Classes and failover
Leif Arne Neset
leifa at alfanett.no
Fri Jun 27 10:56:01 UTC 2008
Rene Joergensen skrev:
> Hi there,
>
> We have a problem with dhcpd 3.1.1 running in failover.
>
> As i understand the implementation, when receiving a request, the two
> servers calculates who should reply to the request (configured via the
> "split" option).
>
> What we're seeing is that both servers reply on requests which never
> reaches the client, maybe because the relay in the Cisco/Alcatel
> equipment gets confused.
>
> But why do both of them reply?
Use Wireshark or something similar to have a look at the DHCPDISCOVER
packets. My guess is that the field "seconds elapsed" in the packets are
either 0 (zero) or larger than the value in the configuration option
"max-response-delay". If this is true both servers are supposed to
answer the discoverpackets.
Leif Arne Neset
leifa at alfanett.no
>
> We use classes to limit the number of leases:
>
> class "class3" {
> match if exists agent.circuit-id;
> spawn with option agent.circuit-id;
> lease limit 2;
> }
>
> And for circuits with fixed ip, there is a class defined:
>
> class "TN-222827" {
> match if option agent.unknown-6 = "TN-222827";
> lease limit 1;
> }
>
> And we then define a pool with the fixed IP, a pool with only one IP in
> the range, and deny them in the other pools.
>
> What we see in the logs:
>
> Jun 26 14:34:31 choke dhcpd: DHCPREQUEST for 194.19.142.187 from 00:07:e9:af:35:45 via 194.19.167.1
> Jun 26 14:34:31 choke dhcpd: DHCPACK on 194.19.142.187 to 00:07:e9:af:35:45 (eeyore) via 194.19.167.1
>
> Jun 26 14:34:31 serv01 dhcpd: DHCPREQUEST for 194.19.142.187 from 00:07:e9:af:35:45 (eeyore) via 194.19.167.1
> Jun 26 14:34:31 serv01 dhcpd: DHCPACK on 194.19.142.187 to 00:07:e9:af:35:45 (eeyore) via 194.19.167.1
>
> Normally it logs that is loadbalances, but not here.
>
> Our configuration:
>
> On the primary dhcpd:
>
> failover peer "dhcp-failover" {
> primary;
> address 194.19.194.18;
> port 647;
> peer address 194.19.194.29;
> peer port 647;
> max-response-delay 30;
> max-unacked-updates 10;
> mclt 600;
> split 128;
> load balance max seconds 3;
> }
>
> On the secondary dhcpd:
>
> failover peer "dhcp-failover" {
> secondary;
> address 194.19.194.29;
> port 647;
> peer address 194.19.194.18;
> peer port 647;
> max-response-delay 30;
> max-unacked-updates 10;
> load balance max seconds 3;
> }
>
> Any ideas why? Is it because of the classes?
>
>
>
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