DHCP subnet allocation issue

[aklausner]

Hello,

We have configured a local dhcp server on our routers. The issue is that the people onsite are experiencing connections problems, after looking into the issue, we found out that sometime the dhcp server allocates a wrong subnet mask to the client. The router delivers a /8 subnet mask instead of /24. Has anyone experienced this issue before ?

Here is the config of the dhcp server on our router :

ip dhcp excluded-address 45.1.0.1 45.1.0.10

ip dhcp ping packets 3

!

ip dhcp pool lan-pool

network 45.1.0.0 255.255.255.0

domain-name test.int

dns-server 1.1.1.1 1.1.1.2

default-router 45.1.0.1

!

The network in here is a class A so it might related, even though the subnet mask indicates a /24. I'm not sure if we have to force further the mask with the subnet prefix-lenght 24

[lgijssel]

Never had this issue before, it should not occur under normal circumstances.

Two tips:

1: Although not 100% applicable, please verify that your config includes the command: ip subnet zero.

2: Verify that your IOS is recent and not ED, T or whatsoever. If possible load a GD image.

Regards,

Leo

[tekha]

Confirm that it is actually the router that is assingning the ip address and wrong netmask, may be that there is another DHCP server ouy there, not called 45.1.0.1.

This has tricked me on more then one occasion, with DHCP problems.

[aklausner]

Well, to quickly reply to Leo, we're running a 12.3-8T4 k9, and ip subnet zero is set. As for your question, we dont have any other dhcp servers onsite, and the clients do indicate ( in the winipcfg ) that it is our routers that delivered these addresses ( still need to catch a debug for it though ... ).

[miclacs13]

hi,

maybe you should include: ip classless command

hth

miclacs13

[aklausner]

Hi,

Ip classless is already set...

Thanks

Alain,

[timm.benkula]

It may not be a Cisco/router problem. I've seen other instances of Windows PC's using none Microsoft DHCP servers, obtaining bad Subnet Masks. Usually doing an ipconfig/release - renew results in obtaining the correct address. I haven't ever found a workable solution though.