNetworks: report.MakeStringSet("10.10.10.0/24"),
 				}),
 			},
 		},