Knowledge Base ISC Main Website Ask a Question/Contact ISC
Quick Jump Menu
Categories
There are no subcategories in this category.
1 What is DHCP Failover?

DHCP Failover is a mechanism whereby two DHCP servers are both configured to manage the same pool of addresses so that they can share the load of assigning leases for that pool, and provide back-up for each other in case of network outages. Failover partnerships…

2 Securing dhcpd against unauthorised OMAPI control connections

ISC DHCP has support for OMAPI, the Object Mapping Application Protocol Interface. OMAPI is an API that can be used for limited control over ISC DHCP server operations. ISC DHCP also includes omshell, a utility which will communicate with the server (if the…

3 Avoiding infinite loops (that can cause dhcpd to segfault or crash)

"With great power comes great responsibility"Infinite Loops The configuration language used for ISC DHCP is quite complex and provides the administrator with a great deal of power to affect the processing of the server and, to a lesser degree, the client.…

4 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…

5 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…

6 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…

7 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/dhcpd.pid` /usr/local/sbin/dhcpd If you have…

8 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).