Load balancing issue on busy /23 networks (v4.2.5)
Nicolas C.
dhcp at nryc.fr
Mon Mar 18 13:53:57 UTC 2013
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?
* 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.
* Issue with our switches and some DHCP-related security settings?
* All of the above?
I tried to increase the "load balance max seconds" value to 10 seconds
with no success. I have seen lots of messages about the "peer holds all
free leases" but very few diagnostics and solutions.
Regards,
Nicolas
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