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Could a GS748T kill a GS308e??
OK, this one is strange (to me). I thought all was going swimmingly with my new GS748Tv5... I even successfully changed the management VLAN after a heart-stopping pause. (It wouldn't talk to port...
I think I've solved this one. (Obviously) I can't be certain exactly what caused this...
(Background: my gs308e was working perfectly a few days ago. I logged in and recorded (manually) a few configuration parameters.)
Here's what I discovered through careful testing:
1) The gs308e no longer is willing to talk to modern browsers. AFAIK I didn't change anything. And the firmware is not new either. On a hunch, I tried a bunch of browsers...
2) It WILL talk to old IE, Internet Explorer. Unfortunately, my copy won't just open... now Microsoft Edge has mangled it and forces me to MS edge... and they claim I just need to use the built in "IE Mode" button.
3) IE Mode button doesn't exist. But google has an addon, "Legacy Browser Support for IE Mode in Edge". Install that. It works when you load the switch UI with this enabled!
4) Switch then complained about a bad password?!! Oh no... switch had fully reset itself!
Well, at least I have the switch back 😉
schumaku wrote:The known operational (design) issue...
Some call it a bug... some a "missing feature" 😉 As we both know, they don't just revert to the default IP. Even though configured for DHCP, they no longer, EVER, check for a DHCP server.
😄
PapaPeteH wrote:
As we both know, they don't just revert to the default IP.
What then? If the Plus switches are kept up running, if the DHCP servers are kept operational, not much can go wrong.
PapaPeteH wrote:
Even though configured for DHCP, they no longer, EVER, check for a DHCP server.
When these devices cold boot, and are configured for DHCP, an IP config is applied from the DHCP.
The problem does start if the DHCP is not ready, or does not come up e.g. following a power failure. Then the design (good or bad) is to fallback on the default IP - what is for the obvious reasons never lead to workable results. It's correct, the DHCP does not retry to get an IP config. There would be room to enhance - in case the resource situation on the tiny 8051-core does allow.
Alternate approach would be to push a static configured IP config.
I'm sure an 8051 can handle an occasional retry. In fact, it's already doing a retry during basic DHCP. (I go back a LONG way. It's amazing what could be coded in 64kb on an F8 😄 )
In our location (Colorado), and during various instabilities, it's quite possible for DHCP to become unavailable for a time. It's simply painful when some devices go offline -- no longer visible to the configured network.
Yes, once static IP is in place, you're ok... until (as in this case) the device decides to do a factory reset. Combine factory reset with no DHCP for a period of time... and the only solution is a physical visit. 😞
schumaku wrote:What then? If the Plus switches are kept up running, if the DHCP servers are kept operational, not much can go wrong.
In other words, the firmware nicely handles the normal case... but not edge / anomaly cases (which means an attacker can also take advantage.)
At this point, I found a workaround for my edge case. I don't have time to dig in deeper. Learned a lesson about fragility of the firmware I'm dealing with.
I'm not surprised: most coders have a very hard time thinking outside the box of their expected use cases. Anything from simple user error to deviousness can break all kinds of systems. That's why I got paid a lot of $$ to break SW/FW/HW... I'm pretty good at coming up with scenarios that will break anything 😄
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