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Internet is working only on VLAN 1



I  need to connect two switches with each have different Vlans and wants  to Connect the users of These Switches to Existing Network of  Company(Vlan 1 ; showing Right in the picture).

I  have created Vlans and able to route packets from Two Vlans (10,20) to  VLAN 1 but i am unable to get access to Users existing in vlan 10,20.

Internet  is working fine from VLAN1 and existing network did not have any router  ,it is just a DSL modem and did not have Static /Default Route  option,NAT.

What Option should i choose for it.

3750x have 12 Mini Gbic Slots and 1 Routed port and did not have any NAT options in it.

Please find the attached image and guide me,I am thankful to you.


Daniel Boling


The right side of you topology has worked in the past because you did not need the ability to route between VLANs.  I would either introduce a router or switch capable of NAT/PAT and 802.1Q, or connect the DSL modem to your 3750 on the right side of the topology.  As your VLAN numbering in the topology conflicts with the text in your question, I'll be referring to the topology.

The latter suggestion is to connect the modem directly to the right (direction) Catalyst 3750 switch, enable Layer-3 functionality on that port and configure trunking on all interfaces connecting the switches.  From there, you can define VLANs 2 and 3 in the local VLAN database, configure a VTP domain and distribute the information to the rest of the Catalyst switches. 

Consider refining your approach to the solution.  Notice that VLANs 2 and 3 are on the left side of the topology.  If they have to communicate, be sure to configure the left 3750 switch accordingly, or the traffic will have to cross over to the right (direction) 3750 before being routed back to the left side. 

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