Adding New Switch

[tahirs001]

Hi,

We are going to connect a new switch to our LAN in our PLC office.  The PLC office has 3 switches connected together using the gig ports and SFP connectors.  We are going to connect the new switch using a single crossover cable and are going to connect it during business hours so need to make sure there is no downtime and that we do not kick off a spanning tree election.

This site is connected back to our data centre by 2 X 100MB LES connections set up as an etherchannel and connect directly into our core switches in the data centre.

Since I am being told to do this during business hours I plan to disable spanning tree on the new switch using the “no spanning-tree vlan” command and I will also use the “spanning-tree vlan … priority 61440” command incase to make sure it never becomes the root bridge.  I know its not a good idea to disable spanning tree but because we are doing it during business hours and because the site is directly connected to our core data centre switches using etherchannel I don’t want to take any extra risks.

Any ideas how this should be done without causing distruption?

Thanks

Tahir

[Mohamed Sobair · Accepted solution]

Hi,

You dont need to disable Spanning-tree on the New Switch, In fact doing So might be the real risk , cause you could simply introduce loop into your netwrok.

I would recommend you do the following befor you add the New Switch:

1- Ensure you Manullay Inherit /set the priority in the root bridge to 0.

2- Configure (Spanning-tree guard root) in root bridge designated ports (Uplink ports toward other Switches).

3- If you have a VTP domain running, make sure the New Switch set to be in client or transparent mode.

That should suffice for you, and you wont have any STP kick off.

Regards,

Mohamed