MT7620 switch issue

For Developers
#1

When ZBTWE826 is booting, all of its ports are in the switch and in u-boot communication between each devices connected to the switch is allowed.

This behavior is undesirable in many scenarios. For example:

ISP provider -> ZBT - WAN port -> PC in one of LAN

ISP provider offers IP address over DHCP server. ZBT WAN Port is configured as DHCP client.
ZBT provides its own subnet with DHCP server
and PC is set to obtain IP from DHCP client.

The issue become, when ZBT goes into reboot.

PC lost its link (ethernet ports are for few seconds without "energy"), and Windows and many other Operating Systems forget own ethernet settings because of Link Down. They are immediately sending broadcast with DHCP request after link up. Because ZBT is not up yet and its ports are in the switch, the reply is returned from ISP router over ZBT to PC.

It is possible to rework u-boot for "Port Isolate?" Prohibit communication between swtich ports?

#2

I noticed that too. According to the readme that came with the Uboot source I used for an MT7628 (same source for multiple MT chipsets), this "feature" is specially enabled for OpenWRT or Pandorabox. It is disabled by default.

I used the Uboot code that came with the Padavan builds to update a RSA locked Mercury Router, but my ISP uses PPPoE, so no direct problem.

You need to create your own Uboot, but most likely your ZBT has the pandorabox modified Uboot with the web (http) recovery options, so you need to add that feature to the Uboot code.

Maybe @pepe2k could help us out.

#3

I asked my supplier of ZBT (direct contact in ZBTLINK). Maybe they do it too :slight_smile: I ask him for source then.

#4

I've got source of u-boot. I dont know, if it is needed, but see bellow. Maybe is prepared for 32MB Flash.