diff --git a/board/aarch64/linux_defconfig b/board/aarch64/linux_defconfig
index 7583f6cd..5b267563 100644
--- a/board/aarch64/linux_defconfig
+++ b/board/aarch64/linux_defconfig
@@ -129,6 +129,8 @@ CONFIG_UEVENT_HELPER=y
 CONFIG_UEVENT_HELPER_PATH="/sbin/hotplug"
 CONFIG_DEVTMPFS=y
 CONFIG_DEVTMPFS_MOUNT=y
+CONFIG_FW_CFG_SYSFS=y
+CONFIG_FW_CFG_SYSFS_CMDLINE=y
 CONFIG_MTD=y
 CONFIG_MTD_BLOCK=y
 CONFIG_MTD_BLOCK2MTD=y
diff --git a/board/amd64/linux_defconfig b/board/amd64/linux_defconfig
index 5d1860ff..1f3d8956 100644
--- a/board/amd64/linux_defconfig
+++ b/board/amd64/linux_defconfig
@@ -61,6 +61,8 @@ CONFIG_NET_9P_VIRTIO=y
 CONFIG_PCI=y
 CONFIG_DEVTMPFS=y
 CONFIG_DEVTMPFS_MOUNT=y
+CONFIG_FW_CFG_SYSFS=y
+CONFIG_FW_CFG_SYSFS_CMDLINE=y
 CONFIG_VIRTIO_BLK=y
 CONFIG_BLK_DEV_SD=y
 CONFIG_SCSI_VIRTIO=y
diff --git a/board/common/rootfs/lib/infix/swup b/board/common/rootfs/lib/infix/swup
index 1f7f864d..f2a52bf2 100755
--- a/board/common/rootfs/lib/infix/swup
+++ b/board/common/rootfs/lib/infix/swup
@@ -5,11 +5,14 @@
 ident=$(basename "$0")
 num=0
 
-# Perform any interface renames as dictated by /etc/mactab.
-if [ -f /etc/mactab ]; then
-	logger -k -p user.notice -t "$ident" "calling nameif -c /etc/mactab"
-	nameif -s
-fi
+# Perform any interface renames as dictated by, first, any Qemu
+# override (for testing), and then the user specific /etc/mactab
+for file in /sys/firmware/qemu_fw_cfg/by_name/opt/mactab/raw /etc/mactab; do
+	if [ -f $file ]; then
+		logger -k -p user.notice -t "$ident" "calling nameif -c $file"
+		nameif -c $file -s
+	fi
+done
 
 # Find CPU interfaces used for connecting to a switch managed by DSA
 for netif in /sys/class/net/*; do
@@ -37,3 +40,30 @@ ports=$(devlink port 2>/dev/null | awk '/flavour physical/{print $5}')
 for iface in $ports; do
 	ip link set "$iface" group port
 done
+
+# Testing, e.g., using /etc/mactab may use TAP devices to create
+# emulated switch ports, make sure to mark them as well
+ports=$(ip -json link | jq -r '.[].ifname | match("^e[[:digit:]]+").string')
+for iface in $ports; do
+	ip link set "$iface" group port
+done
+
+# Factory default: all switch ports in VLAN 1 of br0
+# need to check for 'length > 0' because ip command
+# outputs empty json objects for non-port group ifs
+ports=$(ip -json link show group port | jq -r '.[].ifname | select(length > 0)' | tr "\n" " ")
+if [ ! -f /etc/network/interfaces.d/br0 ] && [ -n "$ports" ]; then
+	cat <<-EOF >/etc/network/interfaces.d/br0
+		auto br0
+		iface br0
+		    bridge-ports $ports
+		    bridge-vlan-aware yes
+		    bridge-stp on
+		    bridge-vids 1
+
+		auto vlan1
+		iface vlan1 inet dhcp
+		    vlan-id 1
+		    vlan-raw-device br0
+	EOF
+fi
diff --git a/qemu/qemu.sh b/qemu/qemu.sh
index 2d0c27aa..74be3aa5 100755
--- a/qemu/qemu.sh
+++ b/qemu/qemu.sh
@@ -71,9 +71,13 @@ net_args()
 	echo -n "-nic bridge,br=$QEMU_NET_BRIDGE_DEV,model=$QEMU_NET_MODEL "
     elif [ "$QEMU_NET_TAP" = "y" ]; then
 	QEMU_NET_TAP_N=${QEMU_NET_TAP_N:-1}
+	mactab=$(dirname "$QEMU_ROOTFS")/mactab
+	rm "$mactab"
 	for i in $(seq 0 $(($QEMU_NET_TAP_N - 1))); do
-	    echo -n "-nic tap,ifname=qtap$i,script=no,model=$QEMU_NET_MODEL "
+		echo "e$i	52:54:00:12:34:$((56 + i))" >>"$mactab"
+		echo -n "-nic tap,ifname=qtap$i,script=no,model=$QEMU_NET_MODEL "
 	done
+	echo -n "-fw_cfg name=opt/mactab,file="$mactab" "
     elif [ "$QEMU_NET_USER" = "y" ]; then
 	[ "$QEMU_NET_USER_OPTS" ] && QEMU_NET_USER_OPTS="$QEMU_NET_USER_OPTS,"