Load balancing issue on busy /23 networks (v4.2.5)

[Nicolas C.]

Le 18/03/2013 14:53, Nicolas C. a écrit :
> Hello,
>
> I have two DHCP servers (v.4.2.5) in failover mode and on some networks
> I have issue with load-balancing :
>
> Mar 18 13:40:28 primary dhcpd: balancing pool b8e1ea38 172.20.24.0/23
> total 505  free 128  backup 190  lts -31  max-own (+/-)32
> Mar 18 13:40:28 primary dhcpd: balanced pool b8e1ea38 172.20.24.0/23
> total 505  free 127  backup 191  lts -32  max-misbal 48
>
> Mar 18 13:40:28 secondary dhcpd: balancing pool b9238a10 172.20.24.0/23
>   total 505  free 302  backup 17  lts -142  max-own (+/-)32  (requesting
> peer rebalance!)
> Mar 18 13:40:28 secondary dhcpd: balanced pool b9238a10 172.20.24.0/23
> total 505  free 302  backup 17  lts -142  max-misbal 48
>
> On busy hours, on the secondary, the "backup" reaches "0" and the server
> makes "peer holds all free leases" errors.
>
> On others (less busy) networks, everything works fine :
>
> Mar 18 14:30:07 secondary dhcpd: balancing pool b91847d8 172.21.4.0/23
> total 505  free 142  backup 214  lts 36  max-own (+/-)36
> Mar 18 14:30:07 secondary dhcpd: balanced pool b91847d8 172.21.4.0/23
> total 505  free 145  backup 211  lts 33  max-misbal 53
>
> Mar 18 14:30:07 primary dhcpd: balancing pool b8d6a800 172.21.4.0/23
> total 505  free 145  backup 211  lts -33  max-own (+/-)36
> Mar 18 14:30:07 primary dhcpd: balanced pool b8d6a800 172.21.4.0/23
> total 505  free 142  backup 214  lts -36  max-misbal 53
>
> This is the failover configuration on the primary :
>
> failover peer "pmf_pth" {
>          primary;
>          address 172.20.0.2;
>          port 647;
>          peer address 172.24.0.2;
>          peer port 647;
>          max-response-delay 30;
>          max-unacked-updates 10;
>          load balance max seconds 10;
>          mclt 1800;
>      split 128;
>      auto-partner-down 900;
> }
>
> What could be the cause of the unbalance?
>
>    * Corruption of the leases database? If yes, should I stop the
> secondary and delete the "dhcpd.leases" file to rebuild it?

I did it and now everything works but maybe it's a temporary fix?

Mar 19 16:20:58 primary dhcpd: balancing pool b895aa38 172.20.24.0/23 
total 505  free 106  backup 160  lts -27  max-own (+/-)27
Mar 19 16:20:58 primary dhcpd: balanced pool b895aa38 172.20.24.0/23 
total 505  free 106  backup 160  lts -27  max-misbal 40

Mar 19 16:24:55 secondary dhcpd: balancing pool b8662aa8 172.20.24.0/23 
  total 505  free 106  backup 160  lts 27  max-own (+/-)27
Mar 19 16:24:55 secondary dhcpd: balanced pool b8662aa8 172.20.24.0/23 
total 505  free 106  backup 160  lts 27  max-misbal 40


>    * Clients not willing to switch DHCP server, forcing on server to
> have to many leases? Our Windows clients have Symantec Endpoint
> Protection 12 with the "Smart DHCP" activated.

I put a "deny booting" one DHCP server and a client running SEP has no 
problem switching to the other when its lease expires.