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 Post subject: getting a TpLink Switch back to life
PostPosted: June 5th, 2021, 18:52 
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Joined: October 3rd, 2005, 0:40
Posts: 3580
Location: Hungary
Hello folks,

long story short: i need an arbitrary config backup for a TL-SG3424 switch, if anybody uses this model, i would be grateful for a config file.

long story long:

my TpLink switch (TL-SG3424) packed up yesterday and i spent some time analyzing it a bit with the following results:
- the initial problem was that the first 16 ports are completely dead, ports 17-24 showed some signs of life at least. System LED remains off (it should be blinking normally).
- supply voltages are fine, stable, not a dried out caps issue
- i got a serial port attached to it and checked what it spits out there. It wasn't much, initially it just displayed a msg to press ctrl-B to enter bootUtil and a word about starting the fw
- i entered boot util and found there are some commands to reset config and update fw.
- first i tried resetting config and it failed in a similar way as this: https://community.spiceworks.com/topic/2287393-tp-link-tl-sg3424-factory-reset-problem
- i also downloaded various FW versions from tplink site and updated the fw through ftp. This was done through port 1, so the initial deadness of these ports is probably due to lack of config, not a hw problem.
- tried to attach jtagulator to its jtag port, which seemed the easiest way of detecting if that port is alive. The pcb layout matches pretty well with MIPS EJTAG connector pinout btw : http://www.t-es-t.hu/download/mips/md00047f.pdf
- jtagulator found nothing, which means to me that the port is disabled in some way.
- I tested jtagulator with a TL-WR1043ND, which has the same jtag layout albeit for a through hole connector. This worked OK, the pinout was identified correctly, matching the linked document.
- i removed the heat sink, which revealed a BCM53314 MCU and some more resistors but could not identify anything that would have enabled the JTAG port.
- i found a way to help it through its main problem by shorting certain flash pins at certain moment, so the fw starts up, but the config was pretty much missing (IP address was unconfigured, interfaces too and a couple of other things).
- I did an initial config to set up ip address to be able to transfer config to a pc and back. The config file i got is pretty weak, it had 4094 dummy VLAN entries and some for the ports but that was more or less everything it had. I removed the vlan entries and downloaded it back to the switch, which helped it init faster but still needing my gestures with the tweezer :)

- at this point i would be really curious to see a working config file and compare, if anybody could send me one. It can be backed up from the web interface as well, no need to mess with the CLI if one's feeling uncomfortable with it.
- also interested in getting that jtag port working... but i believe this is gonna be a bit harder.

thanks a bunch,
pepe

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 Post subject: Re: getting a TpLink Switch back to life
PostPosted: June 6th, 2021, 7:49 
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Joined: May 13th, 2010, 11:17
Posts: 2717
Location: Kuwait
pepe, have you tried the Console Cable? RS-232 to eth (image attached)

with this cable you will be able to access the device booting and start repairing the unit

Note: some devices such as Cisco are using special pin parameters, not sure about the TP-Link


Attachments:
IMG_20210606_144303.jpg
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 Post subject: Re: getting a TpLink Switch back to life
PostPosted: June 6th, 2021, 16:13 
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Joined: October 3rd, 2005, 0:40
Posts: 3580
Location: Hungary
i hooked up a n usb-ttl serial adapter to behind the ttl-rs232 converter (similar to MAX232) and did the above hacking through that. Almost the same as your cable, just a bit more simple (to me, in this situation, when the pcb is unmounted from the chassis).

pepe

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 Post subject: Re: getting a TpLink Switch back to life
PostPosted: June 7th, 2021, 4:30 
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Joined: May 13th, 2010, 11:17
Posts: 2717
Location: Kuwait
what kind of config you are looking for? the default switch you mean?

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 Post subject: Re: getting a TpLink Switch back to life
PostPosted: June 7th, 2021, 18:05 
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Joined: October 3rd, 2005, 0:40
Posts: 3580
Location: Hungary
there is an option to back up current config on a working switch, i need such a config backup file. coz the factory reset does not restore mine in a usable state, in fact, i think the factory config is damaged/erased/corrupt.

Nobody uses this model of switch? :)

pepe

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 Post subject: Re: getting a TpLink Switch back to life
PostPosted: June 13th, 2021, 16:31 
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Joined: September 17th, 2016, 16:06
Posts: 296
Location: India
Wouldn't a full firmware restore do?
Does DDWRT has anything with the kind of switch you have?

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