DHCP failover doesn't receive DHCP requests in secondary server

perl-list perl-list at network1.net
Thu Aug 16 14:33:00 UTC 2018

> On 8/15/18 6:19 PM, Philippe Maechler wrote:
> > iirc with the latest patch, only the primary server replies to clients
> > when the split value is set to 255

> When was this added?

> /Anders

This has been there for a long time.  Its just the same-ole split value.  Affects how the load balancing algorithm is applied.  From man page:

The split statement

         split bits;

         The  split  statement  specifies the split between the primary and secondary for the purposes of load balancing.  Whenever a client makes a DHCP request, the DHCP server runs a hash on the client identification, resulting in value from 0 to 255.  This is
         used as an index into a 256 bit field.  If the bit at that index is set, the primary is responsible.  If the bit at that index is not set, the secondary is responsible.  The split value determines how many of the leading bits are  set  to  one.   So,  in
         practice,  higher  split values will cause the primary to serve more clients than the secondary.  Lower split values, the converse.  Legal values are between 0 and 256 inclusive, of which the most reasonable is 128.  Note that a value of 0 makes the sec-
         ondary responsible for all clients and a value of 256 makes the primary responsible for all clients.

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