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routing and linking offices

p cook
Occasional Visitor

routing and linking offices

Hi All, I hope somebody can help this problem.

I have 2 offices that are linked together via a leased line, the leased line service also provides internet connection for both sites. We have a cisco router at each end of the leased line which is maintained by our ISP.

The problems we have been experiencing has been bandwidth issues, so we have installed a fibre connection from one building to the next as the buildings are quite close but not connected.

I am now faced with two connections one for the leased line route and one for the 1gb fibre, we have severs and workstations in both buildings and would like to use the fibre link for server etc traffic and the leased line for the internet traffic, but also we need a failsafe that should the fibre line break or stop working we need to route back through the lease line and vice versa to miantain connection to both of our offices.

We have a core edge switch in the main office with some 2848's in a nice chassis, and the remote office has a chassis with several 2848's. we use VLans and have several subnets running i beleave the default gateway is provided by our isp.

The fibre link comes into our comms room via cat6 using a media tranciever to make the install easier.

How can I setup routing on our switch to take into account of our new link and maintain the excisting link? .

Mohieddin Kharnoub
Honored Contributor

Re: routing and linking offices


Say you have 2 Vlans on each network, and each Vlan has its own IP subnet and routing switch.

Now lets separate the traffic you have:

1- Default route to Internet is through the Leased line.
This can be done on the Core switch by:
ip route a.b.c.d (Leased line router)

2- Connection to Second building is done by fiber,
So i assume that you have different Vlan (different IP subnet) on that location, and you want to route to it by using the Fiber (not the leased line)

so what you need is a static route on both sides for the other network
Say :
network1 Subnet:
network2 Subnet:

and of course you are linking both networks by fiber on a specific Vlan (say Management Vlan

On site1 you need on the routing switch this route:
ip route 192.168.1.x (IP address of management Vlan on routing switch in the second side)

And on site 2 add the route:
ip route 192.168.1.y (management Vlan ip on the routing switch in the first side)

Now what you achieve with that:
1- Internet goes through leased line.
2- Connection between sites is by Fiber.

Now for fail-over scenarios, you can use the leased line to link between both sides by adding Static routes with higher administrative distance on both sides

But you need a routing switch that is capable of that, and the 2800 series is not.

But you still can do it on the Router if you can access.

So on Site 1:
ip route 192.168.1.x [distance]

On site2:
ip route 192.168.1.y [distance]

Dynamic routing protocols like OSPF is also a good solution in this situation.

Good Luck !!!

Science for Everyone
p cook
Occasional Visitor

Re: routing and linking offices

Hi Mohieddin,

Thanks for the great help i have one question, as we have the core acting as the local default gateway what would be the best way to setup the static for both site taking into account of our default gateway.

Occasional Visitor

Re: routing and linking offices

I'd want to suggest MSTP, making a spanning tree for each VLAN which you've isolated already. Change weights on each link according to what you want (make VLAN for server span via fibre, Internet access via leased line).

This way each link will fail over to the other if necessary. Be cautious though - STP can get messy if you don't know what you're doing when modifying values.

I'd also swap those converters with miniGBICs instead which would give you a pure ProCurve link (and you'd better handle it if the fibre link drops).