Solving the MacOS/Airport/Linksys/PPPoE MTU problem
September 4, 2004
My hardware configuration is a DSL modem connected to a Linksys BEFSX41 connected to an Airport base station (don’t ask why I have two routers, it just happened — the BEFSX41 IS a very capable beast), and the Airport had a manually assigned address behind the Linksys router. The Airport handed out wireless addresses dynamically. Anyone using wireless had to constantly reset their MTU to a smaller value (for some reason, 1464 is what worked) because there is no way in MacOS to permanently set the Airport MTU.
I found a solution. Use DHCP. I changed the Airport to get its address dynamically, and the problems vanished. I set my wireless MTU back to the default (1500), started browsing, read mail, sent mail, and it all worked.
However, at least for now, I am having a hard time accessing printers on the external-to-Airport network. The firewall subnet is 192.168.1.*, the Airport subnet is 10.0.1.*, and the Airport is doing NAT for everything behind it. I think I will eventually figure this out, but for now it is suboptimal. Maybe I could cook something up with an SSH tunnel.