01-09-2020 11:08 PM
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
01-09-2020 11:57 PM
- Are you using a correct DHCP relay setup for the particular VLAN ?
M.
01-10-2020 01:18 AM
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 ?
01-10-2020 02:00 AM - edited 01-10-2020 12:04 PM
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.
01-10-2020 09:18 AM
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
01-10-2020 07:56 PM
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
01-10-2020 07:58 PM
Thanks to all.....
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