diff --git a/internal/router/client_info.go b/internal/router/client_info.go
index dff4ede..f6a13fb 100644
--- a/internal/router/client_info.go
+++ b/internal/router/client_info.go
@@ -2,6 +2,7 @@ package router
 
 import (
 	"bytes"
+	"io"
 	"log"
 	"net"
 	"os"
@@ -78,10 +79,27 @@ func GetClientInfoByMac(mac string) *ctrld.ClientInfo {
 }
 
 func readClientInfoFile(name string) error {
+	f, err := os.Open(name)
+	if err != nil {
+		return err
+	}
+	defer f.Close()
+	return readClientInfoReader(f)
+
+}
+
+func readClientInfoReader(reader io.Reader) error {
 	r := routerPlatform.Load()
-	return lineread.File(name, func(line []byte) error {
+	return lineread.Reader(reader, func(line []byte) error {
 		fields := bytes.Fields(line)
+		if len(fields) != 5 {
+			return nil
+		}
 		mac := string(fields[1])
+		if _, err := net.ParseMAC(mac); err != nil {
+			// The second field is not a mac, skip.
+			return nil
+		}
 		ip := normalizeIP(string(fields[2]))
 		if net.ParseIP(ip) == nil {
 			log.Printf("invalid ip address entry: %q", ip)
diff --git a/internal/router/client_info_test.go b/internal/router/client_info_test.go
index 13b0648..2b228c2 100644
--- a/internal/router/client_info_test.go
+++ b/internal/router/client_info_test.go
@@ -1,6 +1,11 @@
 package router
 
-import "testing"
+import (
+	"strings"
+	"testing"
+
+	"github.com/Control-D-Inc/ctrld"
+)
 
 func Test_normalizeIP(t *testing.T) {
 	tests := []struct {
@@ -23,3 +28,43 @@ func Test_normalizeIP(t *testing.T) {
 		})
 	}
 }
+
+func Test_readClientInfoReader(t *testing.T) {
+	tests := []struct {
+		name string
+		in   string
+		mac  string
+	}{
+		{
+			"good",
+			`1683329857 e6:20:59:b8:c1:6d 192.168.1.186 * 01:e6:20:59:b8:c1:6d
+`,
+			"e6:20:59:b8:c1:6d",
+		},
+		{
+			"bad seen on UDMdream machine",
+			`1683329857 e6:20:59:b8:c1:6e 192.168.1.111 * 01:e6:20:59:b8:c1:6e
+duid 00:01:00:01:2b:e4:2e:2c:52:52:14:26:dc:1c
+1683322985 117442354 2600:4040:b0e6:b700::111 ASDASD 00:01:00:01:2a:d0:b9:81:00:07:32:4c:1c:07
+`,
+			"e6:20:59:b8:c1:6e",
+		},
+	}
+
+	for _, tc := range tests {
+		t.Run(tc.name, func(t *testing.T) {
+			r := routerPlatform.Load()
+			r.mac.Delete(tc.mac)
+			if err := readClientInfoReader(strings.NewReader(tc.in)); err != nil {
+				t.Errorf("readClientInfoReader() error = %v", err)
+			}
+			info, existed := r.mac.Load(tc.mac)
+			if !existed {
+				t.Error("client info missing")
+			}
+			if ci, ok := info.(*ctrld.ClientInfo); ok && existed && ci.Mac != tc.mac {
+				t.Errorf("mac mismatched, got: %q, want: %q", ci.Mac, tc.mac)
+			}
+		})
+	}
+}