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1 Why does "dhclient -6" not work if I haven't already enabled IPv6 on the interface?

IPv6 makes extensive use of the "link-local" address. This address is configured automatically when the interface is brought up. Various IPv6 subprotocols, including Neighbor Discovery Protocol (NDP) and DHCPv6, require and use this address. The IPv6 link-local…

2 Formatting MAC addresses in dhcpd (or 'why does binary-to-ascii strip leading zeroes?')

This question arises from time to time when an administrator uses binary-to-ascii in dhcpd.conf, hoping to obtain the hardware address of a device that has been assigned a lease. The problem is that where a component of the address has a leading zero, this…

3 Migration Tips For Upgrading From DHCP 3 to DHCP 4

ISC is ending support for DHCP 3.1-ESV, the last supported version of the DHCP 3 family of software releases. Customers who wish to use a supported version of the software are advised to consult the DHCP versions page and select a "Current" or "Extended Support…

4 How do you have dhcpd reload its configuration file?

At this time, the dhcpd server doesn't have any reload mechanism. It doesn't handle HUP signal nor have a 'soft' reconfiguration method. The server has to be stopped and restarted, for example: kill `cat /var/run/` /usr/local/sbin/dhcpd If you have…

5 Do the list of parameters in the dhcp-parameter-request-list need to be in hex?

Yes; if you're using the concat() syntax, the additional option numbers are represented in hex. This is because of the way that dhcpd.conf is parsed. As an example 17,18 would get options 23 (default-ip-ttl) and 24 (path-mtu-aging-timeout).