diff --git a/build.sh b/build.sh
index 36854f8..54edf04 100755
--- a/build.sh
+++ b/build.sh
@@ -332,6 +332,11 @@ apply_patch '06-dhcp-server.diff'
 install -d                                          "$ROOTFS_DIR/etc/dhcp/dhcpd.conf.d/"
 install -m 644 files/dhcpd.conf.d/192.168.82.0.conf "$ROOTFS_DIR/etc/dhcp/dhcpd.conf.d/"
 
+##
+# IP forwarding.
+#
+apply_patch '07-ipv4-forwarding.diff'
+
 ##
 # Unmount virtual file systems.
 #
diff --git a/patches/07-ipv4-forwarding.diff b/patches/07-ipv4-forwarding.diff
new file mode 100644
index 0000000..8da8cd6
--- /dev/null
+++ b/patches/07-ipv4-forwarding.diff
@@ -0,0 +1,11 @@
+--- rootfs.orig/etc/sysctl.conf
++++ rootfs/etc/sysctl.conf
+@@ -25,7 +25,7 @@
+ #net.ipv4.tcp_syncookies=1
+ 
+ # Uncomment the next line to enable packet forwarding for IPv4
+-#net.ipv4.ip_forward=1
++net.ipv4.ip_forward=1
+ 
+ # Uncomment the next line to enable packet forwarding for IPv6
+ #  Enabling this option disables Stateless Address Autoconfiguration
diff --git a/patches/series b/patches/series
index 9f6463a..fb9ef17 100644
--- a/patches/series
+++ b/patches/series
@@ -4,3 +4,4 @@
 04-swap.diff
 05-path.diff
 06-dhcp-server.diff
+07-ipv4-forwarding.diff