EVPN L3VPNv4 over SRv6 BE

The implementation of Ethernet virtual private network (EVPN) L3VPNv4 over SRv6 BE involves establishing SRv6 BE paths, advertising VPN routes, and forwarding data. Figure 1 shows how EVPN L3VPNv4 over SRv6 BE is implemented.

Figure 1 EVPN L3VPNv4 over SRv6 BE implementation

SRv6 and SRv6 VPN functions are configured on each PE, and IPv6 is enabled on the transit node.
PE2 advertises an SRv6 locator route to PE1.
Route advertisement from CE2 to PE2: CE2 advertises its IPv4 route to PE2. A static route or a dynamic routing protocol such as RIP, OSPF, IS-IS, or BGP can be configured for the communication between CE2 and PE2.
After learning the IPv4 route advertised by CE2, PE2 installs the route in its VPNv4 routing table and converts it into a type 5 EVPN route (IP prefix route).
Route advertisement from PE2 to PE1: PE2 advertises the EVPN route to its BGP EVPN peer PE1 through update messages carrying RT and SRv6 VPN SID attributes.
After PE1 receives the EVPN route, if the next hop in the EVPN route is reachable and the route matches the BGP route import policy, PE1 performs a series of actions to determine whether to install the route in the IPv4 routing table of the corresponding EVPN instance. These actions include route leaking, route recursion to an SRv6 BE path, and route selection. If PE1 installs the route, this route is then associated with an SRv6 VPN SID.
PE1 advertises the route to CE1. CE1 then learns the route from PE1 using RIP, OSPF, IS-IS, or BGP. This process is similar to that from CE2 to PE2.

Figure 2 shows route advertisement and data forwarding in an EVPN L3VPNv4 over SRv6 BE scenario.

Figure 2 Route advertisement and data forwarding in an EVPN L3VPNv4 over SRv6 BE scenario
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In the route advertisement phase:

A locator is configured on PE2.
PE2 advertises the locator route A2:1::/64 corresponding to the SID to PE1 through the IGP. PE1 then installs the route in its own IPv6 routing table.
A VPN SID (End.DT4 SID A2:1::C100) within the locator range is configured on PE2, which then generates a local SID entry.
After receiving the IPv4 route advertised by CE2, PE2 converts the route into a type 5 EVPN route (IP prefix route) and advertises it to PE1 through BGP EVPN. The EVPN route carries the SRv6 VPN SID – End.DT4 SID A2:1::C100.
After receiving the EVPN route, PE1 leaks the route to its VPNv4 routing table, converts it into a common IPv4 route, and advertises it to CE1.

In the data forwarding phase:

CE1 sends a common IPv4 packet to PE1.
After receiving the packet through the interface to which a VPN instance is bound, PE1 searches the routing table of the VPN instance for a prefix entry that matches the destination IPv4 address of the packet. After finding the associated SRv6 VPN SID and next hop, PE1 encapsulates the packet into an IPv6 packet using the SRv6 VPN SID A2:1::C100 as the destination address.
PE1 finds the route A2:1::/64 based on the longest match rule and forwards the packet to the P device over the shortest path.
Likewise, the P device finds the route A2:1::/64 based on the longest match rule and forwards the packet to PE2 over the shortest path.
PE2 searches My Local SID Table for an End.DT4 SID that matches A2:1::C100. According to the instruction specified by the SID, PE2 removes the IPv6 packet header and searches the IPv4 routing table of the VPN instance identified by the End.DT4 SID for packet forwarding.