PICOS version 4.0 and higher offer both Symmetric and Asymmetric routing for BGP EVPN hosts. In this document we will examine the case of Asymmetric EVPN routing with two hosts in different VNIs on two devices, R1 and R2. Figure 1 depicts how packet exchange between two hosts occurs in asymmetric BGP EVPN routing model. In the asymmetric routing model, the two end hosts, Host1 and Host2 are in two different VLANs and different VNIs. Host1 intends to communicate with Host2, sends a packet with destination MAC address of of R1 because R1 is configured as the gateway on Host1. On R1, the gateway is configured on an interface that belongs to VNI Y. The packet from Host1 on ingress at R1 is first routed to VNI Y within R1 and then bridged to R2 over the VXLAN tunnel VNI Y. On receiving the packet, R2 will strip off the VXLAN header and forward the packet to Host2.
Figure 1. EVPN Asymmetric Routing Model
The one limitation in this model is that both the devices must have the two VXLAN VNIs configured regardless if there are any hosts connected to it. In Figure 1, Host1 belongs to VNI X but both VNI X and VNI Y are configured on R1. Similarly, Host2 belongs to VNI Y but both VNI X and VNI Y are configured on R2 for asymmetric routing to work properly.
Router Configuration
R1 Configuration
Step 1: Configure VLAN ID, L3 VLAN interfaces loopback interfaces and IP addressing.
admin@R1# set evpn vrf vrf1 vni 100 prefix-routes-only admin@R1# set interface gigabit-ethernet te-1/1/1 family ethernet-switching native-vlan-id 4094 admin@R1# set interface gigabit-ethernet te-1/1/2 family ethernet-switching native-vlan-id 10 admin@R1# set interface gigabit-ethernet te-1/1/10 family ethernet-switching native-vlan-id 10 admin@R1# set l3-interface loopback lo address 1.1.1.1 prefix-length 32 admin@R1# set l3-interface loopback vrf1 address 201.201.201.201 prefix-length 32 admin@R1# set l3-interface vlan-interface vlan4094 mtu 1450 admin@R1# set l3-interface vlan-interface vlan4094 address 40.94.0.2 prefix-length 24 admin@R1# set l3-interface vlan-interface vlan10 vrf "vrf1" admin@R1# set l3-interface vlan-interface vlan10 mtu 1450 admin@R1# set l3-interface vlan-interface vlan10 address 10.1.1.201 prefix-length 24 admin@R1# set l3-interface vlan-interface vlan1111 vrf "vrf1" admin@R1# set l3-interface vlan-interface vlan1111 router-mac 00:16:16:16:16:16 admin@R1# set l3-interface vlan-interface vlan1111 mtu 1450 admin@R1# set vlans vlan-id 10 l3-interface "vlan10" admin@R1# set vlans vlan-id 30 l3-interface "vlan30" admin@R1# set vlans vlan-id 1111 l3-interface "vlan1111" admin@R1# set vlans vlan-id 4094 l3-interface "vlan4094" admin@R1# set vxlans source-interface lo address 1.1.1.1 admin@R1# set vxlans vni 100 vlan 1111 admin@R1# set vxlans vni 10 vlan 10 admin@R1# set vxlans vni 30 vlan 30
Step 2: Configure VXLAN VNI and map VNI IDs to VLAN IDs.
admin@R1# set vxlans source-interface lo address 1.1.1.1 admin@R1# set vxlans vni 100 vlan 1111 admin@R1# set vxlans vni 10 vlan 10 admin@R1# set vxlans vni 30 vlan 30
Step 3: Enable IP routing and configure VRF and hostname.
admin@R1# set ip routing enable true admin@R1# set ip vrf vrf1
Step 4: Configure BGP and OSPF related configuration
admin@R1# set protocols bgp local-as 65001 admin@R1# set protocols bgp router-id 1.1.1.1 admin@R1# set protocols bgp neighbor 2.2.2.2 remote-as "internal" admin@R1# set protocols bgp neighbor 2.2.2.2 update-source "1.1.1.1" admin@R1# set protocols bgp ipv4-unicast admin@R1# set protocols bgp evpn advertise-all-vni admin@R1# set protocols bgp evpn advertise ipv4-unicast admin@R1# set protocols bgp evpn neighbor 2.2.2.2 activate admin@R1# set protocols bgp vrf vrf1 local-as 65001 admin@R1# set protocols bgp vrf vrf1 router-id 1.1.1.1 admin@R1# set protocols bgp vrf vrf1 evpn advertise ipv4-unicast admin@R1# set protocols bgp vrf vrf1 ipv4-unicast network 10.1.1.0/24 admin@R1# set protocols ospf router-id 1.1.1.1 admin@R1# set protocols ospf network 40.94.0.0/24 area 0.0.0.0 admin@R1# set protocols ospf network 1.1.1.1/32 area 0.0.0.0
Verify Configuration
On R1 run the command run show route vrf vrf1 to display the routes. Notice below that there is a route to subnet 30.1.1.0/24.
admin@R1# run show route vrf vrf1
show ip route vrf vrf1
=======================
Codes: K - kernel route, C - connected, S - static, R - RIP,
O - OSPF, I - IS-IS, B - BGP, E - EIGRP, N - NHRP,
T - Table, v - VNC, V - VNC-Direct, A - Babel, D - SHARP,
F - PBR, f - OpenFabric,
> - selected route, * - FIB route, q - queued route, r - rejected route
VRF vrf1:
K>* 0.0.0.0/0 [255/8192] unreachable (ICMP unreachable), 04:07:17
C>* 10.1.1.0/24 is directly connected, vlan10, 04:06:28
B>* 11.11.11.147/32 [200/0] via 2.2.2.2, vlan1111 onlink, weight 1, 04:05:30
C>* 30.1.1.0/24 is directly connected, vlan30, 04:06:28
C>* 201.201.201.201/32 is directly connected, vrf1, 04:07:17
show ipv6 route vrf vrf1
=========================
Codes: K - kernel route, C - connected, S - static, R - RIPng,
O - OSPFv3, I - IS-IS, B - BGP, N - NHRP, T - Table,
v - VNC, V - VNC-Direct, A - Babel, D - SHARP, F - PBR,
f - OpenFabric,
> - selected route, * - FIB route, q - queued route, r - rejected route
VRF vrf1:
C * fe80::/64 is directly connected, vlan1111, 04:06:27
C * fe80::/64 is directly connected, vlan30, 04:06:28
C>* fe80::/64 is directly connected, vlan10, 04:06:28