Cisco Cayalys 9300 and Windows Sever 2019 dhcp

[jonathanghignoli]

Good morning, I have a Catalys 9300. I have a Windows Server 2019 DHCP server. Some PCs on the VLANs correctly acquire the IP from the scopes configured on the Server, some PCs on other VLANs of the 9300 are unable to acquire the IP directly from the DHCP. I attach the configuration of the 9300 and the related scopes configured on Windows Server. I will also show you which IPs cannot be assigned. Submitted the 9330 debug.

Cat 9300

interface Vlan23
description **** PC ****
ip address 10.20.100.1 255.255.252.0
ip helper-address 10.20.1.1

interface Vlan81
description *** Rete ETH TMP/TVE/TPR/CND/SALACOMPRESSORI ***
ip address 10.81.3.2 255.255.0.0
ip helper-address 10.20.1.1

interface Vlan72
description **** Rete Ethernet Legacy ****
ip address 10.71.3.1 255.255.0.0 secondary
ip address 10.72.3.1 255.255.0.0 secondary
ip address 10.71.3.251 255.255.0.0 secondary
ip address 10.72.3.200 255.255.0.0
ip helper-address 10.20.1.1

interface Vlan90
description *** BIMEC ***
ip address 10.90.3.1 255.255.0.0
ip helper-address 10.20.1.1

The scopes configured on the DHCP Server Win are
10.81.27.0/24, 10.72.27.0/24, 10.90.27.0/24, 10.20.100.0/23
Scopes 10.81.27.0 and 10.20.100.0/23 work fine.
Scopes 10.72.27.0/24 and 10.90.27.0/24 do not work.
I attach the debug.
Can you help me? Thank you

[MHM Cisco World]

Three IP secondary and one primary 

Which one is not working?

MHM

[pieterh]

NB! Scopes 10.72.27.0/24 and 10.90.27.0/24 do not work.
here you specify /24 netmask, but the switches netmask is 255.255.0.0 which means /16 netmask
maybe you need to modify the addresses as

ip address 10.71.3.1 255.255.255.0 secondary
ip address 10.71.3.251 255.255.255.0 secondary
ip address 10.72.3.1 255.255.255.0 secondary
ip address 10.72.3.200 255.255.255.0

some other remark :

ip address 10.71.3.1 255.255.0.0 secondary
ip address 10.71.3.251 255.255.0.0 secondary
=> both addresses lay within the same subnet 10.71.0.0/16 (contains 10.71.0.0 - 10.72.255.255)

ip address 10.72.3.1 255.255.0.0 secondary
ip address 10.72.3.200 255.255.0.0
=> same as above 10.72.0.0/16 

what is the reason for this? even with a /24 subnet is sounds a little strange to do so?

[jonathanghignoli]

I solved it, the problem is that if an IP is registered on the dhcp coming from vlan81 and subsequently the switch port is changed to vlan72, the dhcp does not recognize the change of vlan and the record on the dhcp remains the same because most likely the dhcp recognizes the same mac-address. So the problem is practically solved by changing the duration of the addresses in case there is a need (as in my case) to change the VLANs on the switch ports frequently. Thank you

[balaji.bandi]

you configured all point to one helper address, so check the DHCP option have right router gateway for right VLAN

make sure user port belong to same vlan to work as expected.