diff --git a/tstest/natlab/vnet/conf.go b/tstest/natlab/vnet/conf.go
index 090800f84..4c8810998 100644
--- a/tstest/natlab/vnet/conf.go
+++ b/tstest/natlab/vnet/conf.go
@@ -196,11 +196,14 @@ func (s *Server) initFromConfig(c *Config) error {
 		if err != nil {
 			return err
 		}
+		nw, err := pcapgo.NewNgWriter(pcf, layers.LinkTypeEthernet)
+		if err != nil {
+			return err
+		}
 		pw := &pcapWriter{
 			f: pcf,
-			w: pcapgo.NewWriter(pcf),
+			w: nw,
 		}
-		pw.w.WriteFileHeader(65536, layers.LinkTypeEthernet)
 		s.pcapWriter = pw
 	}
 	for _, conf := range c.networks {
@@ -235,6 +238,12 @@ func (s *Server) initFromConfig(c *Config) error {
 			id:  i + 1,
 			net: netOfConf[conf.Network()],
 		}
+		if s.pcapWriter != nil {
+			s.pcapWriter.w.AddInterface(pcapgo.NgInterface{
+				Name:     fmt.Sprintf("node%d", n.id),
+				LinkType: layers.LinkTypeEthernet,
+			})
+		}
 		conf.n = n
 		if _, ok := s.nodeByMAC[n.mac]; ok {
 			return fmt.Errorf("two nodes have the same MAC %v", n.mac)
diff --git a/tstest/natlab/vnet/pcap.go b/tstest/natlab/vnet/pcap.go
index 6ac616e86..eb8c2ed3c 100644
--- a/tstest/natlab/vnet/pcap.go
+++ b/tstest/natlab/vnet/pcap.go
@@ -1,6 +1,7 @@
 package vnet
 
 import (
+	"io"
 	"os"
 	"sync"
 
@@ -12,15 +13,24 @@ type pcapWriter struct {
 	f *os.File
 
 	mu sync.Mutex
-	w  *pcapgo.Writer
+	w  *pcapgo.NgWriter
 }
 
 func (p *pcapWriter) WritePacket(ci gopacket.CaptureInfo, data []byte) error {
 	p.mu.Lock()
 	defer p.mu.Unlock()
+	if p.w == nil {
+		return io.ErrClosedPipe
+	}
 	return p.w.WritePacket(ci, data)
 }
 
 func (p *pcapWriter) Close() error {
+	p.mu.Lock()
+	defer p.mu.Unlock()
+	if p.w != nil {
+		p.w.Flush()
+		p.w = nil
+	}
 	return p.f.Close()
 }
diff --git a/tstest/natlab/vnet/vnet.go b/tstest/natlab/vnet/vnet.go
index beeb8da0e..8fe2a9ec1 100644
--- a/tstest/natlab/vnet/vnet.go
+++ b/tstest/natlab/vnet/vnet.go
@@ -568,7 +568,7 @@ func New(c *Config) (*Server, error) {
 }
 
 func (s *Server) Close() {
-	if !s.shuttingDown.Swap(true) {
+	if shutdown := s.shuttingDown.Swap(true); !shutdown {
 		s.shutdownCancel()
 		if s.pcapWriter != nil {
 			s.pcapWriter.Close()