March 16, 2009 by ted.

This past week, I configured our 2 Nexus 7000 boxes to take advantage of the new Virtual Portchannel (vPC) feature.

Here’s some info on this feature ::

http://www.cisco.com/en/US/prod/collateral/switches/ps9441/ps9402/white_paper_c11-516396.html

Config Guide

If you read my article about VSS technology, then the benefits with virtual portchannels are pretty much the same. One major difference is that the two Nexus boxes are still very much separate unlike using VSS. You still no longer need to worry about Spanning-tree. One thing that wont change from how you are probably doing things today is the HSRP configuration. You will still have your active and standby HSRP devices. The trick here is that when you dual home to the distribution, you use only one portchannel at the access side. Your access switch will dynamically load balance across both links using standard portchannel load balancing algorithms. The thing to remember is that packets received by the standby HSRP device are actually forwarded. So in a sense, you have a “active-active” HSRP state in the background.

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March 9, 2009 by ted.

Last week I converted our new distribution to VSS. If you haven’t heard anything about Cisco VSS yet, you should check it out. VSS is used on the 6500 chassis if you have the new VS-S720-10G-3C supervisor. The concept of VSS is pretty easy to understand. If you are familiar with stacking 3750 switches, you will understand VSS. Basically, you take two 6500s and make them look like only a single switch to anything that connects to them.

Some reasons to use VSS are to get rid of spanning-tree between the distribution and access layers. You also no longer need to use HSRP. For example, an access switch connecting to your distribution would usually be dual-homed, meaning connecting to two separate distribution switches. With spanning-tree, in most cases, one of the uplinks will be unused for a given vlan. That means if you use 10 Gig uplinks, one is unused and only for redundancy (you can balance vlans to even things out, but that has to be configured). With VSS your access switch would have only one port channel that would actually connect to both distribution switches. From the perspective of the access switch, it’s only connecting to a single switch (even though it’s physically two separate switches). Since we only have one port-channel to the distribution, HSRP or VRRP is not needed. One vlan IP is assigned to the VSS distribution switch, and clients use that as default gw. Load balancing across links is done using the traditional etherchannel hashing algorithm.

Check out http://cisco.com/go/vss

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February 20, 2009 by ted.

I decided to upgrade our two Nexus boxes to the latest code before putting them on the network. The procedure is a bit different compared to a regular IOS upgrade. You need to download two files– the NX-OS image, and the “kickstart” image that corresponds to it. I chose to connect to the management port on the supervisor to upload the image. It’s in its own vrf so don’t forget that when trying to ping, etc.

Here is the process below as I did it ::

switch(config)# inter mgmt 0
switch(config-if)# ip address 1.1.1.2 255.0.0.0
switch(config-if)# no shut
switch(config-if)# end

switch# ping 1.1.1.1 vrf management

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