Systems are unable to acquire ip address form particular pool

[rammi.malek]

Hi,
I have created 10 pools for 10 vlans(vlan 2 to vlan 11) in my dhcp server. Till yesterday everything was fine with my LAN but today i found that few systems that are configured for vlan 8 are unable to acquire ip address from that pool. When i tried configuring the systems with another vlans(vlan 2 to vlan11)   they are acquiring ip address from particular range  and able to communicate in LAN. My question is why those systems are unable to acquire ipaddress from vlan 8 pool? I have checked loggs in the dhcp server, no loggs generated and everything is fine with the server. What could be the reason? How could i solve this problem? 

regards

rammi

[Nagaraja Thanthry]

Hello,

Are you getting addresses from any other specific pool? Could it be that

there is some sort of vlan leaking (somebody physically bridged two VLANs)?

If the VLANs get bridged, the dhcp request gets broadcasted to other vlan as

well and the SVI will forward that request as its own and you might get an

IP that does not belong to VLAN 8.

Hope this helps.

Regards,

NT

[Peter Paluch]

Hello Rammi,

Is it possible that your pool for VLAN 8 has been exhausted? If you have a recent IOS you may try using the command show ip dhcp pool to see statistics about each pool and the number of leased addresses. An exhausted pool is often the cause of similar issues.

Also try using the debug ip dhcp server events command to see whether the DHCP requests sent by clients in VLAN 8 are correctly received and processed by your router. Using this debug output may provide you with additional clues to narrow down the cause of your problem.

Best regards,

Peter

[TimLaffan]

Have you checked that the ip helper-address is there for VLAN 8, also do you run ACL's