Case Studies

Microwave link, tunnelled PI space

The Challenge

A customer with premises on the top floor of a towerblock in Berkshire has a line-of-sight microwave link to the roof of a Datacentre. Whilst the datacentre provides good up and downstream bandwidth, the customer wished to have a legacy /23 of PI (Provider Independent) IPv4 space from RIPE routed to the connection, as well as IPv6 (which the datacentre had not yet the ability to provide directly). The customer also had no resilience, and wished to be able to fail over to an ADSL backup, whilst maintaining the IPv4 and IPv6 blocks and routing.

The Solution

Initially an FB2700, later upgraded to an FB2900, configured to run an L2TP tunnel back to Andrews & Arnold's Telehouse LNS cluster which carries the IPv4 and IPv6. The Firebrick has 3 separate routing tables, one carrying the payload of the L2TP tunnel, 1 for the microwave link and 1 for the ADSL backup. Ordinarily the microwave link is favoured for carriage of the L2TP tunnel. Should that fail, routing falls back onto the ADSL. In addition the FireBrick also does firewalling on IPv4 and IPv6.

More Info

Although this case study is not a particularly complex one, one of the side-benefits to the implementation of the Firebrick in this usage case was when the datacentre providing the transit over the microwave link had packet loss and latency problems. Using the graphs the Firebrick generated, these were much more readily diagnosed, and found to be a software issue on a router in the datacentre's core network.

Microwave link tunnelled IP address project

Features Used

Tunnels (100)


Using the FB2900 as a L2TP client, it's able to connect through to AAISP's L2TP service.



The ADSL failover uses PPP



Profiles can change much of what the FireBrick does based on time, pings and so on. In this case, profiles monitors the microwave connection to the local datacentre and changes the routing over to ADSL in the case of failure.


Routing Tables

Separate routing tables are used for the multiple internet connections



IPv4 and IPv6 firewall rules are in place

(All the network diagrams on these case study pages are very rough representations and are not an accurate representation of live networks)

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