intervaln config

Unanswered Question
Nov 2nd, 2007


I need some help to configure my network properly. i have layer 3 switch 3750 which is the core switch for my netwrok and other switches some cisco and some 3-com switches 48 vlans has been configured yet.

i am using class c network id for all clients and as well as servers. to control the broadcast now i want to configure vlans for 3750 switch

1- i want to create vlan only on 3750 switch each port should be in diffrent vlan.

2- network id will be changed for clients and servers so routing has to be enable on 3750 switch.

3- how i can define routing on 3750 switch so it can route all traffic from all vlans to building2 coz i dont have any layer 3 switch in building2.

clients are not configured for firewall.only isa2006 is configured to firewall. clients are using internet throug isa2006.

I have this problem too.
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Jon Marshall Fri, 11/02/2007 - 07:35


Do you really want a vlan per port ?. You can do this if you want to but there is nothing wrong with having multiple ports in the same vlan.

Anyway to define a vlan at layer 2 on your 3750

3750(config)# vlan 10 name v10

This will create a layer 2 vlan.

To create a layer 3 interface for the vlan

3750(config)# interface vlan 10

3750(config-if)# ip address

3750(config-if)# no shut

to enable routing on the 3750 use the "ip routing" command.

As for building 2. If you only have a single vlan in building 2 eg vlan 50 you would

1) Create the vlan 50 at layer 2 on the 2950.

2) Create the L3 interface for vlan 50 on the 3750 (see above for example)

3) Put the ports that connect the 2950 to the 3750 in vlan 50.

If you have multiple vlans in bulding 2

1) Make the 3750 a VTP server.

2) Make the 2950 a VTP client.

3) Configure the link between the 3750 and the 2950 as a trunk.

4) Create all the L3 vlan interfaces on the 3750.



kashifashraf Fri, 11/02/2007 - 08:01

Thanks for your reply it realy helped me a lot.

for testing i configure 3 vlan in 3750 switch and i configured ip routing also within the 3750 switch routing is working fine but if i am trying to reach client which is in another building i cant reach there.

how can i define routing on 3750 switch so it can route data to buliding 2 switch.

Jon Marshall Fri, 11/02/2007 - 08:03

Couple of things

How is the other buidling connected to your 3750 switch ?

What vlan is the client in in the other building.

Have a look at previous post which suggests 2 ways to connect up other buildings.


kashifashraf Fri, 11/02/2007 - 08:09

building 1 3750 switch SFP-LX 1000BASE tx connected to building 2 2950 switch 1000BASE LX. ports are configured as a trunk so.

building 2 switch is in default vlan1.

Jon Marshall Fri, 11/02/2007 - 08:12

So when you do a "sh vlan" on teh 2950 do you see the same vlans as on the 3750. Have you setup VTP ?

If all the ports are in vlan 1 do you have a L3 vlan 1 interface on the 3750 and does the client that is on the 2950 have it's default gateway set to the vlan 1 interface on the 3750 ?


kashifashraf Fri, 11/02/2007 - 08:19

vlan 1 is configured on both switches.

clients from 2950 switch can communicate with clients on all vlans in 3750 switch. and clients which are in 3750 switch can communicated with each other on diffrent vlans but cannot communicate clients which are in building 2 2950 swtich.

defalut gateway is configured on all clients.

kashifashraf Sat, 11/03/2007 - 04:55


i followed your suggestion properly and its working now.

thanks for your suggestion its working now.



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