VLANS connection between two cisco catalyst 3750 switches

I have two cisco catalyst WS-C3750V2-24TS-S    switches

both have vlans 100 and 200

how do I configure the switches to allow vlan 100 from switch A to connect with vlan 100 in switch B and vice versa (and the same for vlan 200) ?

VTP - Vlan trunking protocol is your friend!

show vtp stat - this will show you what your current vtp settings are.

e.g

3750a#sh vtp stat

VTP Version                     : running VTP1 (VTP2 capable)

Configuration Revision          : 33

Maximum VLANs supported locally : 1005

Number of existing VLANs        : 23

VTP Operating Mode              : Client

VTP Domain Name                 : CISCO_LAB_Domain

VTP Pruning Mode                : Disabled

VTP V2 Mode                     : Disabled

Next, set vtp domain (exact same on both devices, is case sensitive)

(config)#vtp domain CISCO_LAB_Domain

(each other connected switch in a vtp default state should automatically pickup this new vtp domain, otherwise, you may need to individually set it.)

next thing you want to do is set your vtp operating mode for each device. One should be client, one should be a server.

(config)#vtp mode client  <or> #vtp mode server

Next, if needed (and it rarely is) a vtp domain password on each device

(config)# vtp password 12345cisco

vtp is set, now edit vlans by changing them on the server and they will then propogate to the client devices.

!Warning! - if you put a new device onto your network in 'vtp server' mode AND it has a higher revision number, it will wipe out and re-write your vlans to whatever it has in its vlan database!

Before adding a new switch, always make sure of its vtp settings before bringing it online!

It is considered best practice to only edit vlan data on the vtp 'server' which you usually only have one or two of i.e. your core switch.

It is not necessary to set up VTP, although it makes managing VLANs easier:  If you create a VLAN on one switch (the server), it is automatically created on the other switch as well.  But VTP will not automatically set up trunk interfaces between the switches, which is required to carry more than one vlan on the same physical link.

You will have to set-up trunking on the link between the two WS-C3750V2-48TS-S    switches.  Run the following commands on both switches, on the interfaces that connect to each other:

conf t

int <Type&Number>

 switchport trunk encapsulation dot1q

 switchport mode trunk