How do we calculate HBA

Glenn Satchell Glenn.Satchell at
Wed May 28 12:30:38 UTC 2008

>Date: Wed, 28 May 2008 05:51:39 -0600
>From: "S Kalyanasundaram" <skalyanasundaram at>
>  How do we calculate HBA, I did a bit of reading in rfc 3074.  Looks like each 
octet is considered to be value 8. 
>If octets like aa:12:ae:33.. will be a valid one? How this will be calculated?
>  -Kalyan

If you're doing failover, then setting HBA is an alternative to the
'split' comand. Esentially the two commands do the same thing: they
specify what share of initial client requests should be served by each
of the servers.

In the dhcpd.conf man page the recommended setting is 'split 128;'
which gives each of the serves 50% of the addresses. There doesn't seem
to be alot of point in using settings of hba that are not 'ff' or '00'.
This setting is only for responding to initial boots. The failover
protocol balances out spare leases between the two servers anyway.

Fiddling with this setting isprobably not going to make a big
difference to the peformance of the servers. I think the vast majority
of sites just use the recomended setting of 'split 128;'.


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