host machines are not getting IP from one DHCP but getting from second DHCP

[registrations]

my client have two DHCP servers for vlan 40 and vlan 70 configured on windows server. network setup L3 device is a Cisco router and there is a core switch stack connected with two other switch stacks. 

On the router, vlan 40 and vlan 70 are configured with their subnets and ip helper address is configured to point to windows server(where DHCP is configured). 

When my client connects a host machine(windows 10) with a switchport of vlan 40, host getting IP from vlan 40 DHCP but when same host is connected with switchport of vlan 70, it is getting same IP of vlan 40.

Similarly, we took another machine and connected it to the switchport of vlan 70, host was able to get ip from Vlan 70 DHCP  but when same connected with swithport of vlan 40, it was getting the same IP of vlan 70. 

There are no recent changes made in the network like firmware upgrade etc. 

Router and switch logs were not showing any strange thing as well 

Can someone please guide what is the core reason behind this? 

[chrihussey]

Have you tried rebooting the host machines when moving to a different VLAN to see if the results are the same?

[registrations]

Yes we have rebooted the host machines and we tested host machines of windows 10, windows 7 and mac . Unfortunately, all showing the same result 

[chrihussey]

Then maybe it is not the network and possibly the DHCP server itself. It may be retaining the MAC of the device and providing the last IP given to it regardless of subnet. Possibly a sniffer trace could shed some light on what's going on.

[paul driver]

Hello

Do you have native vlans applied for any of these vlans?

Do your broadcast vlans and dhcp server scopes have the correct subnet masks applied?

res

Paul

[Richard Burts]

I agree with Paul that we need to know more about the environment. Is inter vlan routing done on the switch or on the router? Can you give us the router config (or at least the interface config)? Also from the switch the config of the interface(s) connecting to the router. Also from the switch can you post the output of these commands

show interface trunk

show interface status

show ip interface brief

HTH

Rick

[registrations]

Rick / Paul,

we have isolated the issue to some extent. 

regarding the environment I provided the information in my posting that Cisco router is connected with ISP 

Cisco Router is connected to Core Switch Stack

Core Switch Stack is connected with two Stack A Switches(Cisco 3750 Switches) and Stack B(cisco 3750 switches )

I am sorry config files are not available 

from the config point of view,

inter vlan routing is configured on cisco router.

uplink port of core switch stack is configured as trunk and vlan 40 and 70 tagged. 

similarly uplink ports of Core switch stack to Stack A and Stack B are also configured as trunk with vlan 40 and 70 tagged 

native vlan is 1 for all these ports. 

A development we have made that this issue is only happening in Stack A and Stack B Switches. Core switch stacks are allowing switch of IPs between vlans as expected 

[Richard Burts]

Can you post the output of these commands from the stack A and stack B switches

show interface status

show interface trunk

HTH

Rick