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Hi I am looking for some advice and best practices for the contingency plan of our Fibre Link data connection between Offices and the Warehouse which is approximately 100 metres away over a river but technically still on the same site.

I will outline our setup:

Both Domain Controllers are in our offices and devices in the WH rely on the Fibre Link to talk to the logon Server and provide connectivity for all services DNS/DHCP/Internet/SQL/Fileserver shares etc.

Computers / Devices in the Warehouse include:

  1. 24 Port Netgear Smart Switch assigned IP 10.0.0.50 (8Port POE Switch also connected for the Access points)
  2. 7x PC’s on DHCP
  3. 1x SQL Mirror Replication Server
  4. Large Multi-Function Photo Copier that prints all of the Picking Lists / Dispatch Notes / Product Instructions
  5. A few other Network Printers
  6. 5x POE Wireless Access points with reserved static IPs
  7. 4x Wireless Barcode Scanners with Static IP’s that connect via the AP’s (USB Scanners to fallback on in the event of the Wireless network/Scanners being unavailable)

There is actually 2 working fibre links, so if one fails we have the other, but if both fail / get cut or whatever we currently do not have a proper contingency plan in place.

We are still able to print all documentation and do the processing in the Office as a last resort.

We were proposing to purchase a router with USB/SIM 3G/4G Modem Support, to provide internet access which should at least allow at the minimum PCs to each login locally connect via VPN and grant Application and SQL connectivity for the Warehouse Management Package and Despatching Software.

But if the Warehouse Switch is assigned an IP of 10.0.0.50 configured for our network and then the fibre link is disconnected, what happens if this is then plugged directly in to a router? I assume this router should be configured as a DHCP Server? What other configuration will be required for the router and switch?

Should there also be a need to promote the SQL Mirror server to a Domain Controller?

What other alternatives would be easy to implement to maintain as much service level as possible?

Thanks in advance

Rld
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    I don't think I'd plan for contingencies in this case. Who owns the fiber? – ewwhite May 07 '15 at 15:06
  • `There is actually 2 working fibre links, so if one fails we have the other, but if both fail / get cut or whatever we currently do not have a proper contingency plan in place.` - What if you get a third connection method and all three fail? Then you'll need a fourth, but what if that fails? Ad nauseam. I don't think I'd plan for anything more than what you've already got. – joeqwerty May 07 '15 at 15:32
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    If both of the independent and physically separated fiber optic links go down, chances are that your building isn't going to be in good shape either. – Hyppy May 07 '15 at 15:33
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    Also, do you have a history of problems with this fiber? If it's managed by a third party with failover already built-in, you may be overthinking/overengineering the solution. – ewwhite May 07 '15 at 15:36
  • There is no real history of problems, and the connection has been solid for years, we are just currently reviewing our entire Business Contingency and Disaster Recovery and hoping to strengthen where weaknesses exist. The fibre cables actually run down the side of the building are suspended in the air on some metal beam that crosses over the river. The fear is that these are not particularly well protected are within reach and the site is not closed to the public. – Rld May 07 '15 at 16:14
  • ..and it would not be particularly difficult for somebody who really wanted to vandalise the property to break this link. – Rld May 07 '15 at 16:23
  • I don't think it's worth the effort, but if that's the area the business wants to focus on, go for it. If anything, you should have identical switches on both sides and monitoring of the link. – ewwhite May 07 '15 at 16:39

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Do you have line-of-sight between the buildings? Why not implement a wireless link using something like 2 Ubiquiti Nanostation 5 (NSM5) devices. If you're ok with manually swapping over to the wireless link thats an option but it would be best to have smarter switches (Layer3) which allow you to assign a priority/cost to the links (Fibre v wireless) so you can have automated failover. You should also implement monitoring so if the ports that the fibre connections are connected to go down that an alert is sent to investigate why - this is just so you're not working off the wireless link for months without knowing that there's a problem with the fibre. Are the fibre connections configured using link aggregation where the two connections are paired to form a higher bandwidth connection? If you create two links between two switches without link aggregation (known as EtherChannel on Cisco switches) or the use of spanning tree protocol you could introduce the problem of a loop on the network.

Evolutionise
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  • To answer the question regarding Link Aggregation, we have attempted this but I believe came to the conclusion that the 2 different switches were of different models and may be presenting an issue achieving this. We proved both links worked separately and all fibre modules worked, the speed of a single link is acceptable for the bandwidth required between here and the warehouse also. – Rld May 07 '15 at 16:24
  • The 2 sites are within the line-of-sight. How expensive would this be? We was really looking at a cost effective solution that wouldn't cost thousands of pounds for hardware, but hearing what options are available to us is still appreciated. – Rld May 07 '15 at 16:27
  • Two Ubiquiti NSM5's can be purchased from Amazon UK for £120 and have a range of up to 15KM. – Evolutionise May 07 '15 at 18:28
  • If you want to keep the cost down on a router to do link failover, I would advise looking at Mikrotik. Someone on a Microtik forum may be able to best advise you as to the configuration. – Evolutionise May 07 '15 at 18:39