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New Member

Spanning tree problem


I have a mesh formed by a cisco 6006 and two cisco 4006 switches. In this setup one of my cisco 4006 is acting as a root switch by election. I have not done anything regarding this root switch configuration. When I connect a cisco 1900 switch with lower mac address to cisco 6006 switch, It has taken the 1900 series switch as root switch and starting reconstructing the path. The other cisco 4006 switch in the mesh is also given the cisco 1900 series as root switch. I have disconnected the 1900 series switch from the network. All the vlan configurations are done in cicso 6006 switch.

What could be the impact if the cisco 1900 series switch acts as root switch in the Network and How can I elimiate the election of cisco 1900 series switch as root switch.

Thanks in advance.

New Member

Re: Spanning tree problem


That has impact and results in sub-optimal topology in your network. Make sure Cat6006 is Spanning tree root by applying the below command.

If you are using cat OS

set spanning root

You can also use VLAN range to make this root for only selected VLANs

If you dont want to modify the configuration on cat6K then you increase spanning tree priority on other switches connected to it to make cat 6K as spanning tree root switch.

Re: Spanning tree problem

You can issue "spantree priority 0" under the interface config of the 1900 interface connected to the rest of the network to make 1900 ineligible to be root. When determining location of the root switch you should consider traffic flows. Basically if most of the traffic for a VLAN is originating or terminating on the 6006, it's better to manually set 6006 as the root switch. On 6006 try "set spatree root dia 3" command in which vlan_id is the vlan for which you want this switch to be the root.



Re: Spanning tree problem

you can elimiate the election of 1900 being elected the root switch by increasing the bridge priority. Or you can issue set spantree root command on the switch you want to make the root switch (this will decrease the bridge priority on the switch). From your setup I would think you want the 6006 to be the root switch.

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