LAN-VN cant get DHCP from Fusion Router

[reylite]

Hello i have an issue that my laptop on LAN-VN cant get dhcp from fusion
so the dhcp server on fusion router where it connects to border-edge then border to Edge node 
fusion to border are using overlay trunk with bgp then from border to edge using IS-IS
when i put static ip on my laptop with segmen LAN-VN i get internet access, maybe something wrong with my dhcp pool configuration
and i do put my LAN pool on DNAC

any advice ?

thank you

[Dan Rowe]

I would recommend taking embedded packet captures from edge, border, & fusion to verify the DHCP packet flow. Do you see the DHCP discover making it to the Fusion? If so, does the Fusion send a DHCP Offer back to the fabric? If the DHCP Offer is sent by the Fusion, do you see it on the Border and more importantly on the edge? 

This troubleshooting exercise should help you understand where your problem is and what you might need to do to correct it.

[reylite]

so for this case, fusion router cant act as DHCP server for LAN user, but it can for Infra-VN
so im using external DHCP server for LAN-VN

Thank you

[willwetherman]

@reylite 

The fusion router (fabric border peer device) can act as a DHCP server for both the Infa-VN and for Overlay VN IP pools. The general preference is to host DHCP on a a dedicated server that is located outside of the fabric (such as a Microsoft/Infoblox server), however using the fusion router is a convenient option for use cases such as Guest and IOT that need basic DHCP.

Example configuration

The following Guest VN IP pool is provisioned on my fabric edge switches with a DHCP relay server/IP helper of 10.1.1.1

Fabric Edge Anycast SVI

interface Vlan1025
description Configured from Cisco DNA-Center
mac-address 0000.0c9f.fb95
vrf forwarding Guest
ip address 10.100.11.1 255.255.255.0
ip helper-address 10.1.1.1
no ip redirects
ip route-cache same-interface
no lisp mobility liveness test
lisp mobility Site1-Guest-IPV4

The following configuration is applied to my fusion router. The IP address that is configured for DHCP relay (10.1.1.1) has been configured under a loopback interface that is associated to the Guest VRF and then advertised into BGP so that it is reachable from the fabric borders. A basic DHCP pool has then been configured for the Guest clients. This is in production for one site and is working without any issues.

Fusion Router

interface Loopback100
 description Guest VN DHCP Relay Loopback
 vrf forwarding Guest
 ip address 10.1.1.1 255.255.255.255
!
router bgp 65001
 address-family ipv4 vrf Guest 
 network 10.1.1.1 mask 255.255.255.255
!
ip dhcp excluded-address 10.100.11.1 10.100.11.10
!
ip dhcp pool Guest
network 10.100.11.0 255.255.255.0
default-router 10.100.11.1
dns-server 8.8.8.8

Hope that this helps

Will