VXLAN Part XII: Routing Exchange: intra/inter-L2VNI, EVPN-to-IP, EVPN-to-VPNv4

Edited: 25.9.2018 | Toni Pasanen

We are using BGP EVPN (MP-BGP AFI25/SAFI70-EVPN) to exchange MAC-IP (Type-2) and Prefix (Type-5) reachability information inside the VXLAN fabric between the VTEPs. Each BGP UPDATE message sent by VTEP includes L2VNI/L3VNI specific Route-Target (RT) Extended Community Path-Attribute. Based on these RTs, routes are imported to correct L2VNI/L3VNIs. Each L2VNI has VNI-specific RT, which is used for intra-VNI communication. Inside the Tenant, there is a common, Tenant specific RT used for inter-L2VNI communication.

The routing information between the external networks cannot rely only on Route-Targets. We could have an external connection over IPv4 networks by using eBGP or connection over the MPLS network by using MP-BGP (AFI1-IPv4/SAFI128-VPNv4). All of these three BGPs (BGP, BGP EVPN, and BGP VPNv4) use dissimilar address representation format in BGP updates. Let’s use the IPv4 address 192.168.100.1/24 as an example.

IPv4:    192.168.100.1/24

VPNv4: [RD]:192.168.100.1/11/112

EVPN:   [RD]:[Route-Type]:[ESI]:[MAC length]:[MAC]:[IP length]:192.168.100.1/272

Because of the different representation mode for the same address, we need to change the address format while exchanging the routing updates between BGP domains over the VXLAN Border-PE.

I am going to use the topology shown in figure 12-1 to do the deep dive to this subject.

Figure 12-1: Example Topology and IP addressing

VXLAN Part XI: Using vPC Peer Link as an Underlay Backup Path

Edited: Wednesday, 5 September 2018 | Toni Pasanen

This short post shows how VTEP Leaf switch can use a vPC peer link as a backup path to Spine switch in a situation where the Leaf switch loses connection to the Spine switch. This is recommended redundancy model when using vPC in VXLAN BGP EVPN fabric. Just like in my previous posts, I am using only one Spine switch to keep things as simple as possible.

Figure 11-1: Example Topology and IP addressing