I have a Cisco Cat 9500-24Q acting as Core Switch running the latest version 16.8.1a.
Under its SVIs interfaces, the command "ip helper-address x.x.x.x" pointing to an external DHCP server.
Users are being delayed to acquire a DHCP address from the external DHCP server (around 10-15 minutes).
Note that Users withing the same VLAN of the DHCP server are normally acquiring IP address.
Any idea on the above.
It will be so helpful to share the wireshark capture from the user side to check the DHCP messags between the server and the clients!
A quick tip to troubleshoot, is to change the DHCP server and use another one just for testing, it can be virtual machine for example! to see whether the same problem exists or not, if yes, it means that it's a problem of the network while if it's not, it means that the problem of the server itself!
Also, i would like to know, do you have any ACL applied on this vlan or not?
Sometimes, ACLs are affecting the performance of getting IPs from the DHCP servers!
Please, don't forget to rate all helpful responses and mark solutions!
The original post described the problem as very slow response in obtaining address assignment from DHCP server. It seems your problem is different and is that you do not receive any address at all. I suggest these steps to troubleshoot your issue:
1) post the configuration of the port where a user is experiencing this issue.
2) post the configuration of the vlan interface for the vlan where this user is located.
3) can you ping the address of the DHCP server specifying the source address for the ping as the address of the vlan interface.
4) can you verify that the DHCP server has a scope that is correctly configured for the subnet of that vlan interface.
5) are there any messages in the logs of the DHCP server indicating that it has received any requests from the subnet of that vlan interface.