The value of tmnxDhcpSvrSubnetRenewTimer specifies the renew-timer (T1).
The time at which the client contacts the server from which the addresses
in the IA_NA or IA_PD were obtained to extend the lifetimes of the
addresses or prefixes assigned to the client.
The value of this object is only meaningful when the value of
tmnxDhcpSvrSubnetAddrType is set to 'ipv6(2)'.