I have a network topology like bellow:

In the server A(left), I want to access the Server B(right). But in A there only two network interface, and they are all import, so I can not change any of them, it also impossible to add a network interface, I want to access the of server B, how can I realize this?

I heard about the route cross VLAN, but I don't know what's it, and hot to config, who can tell me the detail of it?

  • 3
    Routers route between networks. You either need a router, or a layer-3 switch (layer-2 switch that has a routing module). Layer-2 switches cannot route between networks.
    – Ron Maupin
    May 27, 2019 at 12:34
  • Hello. I wrote an article which discusses the options available for Routing between VLANs (also known as "Inter VLAN Routing"). I think it would help you.
    – Eddie
    May 27, 2019 at 17:55
  • Using a Layer-3 device such as a router or a layer-3 switch is the simplest way to route between networks. However, some operating systems allow for routing between Network Interfaces. Microsoft describes enabling the feature here. support.microsoft.com/en-us/help/323339/… In addition, static routes would need to be installed.
    – TDurden
    May 28, 2019 at 16:24
  • Did any answer help you? If so, you should accept the answer so that the question doesn't keep popping up forever, looking for an answer. Alternatively, you can provide and accept your own answer.
    – Ron Maupin
    Dec 15, 2019 at 3:29

1 Answer 1


You need to configure InterVLAN Routing between your VLANs. There are three type of methods are available to configure InterVLAN Routing.

Recommended way is configuring routing in your Switch and switch must be a layer 3 switch.

I assume that your switch is Layer 3 and Cisco switch.

You need to configure SVI on Switch

Interface VLAN2
 ip address
no sh

Interface VLAN3 
ip address  
no sh

Interface VLAN4 
ip address
no sh

(You can use your any IP address as per your requirement) Then You can configure route between Networks

Ip routing
Ip route 

Additionally SVI Ip address should be Default gateway of your NIC. If you want to access Other networks, You need to configure Static route between those networks.

In addition to that you can use separate router for this configurations. If you use separate router you can need to configure separate connectivity between router and Switch, In your problem it is possible because it has only three VLANs. If there are many VLANs in your network, this method will generate additional overhead and complexity.

Third method is sub interface configuration between router and switch. In this situation we need only one link between switch and router. But Sub interfaces needs to create on router..

  • Consider that if you are going to mention three methods, you should describe them, at least briefly. Especially consider that the OP or future readers may not have layer 3 switches.
    – Ron Trunk
    May 27, 2019 at 11:53
  • Even with a layer-3 Cisco switch, you may need to enable routing with the ip routing command. That is a source of frustration we often see here.
    – Ron Maupin
    May 27, 2019 at 12:35
  • @RonMaupin I think, ip routing is enabled by default
    – infra
    May 27, 2019 at 15:05
  • Not on all Cisco layer-3 switches. We have had many questions here where the answer was to simply enable routing on the layer-3 switch because that was not the default. More recent models typically have that as the default, but not all do, and it was certainly not the default in the past.
    – Ron Maupin
    May 27, 2019 at 15:08
  • @RonMaupin Thanks for your information. Edited...
    – infra
    May 27, 2019 at 15:18

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