kurogeek
e1e18dd9f3
Neither regression fixed by the previous commit was observable: the VM test had no staging port, and pinging the ISP's PPPoE address only needs ppp0's connected route, not the default route pppd refused to install. Add a fifth node, `oldlan`: a networkd DHCP server on vlan 4 handing gw its staging lease, with a second address (203.0.113.1) that gw can only reach through that lease's default route. It has no route back to the VLANs, so client pings only work if gw masquerades. Proven: pppd's metric-0 default wins over the DHCP one while ppp0 is up; lan reaches the old LAN via the staging port and iot (allowWan = false) does not; after stopping pppd the staging route carries WAN traffic with the same allowWan split; restarting pppd makes ppp0 preferred again.