Disjoint Layer2 Configuration

In this article, we are going to pre-requisites and Procedure for configuring Disjoint Layer2 in UCS.

Pre-Requisites:

If you decided to configure, disjoint Layer2 Network in your UCS environment, Consider following:

Ethernet Switching Mode Must Be End-Host Mode

Cisco UCS only supports disjoint L2 networks when the Ethernet switching mode of the fabric interconnects is configured for end-host mode. You cannot connect to disjoint L2 networks if the Ethernet switching mode of the fabric interconnects is switch mode. 

Symmetrical Configuration Is Recommended for High Availability 

If a Cisco UCS domain is configured for high availability with two fabric interconnects, we recommend that both fabric interconnects are configured with the same set of VLANs. 

VLAN Validity Criteria Are the Same for Uplink Ethernet Ports and Port Channels 

The VLAN used for the disjoint L2 networks must be configured and assigned to an uplink Ethernet port or uplink Ethernet port channel. If the port or port channel does not include the VLAN, Cisco UCS Manager considers the VLAN invalid and does the following: 

• Displays a configuration warning in the Status Details area for the server. 

• Ignores the configuration for the port or port channel and drops all traffic for that VLAN. 

 Overlapping VLANs Are Not Supported 

Cisco UCS does not support overlapping VLANs in disjoint L2 networks. You must ensure that each VLAN only connects to one upstream disjoint L2 domain.

 

Each vNIC Can Only Communicate with One Disjoint L2 Network

 A vNIC can only communicate with one disjoint L2 network. If a server needs to communicate with multiple disjoint L2 networks, you must configure a vNIC for each of those networks.

Appliance Port Must Be Configured with the Same VLAN as Uplink Ethernet Port or Port Channel 

    For an appliance port to communicate with a disjoint L2 network, you must ensure that at least one uplink Ethernet port or port channel is in the same network and is therefore assigned to the same VLANs that are used by the appliance port. If Cisco UCS Manager cannot identify an uplink Ethernet port or port channel that includes all VLANsthat carry traffic for an appliance port, the appliance port experiences a pinning failure and goes down.

Default VLAN 1 Cannot Be Configured Explicitly on an Uplink Ethernet Port or Port Channel 

Cisco UCS Manager implicitly assigns default VLAN 1 to all uplink ports and port channels. Even if you do not configure any other VLANs, Cisco UCS uses default VLAN 1 to handle data traffic for all uplink ports and port channels

Configuration:

  Below steps explains how to configure disjoint Layer2.

Work with network team make sure cablings are done and vlans are identified and segregated.

Once you identified ports as uplink, go to Fabric Interconnect and configure ports as uplink ports.

Now you need to create vlans, portchannel and vlan groups.

In our case we are going to separate prod and backup traffic. Below is example configuration:

1. my prod vlans are 100-500 and backup vlans are 600-1000
2. Two port channel 1 and 2 for prod and backup respectively.
3. Two vlan groups called Prod and Backup.
4. Eth 1/1 and 1/2 for prod traffic, Eth1/3 and 1/4 for backup traffic.

Now lets see how to accomplish disjoint Layer2 configuration.

Configuring uplinks:

• under Equipment tab-> Fabric Interconnect A- > port 1 - > Configure port as uplink.
• Repeat the same step for all ports in both FI-A and FI-B.

Now you have uplinks ready. Lets create port channel.

Creating Port-Channel:

1. Move to LAN tab -> LAN Cloud -> Fabric A - > Port Channels.
2. Right click and select Create Port Channel. 
3. Enter 1 for ID and Prod as name and say next. 
4. Select eth1/1 and eth1/2 from list and add to port-channel.
5. Repeat the same step for Fabric-B.
6. Move to LAN tab -> LAN Cloud -> Fabric A - > Port Channels.
7. Right click and select Create Port Channel. 
8. Enter 2 for ID and Backup as name and say next. 
9. Select eth1/3 and eth1/4 from list and add to port-channel.
10. Repeat the same step for Fabric-B.

Now you can see two port channel and two uplinks associated with them.

Creating Vlans:

1. Move to LAN tab -> LAN Cloud -> VLANs
2. Right click and select Create VLANs.
3. Enter your vlan name, in my case Prod-100.
4. Make sure Common/Global option is selected.
5. Enter vlan id, in this case 100 and say ok.
6. Repeat the same step for create additional vlans. (here vlan 200-1000)

Now under Vlans we can see Vlans like Prod-100(100).., Repnet-600(600).

Creating Vlan Groups:

1. Move to LAN tab -> LAN Cloud -> VLAN Groups
2. Right click and select Create VLAN Group.
3. Enter name as Prod and select all prod vlans (100-500); click next.
4. Do not change anything in uplink ports window and click next.
5. Select Port Channel 1 for both Fabric A and B and finish.
6. Repeat the same step for creating Backup Group, this time select backup vlans and backup port channel.