Hi heper. Here's the full timeline:
1. about 2 weeks ago I downloaded the CD .iso and tried to install it on my old mini-ITX system. This was a Via EPIA 800 with 512MB RAM and a 2GB CF card, that has been sat unused in my garage for the past 4 years.
2. I was able to install it on the CF card but I had to disable DMA on all IDE ports. I also found that I had to manually create the default route after every reboot. I was suspicious that it was because my system was so ancient (I bought it in ~2002) so I decided to upgrade it.
3. I ordered some replacement hardware for my mini-ITX case: an Intel Atom board with dual gigabit Ethernet (D2500CC), 4GB RAM, and a new USB flash stick to boot it off
4. I got all of that set up today and again found that the default route wasn't added. That's when I posted my original message - I assumed it was the same as when I ran with the original board, i.e. it would lose the gateway on every boot
5. After posting the message, I configured /tmp and /var to be on ramdisks using the UI, and rebooted. I expected to have to log in again and create the default route, but in fact it has added it automatically. So this must be either because it needed a reboot after first configuring the PPPoE connection (and I didn't do it), or it saved the default route I manually added and restored it automatically on boot.