A 88x router is connected to a CMTS modem and gets an IP adres through DHCP.
From time to time a DHCP lease renewal fails at T1 or T2 (or sometimes both).
The reason for failure is probably the ISP DHCP server but is not important for this story.
The Cisco DHCP client only tries to renew the lease at T1 (unicast) and T2 (broadcast).
So after two tries the Cisco DHCP client gives up and waites for end of lease to obtain a new one.
But according to RFC 2131 the client should keep trying to renew the lease after T1 (or T2) has passed.
<quote>
In both RENEWING and REBINDING states, if the client receives no
response to its DHCPREQUEST message, the client SHOULD wait one-half
of the remaining time until T2 (in RENEWING state) and one-half of
the remaining lease time (in REBINDING state), down to a minimum of
60 seconds, before retransmitting the DHCPREQUEST message.
</quote>
Is the Cisco DHCP client not RFC compliant or is it possible to enable this behaviour with a command?
The word SHOULD implies that a vendor can ignore this part if there is a good reason to do so.
If this is the case and Cisco choose not to implement this part does anyone know why?
