DHCP lease logging between peers

Nate Collins ncollins at xes-inc.com
Mon Jul 15 14:00:33 UTC 2019


Hello,

I'm looking to inquire about the logging behavior of isc-dhcp-server when running with a peer, and whether or not our environment is configured correctly to allow the DHCP transaction logs to be shared between the two.

Our network has two servers running isc-dhcpd-4.3.3 configured as failover peers (configuration below). Both of these servers are logging to /var/log/syslog, and both servers log the transactions of the other server: 

server1:

 # cat /var/log/syslog | grep -i b8:27:eb:00:11:22
Jul 15 08:51:31 server1 dhcpd[1303]: DHCPREQUEST for 10.0.7.143 from b8:27:eb:00:11:22 via bond0
Jul 15 08:51:31 server1 dhcpd[1303]: DHCPACK on 10.0.7.143 to b8:27:eb:00:11:22 via bond0

server2:

 # cat /var/log/syslog | grep -i b8:27:eb:00:11:22
Jul 15 08:51:31 server2 dhcpd[19642]: DHCPREQUEST for 10.0.7.143 from b8:27:eb:00:11:22 via bond0
Jul 15 08:51:31 server2 dhcpd[19642]: DHCPACK on 10.0.7.143 to b8:27:eb:00:11:22 via bond0

Occasionally, however, we will see it where a static DHCP lease is handed out by one server, but the lease is not logged in the syslog file of the other server, despite being in both dhcpd.leases files:

server1:

 # cat /var/log/syslog | grep -i b8:27:eb:ab:cd:ef
...
Jul 12 07:33:03 server1 dhcpd[2094]: DHCPREQUEST for 10.0.7.243 from b8:27:eb:ab:cd:ef via bond0
Jul 12 07:33:03 server1 dhcpd[2094]: DHCPACK on 10.0.7.243 to b8:27:eb:ab:cd:ef via bond0

server2:

 # cat /var/log/syslog | grep -i b8:27:eb:ab:cd:ef
 #

Note that the logs haven't been rotated. We notice this going both ways (primary -> secondary, secondary -> primary), for both static leases and for the dynamic address pool.

The failover configuration of the two servers are as follows (let me know if more is needed to debug this issue):

# server1 /etc/dhcp/dhcpd.conf:

failover peer dhcp-failover {
    primary;
    address 10.0.0.201;
    port 647;
    peer address 10.0.0.202;
    peer port 647;
    max-response-delay 60;
    max-unacked-updates 10;
    load balance max seconds 8;
    mclt 3600;
    split 128;
}

# server2 /etc/dhcp/dhcpd.conf:

failover peer dhcp-failover {
    secondary;
    address 10.0.0.202;
    port 647;
    peer address 10.0.0.201;
    peer port 647;
    max-response-delay 60;
    max-unacked-updates 10;
    load balance max seconds 8;
}

Ultimately we'd like it so that all DHCP transactions from one server is logged by the other server; is there some configuration option corresponding to this? Again, let me know if more sections from our configuration or more information about our layout is needed.

Thanks.


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