Yeah!

The topic I like to discuss today is about port-channel in Nexus. Port-channel bundles physical links to form one logical link by using the channel group that provides aggregated bandwidth and redundancy. On the M-series module, you can bundle up 8 physical links but with the release of Cisco NX-OS 5.1, you can bundle up to 16 ports on the F series module. The Port-channel feature does not need a license in order for you to use it. However, since you are going to use VDCs, you need to have the Advanced Services license. This need to be installed before you configure ports within the VDC. Make sure that all member ports are in the same VDC. You can have them configured in any desired VDC but if you are going to configure the load balancing, you must do it in the default VDC.

Though they always said that it’s not good to compare, it’s not true in the networking technology or maybe in other technologies not only in the network world. We always compare. Like in IOS, NX-OS requires all the members of port-channel to have compatible parameters. Else, the port-channel will not form.

So, the first thing that you need to do is to verify whether the following parameters are the same for all member ports:

• port mode
• speed
• MTU
• shut lan
• MEDIUM
• span mode
• load interval
• Access VLAN, Trunk native VLAN, and Allowed VLAN list
• 802.3x flow control setting

How do you do that? Use the “show port-channel compatibility-parameters” command. We will discuss more of it in my future port-channel lab post.

Another thing that is important to take note is that Cisco NX-OS does not support PAgP. The Cisco proprietary Port Aggregation Protocol (PAgP) is not supported for some reasons.

PORT-CHANNEL TOPICS:

• Default Port-Channel Parameters
• Port-Channel Basic Settings
• Configuring Port-Channel
• Port-Channel Load Balancing
• Port Channel Verification

Firstly, let’s discuss VTP version 3. Do you recall what is VTP version 3? Ok, this is the 3rd version of VTP. So what’s the difference with this new version compare to old versions? VTP version 1 and 2 only support a normal range of VLANs from 1 – 1005 but VTP version 3 expands the VLAN range up to 4094. Yes, it is supporting the entire VLAN range! It also supports enhanced authentication where you can configure the password as hidden or secret. VTP version 3 also supports MST and transfer information of private VLANs. Not only that, there is primary server and secondary server concept here where the primary server is responsible for updating and sending updates to VLANs while secondary server serves as a backup. Interesting right? However, in Cisco NX-OS there is no VTP version 3. Yeah, after giving you a lot of exciting features, you cannot use it in Nexus.

There is, however, another limitation. IOS VTP pruning is only good for normal VLAN range but in Nexus 5K (Nx5K), it does not support VTP pruning at all.

In NX-OS, the default mode is disabled. Like the routing protocols that need to be enabled manually, you also need to manually enable VTP using the “feature vtp” command. Moreover, NX-OS supports VTP mode off. Off mode behaves like transparent mode but it does not forward VTP packets on trunks.