TCPnet DHCP renewal

I have a question about what to do if the ethernet link goes down (eg someone pulled the cable out) while TCPnet is running.

It mostly seems to be fine in that the ethernet traffic resumes if the same cable is replaced. However, my understanding is that if DHCP has been used to obtain an IP address, then the DHCP should be used to renew the lease when the link comes back up, which TCPnet does not do.

TCPnet seems to assume the old IP address is still OK. It *probably* will be if it is reconnected to the same network, but almost certainly won't be if it is connected to a different network.

I can't find a way of forcing the correct behaviour through the API.

Comments?

Christopher Hicks
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  • "TCPnet seems to assume the old IP address is still OK."

    That would be correct - The IP address has been given to the device by the DHCP server for the duration of the lease.

    If the device were disconnected when the lease expired, then it would have to acquire a new lease on re-connection.

    But, in fact, the cable would have to be disconnected for more than half of the trailing time of the lease, because the device should attempt to re-new at 50% of the lease time.

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  • "TCPnet seems to assume the old IP address is still OK."

    That would be correct - The IP address has been given to the device by the DHCP server for the duration of the lease.

    If the device were disconnected when the lease expired, then it would have to acquire a new lease on re-connection.

    But, in fact, the cable would have to be disconnected for more than half of the trailing time of the lease, because the device should attempt to re-new at 50% of the lease time.

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