12-29-2008 08:48 AM - edited 03-06-2019 03:10 AM
I inherited a network and see some odd configurations that I don't normally do and can't think of a reason for it. One of them has the following statements
spanning-tree uplinkfast
no spanning-tree vlan 20
no spanning-tree vlan 27
no spanning-tree vlan 90
Is there a reason anyone could think of for this?
Solved! Go to Solution.
12-29-2008 12:25 PM
Hello Roland,
in this case I strongly recommend to enable STP on all Vlans in use even if they are at the moment confined in a single switch.
I agree that this configuration is not logical and unsafe.
Hope to help
Giuseppe
12-29-2008 09:09 AM
Hello Roland,
be aware that in low end Cisco Switches there is a limit in the number of STP instances that can run on the device.
There is a limit in the maximum number of vlans that can be defined but it can be higher.
To make an example I used some 29xx there was a max STP instances of 64 and a max vlans of 128.
Vlans in excess of first number can be defined but their STP instance is automatically disabled so you can see a configuration like that even without a human configuration.
You can check how many vlans are defined on the switch with
sh vlan
and status of STP with
sh spanning-tree summary
There was a similar thread some mounths ago with the same scenario: someone starting to manage a network with this kind of strange commands combination
Hope to help
Giuseppe
12-29-2008 11:42 AM
Thanks Giuseppe but that's not the case here, we have 15 VLAN's on these switches and the ones with STP turned off are actually being used.
I can't think of any real reason my predecessor would do something like this other than misunderstanding the UplinkFast functionality.
12-29-2008 12:25 PM
Hello Roland,
in this case I strongly recommend to enable STP on all Vlans in use even if they are at the moment confined in a single switch.
I agree that this configuration is not logical and unsafe.
Hope to help
Giuseppe
12-29-2008 12:38 PM
Thanks for the confirmation. I thought I might be missing something but it's nice to get a sanity check.
Find answers to your questions by entering keywords or phrases in the Search bar above. New here? Use these resources to familiarize yourself with the community: