DHCP failover - lease time it's always MCLT

[Gero Palacio]

Hi There,

I'm running a pair of DHCP servers in failover mode and the server that responds the DHCPREQUEST message *always* replies back with a lease time of MCLT. As I understand the protocol (DHCP Failover Protocol Draft IEFT) this should not be the case as both servers are in *normal* state. I've checked that in the dhcpd.leases file and using OMSHELL.

MTCL is currently set to 5 seconds to troubleshoot the problem. Any idea what could be wrong? Is there any condition I'm missing where the lease time is set exclusively to MTCL?

Thanks,
Gero.

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[Chris Buxton]

On Jun 29, 2015, at 12:16 PM, Gero Palacio <[hidden email]> wrote:

Hi There,

I'm running a pair of DHCP servers in failover mode and the server that responds the DHCPREQUEST message *always* replies back with a lease time of MCLT. As I understand the protocol (DHCP Failover Protocol Draft IEFT) this should not be the case as both servers are in *normal* state. I've checked that in the dhcpd.leases file and using OMSHELL.

MTCL is currently set to 5 seconds to troubleshoot the problem. Any idea what could be wrong? Is there any condition I'm missing where the lease time is set exclusively to MTCL?

Gero,

Are you saying the initial lease is set to MCLT, or that the lease is renewed at that duration as well?

The initial lease duration will always be MCLT. Always. But after the first renewal, it should be set according to the default, min, and max values.

Chris Buxton

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[Gero Palacio]

Hi Chris,

The initial lease time and all subsequent leases are set to MCLT.

On Mon, Jun 29, 2015 at 4:24 PM, Chris Buxton <[hidden email]> wrote:

On Jun 29, 2015, at 12:16 PM, Gero Palacio <[hidden email]> wrote:

Hi There,

I'm running a pair of DHCP servers in failover mode and the server that responds the DHCPREQUEST message *always* replies back with a lease time of MCLT. As I understand the protocol (DHCP Failover Protocol Draft IEFT) this should not be the case as both servers are in *normal* state. I've checked that in the dhcpd.leases file and using OMSHELL.

MTCL is currently set to 5 seconds to troubleshoot the problem. Any idea what could be wrong? Is there any condition I'm missing where the lease time is set exclusively to MTCL?

Gero,

Are you saying the initial lease is set to MCLT, or that the lease is renewed at that duration as well?

The initial lease duration will always be MCLT. Always. But after the first renewal, it should be set according to the default, min, and max values.

Chris Buxton

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[John Wobus]

My understanding is the beginning of a lease is restricted to the MCLT
to give the two servers time to synch their lease info.

Have you verified that synching is happening?  If it were my problem,
to be sure, I'd check the logs and the leases files and find leases
that both servers could only know about if they're synching  
successfully.
Both being in NORMAL state tells you synching is happening, but
it's something that can be easily checked.

I'd also verify that renewals look normal, i.e., with a unicast
request and ack and at the expected time.  (Not that I know if
the server acts differently when clients fall back to broadcasts
and/or discovers.)

There are other details to verify: that you know what
the client is requesting and what the server is configured to allow
as the maximum lease for the IP address in question.

John Wobus
Cornell University IT
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