Technical explanation
Cilium tunnel mode supports VXLAN and Geneve encapsulation. In this routing model, Cilium nodes form an overlay mesh, and traffic exchanged between nodes is carried inside UDP-encapsulated packets. VXLAN is the default tunnel protocol and normally uses UDP port 8472. Geneve is the alternative and normally uses UDP port 6081. Operators select the protocol through the tunnel-protocol configuration setting, whose documented values are vxlan and geneve .
Encapsulation reduces the requirements placed on the underlying network. The underlay only needs to provide IP connectivity between the Kubernetes nodes and permit the selected UDP tunnel port. It does not need to learn or route individual PodCIDRs. Cilium also uses the tunnel metadata to carry information such as the source security identity, avoiding an additional identity lookup on the receiving node.
MPLS, OTV, STT, and EVPN are not supported values for Cilium’s tunnel-protocol setting. EVPN may be used in broader data-center network designs, and MPLS is a carrier-routing technology, but neither is a Cilium overlay encapsulation choice. Therefore, B is the only supported pair.
Official references
Cilium Routing ; System Requirements .
Study Guide topic: Architecture.
