Why cannot configure link-state tracking on C3020 gi0/24?

[northwindsy]

Hi guys,

I'm planning to configure link-state tracking on our C3020 blade switches. The topology: 2 blade switches both use Gi0/24 to connect CORs separately as upstream links, and some trunk ports going down to cloud, no ether channel. The plan is to add a tracking group on each, so when Gi0/24 goes down the blade switch should shut down the downstream trunk ports, thus the traffic for cloud will be forced to go to the other blade switch with good uplink.

However there's one question, based on this link (near the bottom):

http://www.cisco.com/c/en/us/td/docs/switches/blades/3020/software/release/12-2_55_se/configuration/guide/3020_scg/swethchl.html

Gi0/24 cannot be in a tracking group or it'll cause problem? And to be honest I think this article looks pretty confusing, cause it says:

Do not configure a cross-connect interface (gi0/23 or gi0/24) as a member of a link-state group.

and:

Only interfaces gi0/17 through gi0/24 can be configured as upstream ports in a specific link-state group.

So my question is: Why gi0/24 can be, but cannot be in a link-state group? Which one is correct among these 2?

If it cannot be configured for link-state tracking, what will be my best other choice?

Might a dumb question but I don't have the environment to test it, so any advice will be much appreciated.

[Steve Fuller · Accepted solution]

Hi,

I think the answer is in Dual-Purpose Uplink Ports section of the Configuring Interface Characteristics section of the configuration guide.

Ports 23x and 24x are different from the other dual-purpose ports. When operating in external mode, these ports are single, uplink 10/100/1000BASE-T copper Gigabit Ethernet ports. When operating in internal mode, they use the 1000BASE-X mode, and they form a cross-connection with a switch that is installed in a corresponding module bay in the blade server.

I've not used link tracking on those particular interfaces so I don't know whether it can be configured and actually works and this is more of a warning, or if it will not actually track correctly.

I think this would be something you should test as part enabling the feature.

Regards

[northwindsy]

Thanks Steve, that seems the reason from what Cisco says. Anyway I'm gonna use 21 and 22 to form an etherchannel for uplink so we don't need to worry about issue with 23 and 24.

Cheers,