Placement of Layer 3 3COM switch query


I work in a UK Secondary school and we are currently reviewing our network infrastructure. We have around 700 PC's connected via DLink switches (10/100) to a 3COM 4200 Series gig backbone. We have five wiring cabinets (or closets!) which are interconnected using gig fibre.

We have two server rooms which link to the gigbackbone using copper gigabit uplinks from the 3com kit in the wiring closets.

We have from time to time suffered with broadcast traffic bringing the whole network down amd I am concerned that we have rather a large broadcast domain (ie all 700 pc's).

As all our 3com switches support VLAN it is my intention to implement a VLAN for each department( ie English, Science etc) within school with tagged links between 3com switches to make each VLAN available across our network. Each vlan will consist of at least one unique subnet but no more than 3. Each subnet has no more than 32 hosts.

I have purchased a 3Com 3226 Layer 3 switch for routing between our VLANs. I intend to place this into one of our wiring cabs. My understanding is that this layer 3 switch will take care of all the VLAN routing needs for our Layer 2 4200 switches.

My question is do we need more than one Layer 3 switch? I am planning on buying another to place elsewhere on our LAN but I wonder whether there will be any benefit to this and also I am unsure as to how having two routers on the LAN will affect our Layer 2 switches.

Also, some of my users complain of slow login times and slow network access, typically this occurs in large IT suites with 30 machines connected to a

100MB switch with a 100MB uplink to our gigbackbone. I am thinking of upgrading the uplink to each large suite to gigabit, at about £110 or $170 is this a worthwhile upgrade? I read an earlier post where someone said that networks don't really make full use of 100MB

Can anyone comment on this. Clearly I fairly new to this but I am trying to plan ahead for a reliable resiliant network. Feedback and comments much appreciated.


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