This example describes a leaf-spine environment using OSPF with S5248F-ON at the leaf layer and Z9264F-ON switches used at the spine layer. While the S5248F-ON configuration is shown in this section the configuration provides OSPF configuration examples to build the Layer 3 leaf-spine topology shown in Figure 13.

Figure 13.    Example 1—Layer 3 leaf-spine topology

In Rack 1, VLAN 50 is used and devices in VLAN 50 are assigned IP addresses on the 172.16.1.0/24 network. Server 1 may specify the virtual IP address (VIP) assigned to VLAN 50 on both leaf switches, 172.16.1.254, because VRRP with VLT is configured on S528F-Leaf 1 and S5248F-Leaf 2.

Traffic is load balanced across both leaf switches. Rack 2 is configured the same as Rack 1, except VLAN 60 is used and the devices in VLAN 60 are assigned to IP addresses on the 10.60.1.0/24 network. Server 2 may specify the VLAN 60 VIP address configured on the leaf switches 10.60.1.254, as its default gateway.                                                  

The configuration commands for S5248F-Leaf 3 and S5248F-Leaf 4 are similar.

Note: On S5248F-ON switches running OS10, Telnet is disabled and SSH is enabled by default. The S5248F-ON has default credentials of admin/admin. The switch is accessible using SSH with those credentials. Changing the admin password to something more complex is recommended.                                              

1. Set the hostname, configure the OOB management interface, maintain the default gateway.
2. enable RSTP. S5248F-Leaf 1 is configured as the primary RSTP root bridge using the spanning-tree priority 0 setting. S5248F-Leaf 2 is configured as the secondary RSTP root bridge using the spanning-tree priority 4096 command.

3. Configure the VLT interconnect between S5248F-Leaf 1 and S5248F-Leaf 2. Remove each interface from Layer 2 mode with the no switchport command for interfaces eth 1/1/47- 1/1/48.
4. enter the VLT domain and add the backup destination.
5. Add the interfaces participating in VLTi. Finally, enable VLT peer routing.

6. Create a server-facing VLAN interface. Use the same VLAN ID on both leaf switches.
7. Assign an IP address to the VLAN interface. The address must be unique but on the same network on both leaf switches.
8. Configure VRRP to use VRRP version 3. Create a VRRP group and specify the group’s virtual IP address.

Note: In this example, the NIC for Server 1 is configured as an LACP NIC team. The IP address is 172.16.1.7/24. The VRRP VIP address, 172.16.1.254, is specified as the default gateway for Server 1.

9. Configure each downstream server-facing interface with an LACP port channel.
10. Configure each port channel for VLT. Port channel 10 connects downstream to Server 1 and is configured as an RSTP edge port.

11. The two upstream Layer 3 interfaces connected to the spine switches are configured.
12. Assign IP addresses as shown in Table 2.
13. Configure a loopback interface to be used as the router ID. This can be used with BGP or OSPF.

Note: If multiple loopback interfaces exist on a system, the interface with the highest numbered IP address is used as the router ID. This configuration only uses one loopback interface.

14. Configure a route map and IP prefix-list to redistribute all loopback addresses and leaf networks using OSPF. The command “seq 10 permit 10.0.0.0/8 ge 24” includes all addresses in the 10.0.0.0/8 address range with a mask greater than or equal to 24. This includes all loopback addresses used as router IDs and the 10.60.1.0/24 network used on leaf switches 3 and 4.
15. The command sequence 20 permit 172.16.0.0/16 ge 24 includes the 172.16.1.0/24 used on leaf switches 1 and 2.

16. Configure UFD. This shuts the downstream interfaces if all uplinks fail. The hosts attached to the switches use the remaining LACP LAG member to continue sending traffic across the fabric.

17. Enable OSPF globally and redistribute connected networks according to the previously defined route map. Exit configuration mode and save the configuration.

To configure BFD for OSPF:

18. Enable BFD Globally.
19. Configure OSPF on the interconnecting routers. For more information, see Open Shortest Path First (OSPFv2 and OSPFv3).
20. Establish BFD sessions with OSPFv2 neighbors:

21. BFD sessions can be established on all OSPF neighbors at the same time. Alternatively, you can also establish BFD sessions with OSPF neighbors corresponding to a single OSPF interface.
22. Exit configuration mode and save the configuration.

Note: On S5248F-ON switches running OS10, Telnet is disabled and SSH is enabled by default. The S5248F-ON has default credentials of admin/admin. The switch is accessible by default using SSH with those credentials. Changing the admin password to something more complex is recommended.

To configure Z9264F-ON spine switch:

1. Set the hostname and configure the OOB management interface and default gateway.

2. Configure the four point-to-point interfaces connected to leaf switches.
3. Assign IP addresses per Table 2.
4. Configure a loopback interface to be used as the router ID.
5. Enable OSPF on the interfaces with process 1 area 0.

Note: If multiple loopback interfaces exist on a system, the interface with the highest numbered IP address is used as the router ID. This configuration only uses one loopback interface

Configure a route map and IP prefix-list to redistribute all loopback addresses and leaf networks via BGP or OSPF.

6. The command seq 10 permit 10.0.0.0/8 ge 24 includes all addresses in the 10.0.0.0/8 address range with a mask greater than or equal to 24. This includes all loopback addresses used as router IDs and the 10.60.1.0/24 network used on leaf switches 3 and 4.
7. The command seq 20 permit 172.16.0.0/16 ge 24 includes the 172.16.1.0/24 network used on leaf switches 1 and 2.

8. Enable OSPF globally and redistribute connected networks according to the previously defined route map. Finally, exit configuration mode and save the configuration.

To configure BFD for OSPF:

9. Enable BFD Globally.
10. Configure OSPF on the interconnecting routers. For more information, see Open Shortest Path First (OSPFv2 and OSPFv3).
11. Establish BFD sessions with OSPFv2 neighbors.
12. Exit configuration mode and save the configuration.