ISC DHCP 4.4.1 launched

ISC DHCP 4.4 is expected to be the last branch we create for ISC DHCP. The software is complete and stable, but it is difficult to extend it much further.

The release of ISC DHCP 4.4.1 is the first release on the 4.4. branch, since 4.4.0 was withdrawn. This release contains several new features as well as a number of bug fixes.

This release delivered improvements in 3 major areas:

1. Dynamic DNS additions
2. dhclient improvements
3. Support for dynamic shared libraries

Dynamic DNS Improvements:

We added three new server configuration parameters which influence DDNS conflict resolution:

1. ddns-dual-stack-mixed-mode – alters DNS conflict resolution behavior to mitigate issues with non-compliant clients in dual stack environments.

2. ddns-guard-id-must-match – relaxes the DHCID RR client id matching requirement of DNS conflict resolution.

3. ddns-other-guard-is-dynamic – alters dual-stack-mixed-mode behavior to allow unguarded DNS entries to be overwritten in certain cases

The server now honors update-static-leases parameter for static DHCPv6

dhclient Improvements:

We’ve added three command line parameters to dhclient:

1. –prefix-len-hint – directs dhclient to use the given length as the prefix length hint when requesting prefixes

2. –decline-wait-time – instructs the client to wait the given number of seconds after declining an IPv4 address before issuing a discover

3. –address-prefix-len – specifies the prefix length passed by dhclient into the client script (via the environment variable ip6_prefixlen) with each IPv6 address.  We added this parameter because we have changed the default value from 64 to 128 in order to be compliant with RFC3315bis draft (-09, page 64) and RFC5942, Section 4, point 1.

**WARNING**: The new default value of 128 may not be backwardly compatible with your environment.

If you are operating without a router, such as between VMs on a host, you may find they cannot see each other with
prefix length of 128. In such cases, you’ll need to either provide routing or use the command line parameter to set the value to 64. Alternatively you may change the default at compile time by setting DHCLIENT_DEFAULT_PREFIX_LEN in includes/site.h.

dhclient will now generate a DHCPv6 DECLINE message when the client script indicates a DAD failure

Dynamic shared library support:

Configure script,, which supports libtool is now provided with the source tar ball.  This script can be used to configure ISC DHCP to build with libtool and thus use dynamic shared libraries.

Other Highlights:

– The server now supports dhcp-cache-threshold for DHCPv6 operations
– The server now supports DHPv6 address allocation based on EUI-64 DUIDs
– Experimental support for alternate relay port in the both the server and relay for IPv4, IPv6 and 4o6 (see: draft-ietf-dhc-relay-port-10.txt)

See the complete Release notes here

Last modified: March 1, 2018 at 11:20 am