expired lease problem

[project722]

shared-network "temp" {
        subnet 172.210.140.0 netmask 255.255.252.0 {
                option domain-name "example.net";
                option routers 172.210.140.1;
                ## Define the DHCP pool and access list for this pool.
                pool {
                        allow unknown-clients;
                        failover peer "dhcp-failover";
                        range 172.210.140.2 172.210.140.255;
                        range 172.210.141.1 172.210.141.255;
                        range 172.210.142.1 172.210.142.255;
                        range 172.210.143.1 172.210.143.254;

                }
        }
        subnet 172.210.144.0 netmask 255.255.252.0 {
                option routers 172.210.144.1;

        }
 }

I can't post log entries as we have expanded the pool to patch the issue,
so currently there are no errors. However, this pool only shows 74%
utilization. And all it takes is a few more turn-ups to cause this problem.



      Subnet 172.210.140.0/22
--------------------------------------------------


     Monitoring:      ON
     Warning limit:   80%
     Critical limit:  90%
     Active leases:   762/1018 (74.9%)

As I've mentioned before, the only thing that stands out to me in
dhcpd.leases is the fact that we have a couple hundred of "expired" leases,
which could and should be used, even though these are actually being held
in the expectation that the previous client will return. (At least, that is
my understanding)

But, what is expected behavior here? For example, if we have 500 leases,
250 of them have a binding state of active and the other 250 have expired
if a new client comes along DHCP should free up one of the expired ones,
correct?




On Tue, Nov 14, 2017 at 3:24 PM, Bill Shirley <
bill at c3po.polymerindustries.biz> wrote:

> Post your pool definition and log file excerpts.
>
> Bill
>
>
> On 11/14/2017 12:07 PM, project722 wrote:
>
> We had an unusual problem last night where the server was not able to give
> out any more leases from a specific pool. The server logs showed " no more
> free leases". This is a RHEL 6.7 server running dhcp 4.1.1.
>
> We have scripts that run which look for active leases. In the pool in
> question we had over 200 available leases but the server was unable to
> provide them to a client. I dug around in dhcpd.leases and found what I
> think is the problem. I found a ton of leases in the "expired" state with
> an end date of 11/6. Which, If I am correct, will never move into it next
> binding state of free so it can be used because its a date in the past.
>
> Here is an example of one:
>
> lease 172.210.141.159 {
>   starts 2 2017/11/07 11:40:37;
>   ends 2 2017/11/07 12:10:37;
>   tstp 2 2017/11/14 11:55:37;
>   cltt 2 2017/11/07 11:40:37;
>   binding state expired;
>   next binding state free;
>
> Am I correct here? If so, what causes this problem and how can I fix it? I
> have restarted dhcpd, but that does not help. If I were to edit
> /var/lib/dhcp/dhcpd.leases manually and remove these entries what are some
> things I should take into consideration?
>
>
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