From VLAN 2700 not getting IP from DHCP Servers

[meshekar51]

Hi Everyone,

We are having Hybride DHCP servers(Infoblox) only for VLAN 2700 users we are not getting the IP address 

Note : only users who are connected from CORE - access - Users having this DHCP issue

Users who connected to Disctribution - Access- Users getting the IP from DHCP servers from same VLAN

from packet capture from core switch we are getting DHCP DISCOVER OFFER AND Negative ACK MESSAGES

i am suspecting issue in CORE switch, kindly help me here

[marce1000]

 - Are you using a correct DHCP relay setup for the particular  VLAN ?
   M.

[Georg Pauwen]

Hello,

we need to know how the core switch is connected to the DHCP server. Can you post a schematic drawing of your topology ? Also, seeing the running configuration of the core switch might render a clue...can you post that as well ?

[paul driver]

Hello

You shouldn't really require dhcp relay when the dhcp servers are local to the estate, and if you dhcp snooping active it shouldn't ever be applied to the core switch

Regards the hosts that are attached direclty to the core, are their ports in a adminstrative mode of access and have stp portfast enabled?

Can you post the config of the core.

[lucasfreitas83]

Hello,

Do you have a DHCP snooping in the Core? if you have the port connect in the DHCP is mark with trust?

I think the best way that you have interface vlan only in the Core, the distribution switches have interface vlan in this vlan?

Verify your helper address in the core, try ping DHCP with source VLAN2700 in the core, for test connectivity.

Please rate and mark posts accordingly if you have found any of the information provided useful.
It will hopefully assist others with similar issues in the future.

Best regards,
Lucas Freitas

[meshekar51]

Hi Lucas,

We have snooping enabled in core, and all the IP address are reachable.

Thanks for quick reply we have found the resolution we found rough host which was causing the problem.

Steps: captured wireshark from core uplink to one of the host which was not getting the IP then we found one of the host sending the offer to these host then we captured rough host as source and which is not getting ip as destination (SPAN) then we used to get NAK messages in capture, then we shut that ROUGH port and configured snooping for VLAN 2700

[meshekar51]

Thanks to all.....