In this part we are going to look at the multisite setup on the Core DC switches. The last part was a bit long so wanted to put this in its own part.

Lets remind ourselves of the topology:


The multisite setup is only required on the DC Core switches and is pretty light.

Global Configuration

There is some global configuration that needs to be done on the Core switches, this is different for each DC:


evpn multisite border-gateway 100
  delay-restore time 300


evpn multisite border-gateway 200
  delay-restore time 300

This is setting up multisite on the Switches and assigning each DC a Multisite Site-Id.

Interface Configuration

The interfaces on the Core switches pointing back into the Fabric and between the Core switches within each DC need to be configured for fabric tracking:

interface Ethernet1/2-4
  evpn multisite fabric-tracking

The interfaces on the Core switches that connect the two DCs need to be configured for DCI tracking:

interface Ethernet1/1
  evpn multisite dci-tracking

The switches also need an additional loopback interface which we also need to add into the NVE configuration:


These should be created as loopback100 and also put into the OSPF domain:

interface loopback100
  ip address ......./32
  ip router ospf UNDERLAY area

Then we need to reference the loopback in the nve interface:

interface nve1
  multisite border-gateway interface loopback100

The status of the loopback100 interface is confusing at this stage:

loopback100 is down (Administratively down)
admin state is up,
  Hardware: Loopback
  Internet Address is
  MTU 1500 bytes, BW 8000000 Kbit , DLY 5000 usec
  reliability 255/255, txload 1/255, rxload 1/255
  Encapsulation LOOPBACK, medium is broadcast
  Auto-mdix is turned off
    0 packets input 0 bytes
    0 multicast frames 0 compressed
    0 input errors 0 frame 0 overrun 0 fifo
    0 packets output 0 bytes 0 underruns
    0 output errors 0 collisions 0 fifo
    0 out_carrier_errors

The reason we see this is because the rest of the configuration isn't in place yet. Once it is, this interface will come UP UP.


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