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3750G-12S callapsed core/distribution config


I'm trying to configure 2 x 3750G-12S switches as core or callapsed core/distribution switches. I have never done this before and would like someones advise on the best configuration please?

My thoughts are having 6 Vlans 1,10,20,30,40,50 each connecting to a switch block consisting of 3560G,3500 and 2960G switches (access layer). These are linked together in a daisy chain fashion and connect back to both 3750G (Core/Distribution) switches via fibre on the top and bottom switches in the block/stack (Obviously there will be 5 or 6 switch blocks).

By putting all sw blocks in a seperate Vlans, how do I control stp? - I was advised to have half the vlans using "core_sw_1" as a root for stp and the other half using "core_sw_2", thus sharing the load, but have not worked out how to achieve this!

I no that the cores are running in PVST mode by default. I have tried to configure vlan 1,10,20 to use core 1 as the root for stp but the "set spantree" or "set spanning-tree" command is not recognised, what commands do i use? or what should I do to set the core switch as root on the grouped vlans?

Please give me as much advise as possible!!

Many thanks



Re: 3750G-12S callapsed core/distribution config


If you only require one vlan in each switch block then all you will need to do is ;

config vtp mode transparent on all switches

config all vlans on both core switches

config single vlan on each switch block

then you will have a trunk uplink from the first edge switch on each block to first core switch, and another trunk from second edge switch on each block to second core switch,

then for the first block vlan, config first core switch as root, for the second block vlan config second core switch as root, for the third block vlan config first core switch as root and so on

so you will have one switch block using link to first core switch as root port and the next switch block using the uplink to second core switch as root

set commands are only valid on older CATOS switches, your 3750's will run IOS, check out the config guide from here;

Your end topology should be like;


CORE1------BLOCKAsw1 VLAN 10

| |

| |

| |

CORE2-----$-BLOCKAsw2 VLAN 10

CORE1----$--BLOCKBsw1 VLAN 20

| |

| |

| |

CORE2------BLOCKBsw2 VLAN 20


Where $ means this port is blocked. Once you config STP priority correctly the switches will do this automatically.

You should also check out running Rapid STP.but that can be the next project.



Super Bronze

Re: 3750G-12S callapsed core/distribution config

With the 3750 series, you do have the option of just having one core/distribution device.

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