VXLAN and BGP EVPN Configuration Guide for Dell EMC SmartFabric OS10 Release 10.5.2

DHCP relay on VTEPs

Dynamic Host Configuration Protocol (DHCP) clients in overlay communicate with a DHCP server using the DHCP relay on the VTEP switch. DHCP server and the client can reside in the same VRF or in different VRFs. If they are in different VRFs, configure the route-leaking to allow communication between the client subnet in the client-VRF and the server in the server-VRF. If they are in the same VRF, route leaking need not be configured.

DHCPv4 relay on VTEPs supports the following option 82 sub-options:

• Server ID override suboption - Sub-option 11(0xb)
• Link selection suboption- Sub-option 5(0x5)
• DHCPv4 virtual subnet selection option - Sub-option 151(0x97)
• DHCPv4 virtual subnet selection control - Sub-option 152(0x98)
• source-interface CLI for relay agents. The gateway address (giaddr) field carries the source interface address.

Use the Link selection suboption, Server ID override suboption, and source-interface to minimize the route leaking configurations. Only the DHCP server subnet needs to be leaked into client-VRF and the DHCP client-subnets in client-VRF need not be leaked into server-VRF. The source-interface must be reachable from the server-VRF, and the DHCP server sends responses to the source-interface IP.

Use the VSS suboption to send the configured client VRF information to the DHCP server to allocate an IP address based on the VRF.

Configure DHCP relay on VTEPs

OS10(config)# interface virtual-network 10
OS10(conf-if-vn-10)# ip helper-address 40.1.1.1 vrf tenant01