Cisco NX-OS: VXLAN Multicast Control Plane

Two control planes for the VXLAN technology:

Multicast control plane (flood and learn)
MP-BGP EVPN control plane

Virtual Extensible Local Area Networks (VXLANs) allows to extend reachability of a VLAN within a data center over Layer 3.

Every VTEP with specific VXLAN and certain VNI will join the same multicast group. To learn remote MAC addresses, the VTEP will use conversational MAC address learning technique: learn only actively speaking MAC addresses.

note: Always Read Guidelines and Limitation for specific hardware
Cisco Nexus 5600 Series NX-OS Layer 2 Switching Configuration Guide, Release 7.x

Set switching mode to store-and-forwarding
IP unicast reachability between VTEPs
PIM BIDIR reachability between VTEPs
Enable features “vn-segment-vlan-based” and “nv overlay”

Store-and-forwarding

conf t
   hardware ethernet store-and-fwd-switching
copy run start
reboot

IP unicast reachability between VTEPs

EIGRP as an example. The goal is just connectivity between Loopback interfaces:

feature eigrp
!
router eigrp 100
  address-family ipv4 unicast
    autonomous-system 100
    router-id 1.1.1.1

interface Ethernet1/1
  no switchport
  ip address 172.16.12.1/30
  ip router eigrp 100
  no shutdown

interface Ethernet1/2
  no switchport
  ip address 172.16.13.1/24
  ip router eigrp 100
  no shutdown

interface loopback0
  ip address 1.1.1.1/32
  ip router eigrp 100

PIM BIDIR reachability between VTEPs

Configure PIM first, check that is working and than enable BIDIR. Configure PIM with rp-address 1.1.1.3 (NXOS3) on all Nexus devices:

conf t
feature pim

ip pim rp-address 1.1.1.3 group-list 224.0.0.0/4

interface loopback0
  ip pim sparse-mode

interface Ethernet1/1
  ip pim sparse-mode

interface Ethernet1/2
  ip pim sparse-mode

How to check multicast receiving:

On one Leaf Nexus Loopback interface configure join-group:

NXOS1:
interface loopback0
  ip igmp join-group 227.7.7.7

Check (*, 227.7.7.7 ) in the RP pim routes => receiver is ok:

How to check multicast sending:

On the second Leaf Nexus run “ping multicast 227.7.7.7 interface e1/1”

NXOS2# ping multicast 227.7.7.7 interface e1/1
PING 227.7.7.7 (227.7.7.7): 56 data bytes
64 bytes from 172.16.12.1: icmp\_seq=0 ttl=254 time=6.742 ms
64 bytes from 172.16.12.1: icmp\_seq=1 ttl=254 time=10.17 ms
64 bytes from 172.16.12.1: icmp\_seq=2 ttl=254 time=13.882 ms
64 bytes from 172.16.12.1: icmp\_seq=3 ttl=254 time=11.793 ms
64 bytes from 172.16.12.1: icmp\_seq=4 ttl=254 time=8.43 ms