* the entry "option subnet" takes the
subnet mask not the subnet address,
while the busybox dhcp-client was
fine with it, the isc-dhcp-client complained with
Error: an inet prefix is expected rather than "10.23.24.113/10.23.24.0".
If we don't provide a DNS server via DHCP to the BTSs, then their
ntpdate will not succeed in contacting pool.ntp.org (resolver failure),
which in turn means they have the wrong date, which again in turn leads
to failing opkg update or openvpn certificate verification failures.