A5000 - diving in at the deep end!

[HigashiJun]

No, that didn't work because the jumpers were set to use the BNC connector. BNC or AUI, I get exactly the same issue. Also, I tested the Centrecom on another device and it worked perfectly, at least as far as I could tell. I may double check it, but they are pretty reliable, and the fact that the problem is the same even with the BNC connector suggests its a software issue.

I should have a LAN TAP soon, I can place that between the cable and the A5000 to see if the SYN/ACK from the Windows server gets to the A5000. I suspect it is as I see it at the mirror port on the switch, but the TAP will be as close to the A5000 as I can get.

Gosh, your network issue seems inextricable...

[rubber_jonnie]

No, that didn't work because the jumpers were set to use the BNC connector. BNC or AUI, I get exactly the same issue. Also, I tested the Centrecom on another device and it worked perfectly, at least as far as I could tell. I may double check it, but they are pretty reliable, and the fact that the problem is the same even with the BNC connector suggests its a software issue.

I should have a LAN TAP soon, I can place that between the cable and the A5000 to see if the SYN/ACK from the Windows server gets to the A5000. I suspect it is as I see it at the mirror port on the switch, but the TAP will be as close to the A5000 as I can get.

Gosh, your network issue seems inextricable...

It's a weird one for sure, but I can use my work problem solving techniques to delve into it, hence the packet captures on the network. Just wish there was a packet capture tool for the A5000.

[HigashiJun]

Just wish there was a packet capture tool for the A5000.

For sure, it would be of great help.

[rubber_jonnie]

Just wish there was a packet capture tool for the A5000.

For sure, it would be of great help.

What I wouldn't give to see inside the TCP/IP stack!!

I have also been trying to set up a telnet client on the A5000, but I don't think it's compatible, and the RISCOS SMB server doesn't work either. I may recap the NIC as a hail Mary, but if I can see the SYN/ACK arrives at the NIC, it can only be an internal HW failure or a software failure.

It's weird that so much else works, like ICMP and UDP. Very odd indeed.

This is what the network traffic looks like at the switchport when I try to make a connection with LanMan98:

Screenshot 2023-11-27 at 10.02.28.png (125.64 KiB) Viewed 1388 times

You can see the SYN from the A5000 (192.168.1.60) to the Windows machine (192.168.1.59). The windows machine sends a SYN/ACK back and is expecting a SYN back from the A5000. It doesn't get the SYN back, so retransmits after 3 seconds, then retransmits again after another 6 seconds.

Despite the Windows machine sending the SYN/ACK 3 times in total, the A5000 behaves like it never saw the SYN/ACKs at all and sends 3 RST packets in rapid succession to close the connection.

I've looked at a lot of packet captures over the years and usually when something like this happens it's a routing issue, but I know the SYN/ACK gets as far as the switch the A5000 is plugged into.

[HigashiJun]

@rubber_jonnie

Really odd...

This doesn't make me feel like fitting a network podule in my A5000 (provided I manage to repair it first).

[rubber_jonnie]

@rubber_jonnie

Really odd...

This doesn't make me feel like fitting a network podule in my A5000 (provided I manage to repair it first).

If you can find a network podule... I think I got the last one from CJE.

On the other hand, if you do, I have covered a lot of ground already

[HigashiJun]

If you can find a network podule... I think I got the last one from CJE.

On the other hand, if you do, I have covered a lot of ground already

That's true...

I just hope you will find a way to make your network functional.

[rubber_jonnie]

If you can find a network podule... I think I got the last one from CJE.

On the other hand, if you do, I have covered a lot of ground already

That's true...

I just hope you will find a way to make your network functional.

I had some other thoughts on testing and tried to connect on various ports (80, 139 and some others) fully expecting a fail, since I was using ports that weren't available. The results were as expected, I see a SYN from my laptop, and a reset directly from the A5000. That's normal behaviour.

So I have downloaded a telnet server for RISCOS and I am going to try and get that running and see if I can connect. Really very odd stuff going on, as that is suggestive that TCP is working fine.

[alexh]

Are you using a switch you've not used before? Does it have a built in firewall? Perhaps it needs disabling?

[rubber_jonnie]

Are you using a switch you've not used before? Does it have a built in firewall? Perhaps it needs disabling?

No, it's my everyday switch and my packet captures show that the SYN/ACK is arriving at the port the A5000 is connected to. There is no firewall and the switch is in daily use with no issues.