As I know, VXLAN uses OSPF for its underlay. However, it seems BGP is involved in the underlay, but I cannot figure out the purpose.
A VTEP encapsulates a packet, and if OSPF is deployed, every device should be able to route the packet to another VTEP via the outer-MAC and outer-IP. What BGP actually does in the VXLAN?
Apparently you have to have BGP.
A VLAN is configured for each segment - sending segment, VRF segment and receiving segment.
BGP and EVPN configurations ensure redistribution of this information across the VXLAN setup.https://www.cisco.com/c/en/us/td/docs/switches/datacenter/pf/configuration/guide/b-pf-configuration/Introducing-Cisco-Programmable-Fabric-VXLAN-EVPN.htmlHTH
Thanks for your information. I just finished it. There are another questions:
1.) If VTEPs advertises every end host’s information while they attach, in what circumstance ARP request is needed? Will the information timeout?
2.) As I know, EVPN seems to be related to MPLS. I would like to ask how SPINEs route the packets? Do they parse the outer-IP and look up their routing table?