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Add VTP and a 1760 router

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Net layout 032407

Maintaining a VLAN database is much easier using VTP, but requires some care about adding a new switch, else it might wipe out your carefully configured VLANS.

I presumed the best way was to setup ONE switch, zap the other switches revision numbers to zero, and then hook them up. But I could have hooked them all up first and then configured. Switches after THAT would have needed to have their revision # set back.

I planned to incorporate the router right into the load balanced, fault tolerant MST (Multiple Spanning Tree) switch network, but ran into a glitch when it came to the router switch ports. The switch banks added into a 1760 router are NOT full function switches, lacking any but VTP transparent mode and NO facility for any STP other than standard. Odd since the IEEE has deprecated STP in lieu of Rapid STP.

I was able to configure the router switch port, a vlan (10) to serve as an IP addressable gateway, a finally ping out to another network ( No small feat since this required the config of the PIX 501 firewall appliances with a static route back to my net. I did get into the config of the PIX enough to see that OSPF routing protocol could be configured to make this simpler and more flexible.

Questions I still have:

An IP is listed for “who” updates VTP on the switch (see note marked ** below). Since the switches update themselves (presumably with layer 2 multicasts) I’m not sure why a layer 3 IP would be important.

VTP Setup.

Let’s take a look at the initial state of VPT on the 3550 switch that I chose to be the “leader” Read the rest of this entry »


Written by scottledyard

2007, March 25th at 10:00 am

Posted in CCNP, Cisco, Cisco Switches, MST, RSTP, STP

Cisco switches: Classic STP -> RSTP -> MST

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To better use switch connections that are otherwise blocked by STP, I setup 5 switches (2 distribution and 2+1 access) to support 7 VLANs with redundant links for fault tolerance.
Traditional CSTP provided for convergence after a link failed, in 52 seconds. RSTP amazingly reduced that to sub-second convergence. MST maintained that, but the lab will continue next time to carry the 7 VLANs over two different virutual switch topologies. (I did NOT use VTP with this work.) Read the rest of this entry »

Written by scottledyard

2007, March 18th at 1:37 pm

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