Egress ECMP Load Distribution for VXLAN Traffic from the VTEP Switch


Equal-cost multi-path routing (ECMP) is a routing strategy where next-hop packet forwarding to a single destination can occur over multiple best paths.


Tunnel next hops are updated based on underlay routes information. RIB/FIB information is leveraged to program next hops for a tunnel remote endpoint.


 If multiple next hops exists for a tunnel remote endpoint, an ECMP group is created using the list of next hops and the tunnel is programmed accordingly.


For example, a tunnel leaf1toleaf 2 with a remote IP address 32.4.11.1, there are 2 next hops, 192.178.0.6 and 192.178.0.2.


Traffic going over tunnel leaf1toleaf 2 is hashed over these two next hop links.


CLI (network-admin@lleaf11) > tunnel-show


scope:                           cluster

name:                            leaf1toleaf2

type:                            vxlan

vrouter-name:                    leafpst1

peer-vrouter-name:               leafpst2

local-ip:                        22.3.11.1

remote-ip:                       32.4.11.1

router-if:                       eth12.11

next-hop:                        192.178.0.6

next-hop-mac:                    66:0e:94:8c:d4:0f

nexthop-vlan:                    4091

remote-switch:                   0

active:                          yes

state:                           ok

error:                           

route-info:                      32.4.11.0/24

scope:                           

name:                            

type:                            

vrouter-name:                    

peer-vrouter-name:               

local-ip:                        

remote-ip:                       

router-if:                       

next-hop:                        192.178.0.2

next-hop-mac:                    66:0e:94:5b:90:2b

nexthop-vlan:                    

remote-switch:                   4092

active:                          0

state:                           ok

error:                           

route-info:                      32.4.11.0/24

scope:                           cluster

name:                            leaf1toleaf2-2nd

type:                            vxlan

vrouter-name:                    leafpst1

peer-vrouter-name:               leafpst2

local-ip:                        22.3.12.1

remote-ip:                       32.4.12.1

router-if:                       eth9.12

next-hop:                        192.178.0.6

next-hop-mac:                    66:0e:94:8c:d4:0f

nexthop-vlan:                    4091

remote-switch:                   0

active:                          yes

state:                           ok

error:                           

route-info:                      32.4.11.0/24

scope:                           

name:                            

type:                            

vrouter-name:                    

peer-vrouter-name:               

local-ip:                        

remote-ip:                       

router-if:                       

next-hop:                        192.178.0.2

next-hop-mac:                    66:0e:94:5b:90:2b

nexthop-vlan:                    

remote-switch:                   4092

active:                          0

state:                           ok

error:                           

route-info:                      32.4.11.0/24

 

CLI (network-admin@leaf-pst-1) > vrouter-rib-routes-show ip 32.4.11.0


vrid ip        prelen number-of-nexthops nexthop     flags      vlan intf_ip     intf_id

---- --------- ------ ------------------ ----------- ---------- ---- ----------- -------

0    32.4.11.0 24     2                  192.178.0.6 ECMP,in-hw 4091 192.178.0.5 1

0    32.4.11.0 24     2              192.178.0.2 ECMP,in-hw 4092 192.178.0.1 0

 

CLI (network-admin@leaf-pst-1) > vrouter-rib-routes-show ip 32.4.12.0

vrid ip        prelen number-of-nexthops nexthop     flags      vlan intf_ip     intf_id

---- --------- ------ ------------------ ----------- ---------- ---- ----------- -------

0    32.4.12.0 24     2                  192.178.0.6 ECMP,in-hw 4091 192.178.0.5 1

0    32.4.12.0 24     2                  192.178.0.2 ECMP,in-hw 4092 192.178.0.1 0