AETHER-3411 Persist network config across reboot

Change-Id: I295f55eeeab957189e151e1b746c9b856a1aac30
diff --git a/systemd/aiab-ue-nat.service b/systemd/aiab-ue-nat.service
new file mode 100644
index 0000000..61364e3
--- /dev/null
+++ b/systemd/aiab-ue-nat.service
@@ -0,0 +1,9 @@
+# Copyright 2022-present Open Networking Foundation
+# SPDX-License-Identifier: Apache-2.0
+
+[Service]
+Type=oneshot
+ExecStart=/bin/bash -c "sudo iptables -t nat -C POSTROUTING -s 172.250.0.0/16 -o DATA_IFACE -j MASQUERADE || sudo iptables -t nat -A POSTROUTING -s 172.250.0.0/16 -o DATA_IFACE -j MASQUERADE"
+
+[Install]
+WantedBy=sys-subsystem-net-devices-core.device