Failure of dhcp server failover

Niall O'Reilly niall.oreilly at ucd.ie
Sun May 1 18:13:20 UTC 2016



On 1 May 2016 09:24:00 BST, Eugene Grosbein <eugen at grosbein.net> wrote:
>
>As I have wrote in the first letter, AP makes use of several IP
>addresses (one per vlan)
>asking for them using the same MAC address. Such requests differ in
>option 82 only,
>so I'm forced to use classes and matching against agent.circuit-id.
>
>Is it possible to assign more than one fixed-address to the same MAC
>depending on vlan tag
>without usage of classes?

I think so, but details of your network topology may give problems.
If the tuple (Mac address, relay IP address) is unique and trustworthy for each IP address you need to assign, there is a simple solution without needing failover or classes. In this case, you'll need either

(a) multiple fixed-address values in the host { } declaration, or

(b) multiple host { } declarations, each with the same MAC address, but with its own distinct name and IP address.

The DHCP relay will insert its own IP address as gwaddr to identify the originating (v)LAN, and each DHCP server will select a host declaration with matching fixed-address. ISC DHCP server can't do anything useful with dot1q tags.

With either of these approached, you must duplicate the host declaration on the different DHCP servers. With multiple host declarations, each needs a unique name, which needn't match anything in the DNS.

IHTH
Niall O'Reilly

-- 
Sent from Kaiten Mail. Please excuse my brevity.


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