Can't Get Dynamic Address from one pool when device is configured as Fixed Address on other, separate pool.

[matt.fura at bt.com]

Greetings.

Running into an odd issue with a clients' DHCP installation.

Customer is running DHCP 4.1.ESV-R6.  Customer was running a DHCP failover setup.  I thought this may have been the problem, so I removed the failover config and made the system a standalone, but the issue is still there.

Here's the problem:

Customer has two pools configured on the DHCP server.

130.x.x.x /20 which contains multiple Fixed Address entries for each device.  Here is fixed address example for the device in question:

                host hostname.example.com-40618610FAA1-130-x-x-91 {
                                hardware ethernet 40:61:86:10:FA:A1;
                                fixed-address 130.x.x.91;

There is also a small, 137.x.x.x/24 subnet that contains a dynamic pool for these same client to connect to when they move to another area of the building via a different GW.

The problem is, that, no matter what happens,  when a device is configured for a 'Fixed Address' in the /20 pool, if that same client tries to get a dynamic address from the smaller /24 (even if the client released the Fixed Address lease and it comes in via the proper GW) the DHCP server will not hand out an address and throws the following in the logging:

                Nov 17 18:12:17 DHCPSERVER dhcpd: DHCPDISCOVER from 40:61:86:10:fa:a1 via 137.x.x.1: network 137.x.x.x/24: no free leases

As soon as I remove the Fixed Address Entry from the /20 pool and load the configuration on the server, the device with then IMMEDIATELY get an address from the /24 without issue.

                Nov 17 18:18:43 DHCPSERVER dhcpd: DHCPDISCOVER from 40:61:86:10:fa:a1 via 137.x.x.1
                Nov 17 18:18:45 DHCPSERVER dhcpd: DHCPOFFER on 137.x.x.34 to 40:61:86:10:fa:a1 (HOSTNAME) via 137.x.x.1
                Nov 17 18:18:45 DHCPSERVER dhcpd: DHCPREQUEST for 137.x.x.34 (10.160.8.132) from 40:61:86:10:fa:a1 (HOSTNAME) via 137.x.x.1
                Nov 17 18:18:45 DHCPSERVER dhcpd: DHCPACK on 137.x.x.34 to 40:61:86:10:fa:a1 (HOSTNAME) via 137.x.x.1

After the device has an address, the client will then release:

               Nov 17 18:30:00 DHCPSERVER dhcpd: DHCPRELEASE of 137.x.x.34 from 40:61:86:10:fa:a1 (HOSTNAME) via eth0 (found)

I will add the above listed fixed entry back into the /20 pool, load the config, and again, the client will not get an address from the /24:

                Nov 17 18:30:03 DHCPSERVER dhcpd: DHCPDISCOVER from 40:61:86:10:fa:a1 via 137.x.x.1: network 137.x.x.x/24: no free leases
                Nov 17 18:30:07 DHCPSERVER dhcpd: DHCPDISCOVER from 40:61:86:10:fa:a1 via 137.x.x.1: network 137.x.x.x/24: no free leases

I can't for the life of me figure why this is happening.   A client having a fixed address in one pool should have no effect on getting an address from another pool if it comes in via the proper GW, no?  Please let me know if any other info is needed.  I'll be glad to provide this.

Regards,

Matthew Fura | Sr. TAC Engineer | BT Diamond IP | Office +1.610.280.2339 | Fax +1.610.423.4774 | http://bt.diamondip.com<http://bt.diamondip.com/>

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