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ARP cache flushing (or deleting item)

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ARP cache flushing (or deleting item)

Postby Pilotek » Wed Jan 18, 2012 9:56 am

Hello,
please is there some possibility to manipulate (e.g. flush) ARP cache in QNX4.25?

Reason: We want to switch (by software) to another NIC (hot NIC/standby NIC connected to two switches) in PLC in case of lost communication requests (cabling broken, switch failed...) from SCADA PC.
So we would have the same IP address, but another physical (MAC) address and we would face "ARP cache" problem.
Pilotek
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Re: ARP cache flushing (or deleting item)

Postby maschoen » Thu Jan 19, 2012 7:28 am

How about stopping and restarting TCP/IP completely?
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Re: ARP cache flushing (or deleting item)

Postby Pilotek » Thu Jan 19, 2012 11:04 am

Thank you maschoen, maybe we don't need to manipulate ARP cache:
After first experiments with hot/standby NIC-"software switching" (same IP, other MAC) in the PLC our programmer says that communication (requests for data from our QNX4 SCADA system) continues OK after some seconds from NIC swapping.

It seems that ARP protocol is so "wise", that refreshes ARP caches after every change on the network? Further experiments will show...

Further experiments have shown :( SCADA system's requests starts to come on "new" (switched to, former standby) NIC of PLC, but PLC answers to the original (previous hot) NIC. It seems to be a mistake in PLC's OS. Well, we wanted to use some non-documented functions of PLC...
Pilotek
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