I have a network consisting of three servers in a data center, all of which are connected to each other via a switch.

In addition to this I need this network to access 4 additional networks, most of which are provided via cross connects to other data centers, as well as the Internet.

Basically the networks are as follows:

  • LocalNetwork (
  • Equinex (
  • Atrium (
  • Internet (...)
  • HongKong (

I have hired a network professional to give advice but his solution involved 3 routers which individually cost 1200 dollars a piece and a switch and it's still having issues.

I am not a network professional myself, only a developer, but I believe as though this should only require one single switch to connect the three server computers together to form LocalNetwork, and one single router to connect the 5 networks together.

My issue is that every router I've seen seems to just be a switch with one WAN port to connect to the Internet. Is there not an example of a basic router that has say 5 or more ports in it that allow me to connect 5 networks together? Can I not just solve this problem with a single switch and a single router?

8 Answers 8


3 routers sounds like overkill to me but it would be interesting to see the topology and hear him explain the reason behind it.

Depending on your requirements for redundancy and/or loadbalancing a 1921/1941 could be fine for your needs. That would be only one device because it has both routing and switching if you stick a HWIC Etherswitch card in it.

The high availability design would be to have two routers and two switches but then the servers should be dually connected as well.


If all of these networks are already being brought to a central location via different circuits/cross connects, you could certainly connect them via one router with 5 different ethernet interfaces.

The specific model of router would greatly depend on the throughput needs. That is to say, if there is to be a large amount of traffic between these networks, you would require a higher end router to handle the traffic volume effectively.

Something in Cisco's ASR1000 or 3900 product lines might be appropriate here, again depending on your throughput needs.

However, several of those networks you reference aren't publicly routable addresses. You will need to do some form of NAT to reach the internet at least, and possibly your "Atrium (" network as well.

You would also most likely want a firewall providing NATing/security between your internal networks and the Internet.

Long story short, it could be done with one switch and one router, but there is probably a need for more devices to create the optimal solution. Without specifics about your business case, throughput needs, etc. it is hard to give a more detailed answer.


Technically one router and one switch should be sufficient, ideally you should have two switches and two routers (as redundancy). Also it should not be an issue to install several network cards into the router, however 1.200 isn't considered a lot of money for a decent professional router, so it might be that these routers do not support expanding the network sites. What you might consider doing is purchasing one or several layer 3 switches instead (switches which function at layer 2 and 3, so also allowing basic routing)


To get to the heart of your question, a single L3 (layer 3) switch could do what you want and be divided into logical networks via VLANs and the switch will handle the routing between the networks though this is far from an optimal solution. Each VLAN interface will have an IP address configured which becomes the default gateway for all devices it serves. Although not recommended for several reasons with security at the top, your Internet connection could even technically connect on the same switch and work, but that's asking for trouble; I'm sure this is why your consultant recommended at least 1 switch and and 1 router so the two are separated. You really should have a firewall between the two or at least firewalling functionality on your router.

Ideally, you would hare pairs routers, firewalls, and switches for redundancy and separation of functions to provide security boundaries.


Maybe this can work--

Devices required: 2 switches (A,B) 1 router (R)

Switch A is where we connect the servers-- connect switch A to the router-R on interface-1. On the router-R, interface-2 we have to create subinterfaces for other 4 networks. Put them in seperate vlans.

For example:

  • Equinex ( -- VLAN 20
  • Atrium ( -- VLAN 30
  • Internet (...) -- VLAN 40
  • HongKong ( -- VLAN 50

Connect router-R interface-2 to the switch-B. And then connect the Handoffs from All 4 networks to the Switch-B and configure them in specified vlan above.

Above should work with a single switch and a single router.

However-- where is the firewall in the network? this really needs one. What kind of handoffs are the other 4 networks. If there is a T1 you will need a T1 card for the router.


Did your initial requirements include a cost limit? The device count might seem high, however $1200 is very cheap with regards to network equipment. You could use one device to solve the problem but you will need a device that supports different modules, higher port count, different licenses, etc. The more flexible the network device, the higher the cost. What model/brand of router is used in your solution?


My solution would be:

Two cheapish switches - ie ones that support LAG and STP. Say a pair of 8 port Netgears GS110s. They are around £65 each.

1 router/firewall - that will be a PC class system with a quad port NIC in it to augment the built in NIC. However if you don't need individual GB connectivity to the remote sites then a single NIC can be used with multiple VLANs (the cheapy switches will support this). The PC will be running pfSense (free - Open Source - http://www.pfsense.org/)

pfSense supports clustering, so run two of them. For rack mounting - get a cheap pizza box 1U thing from Dell or whoever.

Total cost: 2 x £65 + 2 x £339 (Dell R210 11) + VAT etc. OK that's around USD1K

That gives a hefty amount of thoughput, functionality and redundancy. Halve the price and hardware and still get the job done but without the redundancy.

pfSense can happily shuffle packets at GB speeds on that class of system and have enough power to do say IPSEC without breaking a sweat. There are loads of add on packages for it as well but frankly the built in functionality is more than enough for most people. No license fees.

The web interface is pretty easy to get around and is no harder than a home router but there is rather more in the box!

Cheers Jon


We can implement this network topology with single router and single switch (layer 2 switch )

In router configuration

Router(config)# int ethernet gigabit 0/1 # ip address 255.255 .255.0 #no shutdown

Router(config)# int ethernet gigabit 1/1 #no ip address #no shutdown

Router(config)#int ethernet gigabit 1/1.10 # encapsulation dot1q 10 # ip address /for local network/ #no shutdown`

Router (config)#int ethernet gigabit 1/1.20 #encapsulation dot1q 20 #ip address #no shutdown

Router(config)#int ethernet gigabit 1/1.30 #encapsulation dot1q 30 #ip address #no shutdown

Router (config) int ethernet gigabit 1/2 #ip address x.x.x.x x.x.x.x /*isp public address*/ #no shutdown

Router (config t)# ip route 0.0.0.O pointing towards gateway of isp

access -list 10 permit ip any

IP NAT inside soure list 10 interface ethernet gigabit 1/2 overload

Switch configuration

Switch(config)# int f0/1 = /*link connecting to router interface ethernet gigabit 1/1 */ # switch port trunk # switch port trunk allowed vlans all #no shutdown`

Switch(config)# int f0/2. /*Link connect to other end switch with is in offshore location*/ #switch port mode access #switch Port access vlan10 #no shutdown

Switch (config) # int f0/3)/*link connect to other end layer2 switch with ofshore location*/ Switch port mode access Switch access Vlan20 # no shut

Switch (configt)#int f0/4 Switchport mode access #switchport access Vlan30 No shutdown /*link connect to other end of layer2 switch in ofshore location*/

*You can connect three server to same switch create another vlan 40"

I hope for your requirement this topology will suits with single router and switch. You can even restrict traffic between vlan 10,20,30,40 with access-list configuration in router

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