Ron Beaufort
Lifetime Supporting Member
this is all just about student lab work in a classroom environment - so this isn't really a "problem" for me – but I'm more than a little bit curious ...
when I use Wireshark to "discover" an unknown address on something like a 1756-ENBT it works flawlessly ... and on a 1769-L35E – also perfect results ...
specifically, when I first connect either one of these two devices to a simple network with my laptop, the expected magic happens – and the Wireshark window displays something like this:
that part is great – and now I know the IP address of the "unknown" network device – even if it's on a completely different subnet from my laptop ... so Wireshark works ...
but ...
I can't get the same response from a 1756-ENET ... nothing "Gratuitous" pops up on the Wireshark screen when I connect to one of these things ... (I've tried it with two separate ENETs with the same lousy results) ...
so ...
I'm thinking that the newer ENBT and the also newer L35E devices will make the "Gratuitous" requests as advertised ... but ... it looks like the somewhat older ENET devices don't want to cooperate ... and yes, I can ping these things with ZERO problems ... and they work perfectly with RSLinx and so on ...
is there something simple that I'm missing – or is this just the way the world works? ... I've tried powering-down and powering-up ... and plugging-out and plugging-in ... and the super-secret high-tech rain dance (yes, going counter-clockwise and making sure to lead off with my right foot) ...
as I said earlier, this isn't something that I'm worried about ... if it works OK – and if it doesn't work that's OK too ... but if it's just a matter of some simple little setting that I'm missing, I'd appreciate a kind nudge in the right direction ...
thank you for reading this far ...
when I use Wireshark to "discover" an unknown address on something like a 1756-ENBT it works flawlessly ... and on a 1769-L35E – also perfect results ...
specifically, when I first connect either one of these two devices to a simple network with my laptop, the expected magic happens – and the Wireshark window displays something like this:
Gratuitous ARP for 192.168.1.3 (Request)
that part is great – and now I know the IP address of the "unknown" network device – even if it's on a completely different subnet from my laptop ... so Wireshark works ...
but ...
I can't get the same response from a 1756-ENET ... nothing "Gratuitous" pops up on the Wireshark screen when I connect to one of these things ... (I've tried it with two separate ENETs with the same lousy results) ...
so ...
I'm thinking that the newer ENBT and the also newer L35E devices will make the "Gratuitous" requests as advertised ... but ... it looks like the somewhat older ENET devices don't want to cooperate ... and yes, I can ping these things with ZERO problems ... and they work perfectly with RSLinx and so on ...
is there something simple that I'm missing – or is this just the way the world works? ... I've tried powering-down and powering-up ... and plugging-out and plugging-in ... and the super-secret high-tech rain dance (yes, going counter-clockwise and making sure to lead off with my right foot) ...
as I said earlier, this isn't something that I'm worried about ... if it works OK – and if it doesn't work that's OK too ... but if it's just a matter of some simple little setting that I'm missing, I'd appreciate a kind nudge in the right direction ...
thank you for reading this far ...