dhcpcd-discuss

On 17/08/2020 18:07, shamli badole wrote:
> Hi Roy,
>
> Using dhcpcd 7.0.0.
>
> A router is configured for DHCP on eth1. When the WAN connection is switched 
> from one network to another, TIMEOUT event is observed after it tries to renew 
> the currently assigned lease.
> After TIMEOUT a DHCP DISCOVER is sent. To which an ip is offered from another 
> server.
> But the router is not able to acquire this lease. It keeps on sending DHCP 
> REQUEST to the server. Attached logs for reference.
>
> I observed this behaviour is because the old ip lease is maintained after TIMEOUT.
> Since the old ip lease is not cleared, the DHCP REQUEST is sent back to the 
> previous DHCP Server and not the one which has assigned a new IP Address.
>
> Can You help in understanding why this behaviour is observed on TIMEOUT when the 
> dhcp server network is changed?
>
> I tested by explicitly clearing the old lease by making the s_addr = 0.0.0.0 in 
> the DHCP DISCOVER. In this case the DHCP DISCOVER and DHCP REQUEST both are 
> broadcast.
> It accepts the ip which is offered by the server.
>
> Can you please guide on how the TIMEOUT needs to be handled? Does the 
> application need to reset the interfaces and release the dhcp lease?
>
> Thank you for your help.

The key line from your logs is this:
Jul 31 13:58:25 [7450]: eth1: timed out contacting a DHCP server, using last lease

Does it work if you disable the non default option you set to use the last lease 
on timeout?

Roy