Virtual Leased Line: Several Connections, One Fixed Link

On the left, the lines that are available on site anyway: one or more mobile networks, DSL or cable, and Starlink if needed. In the middle, the bonding router, which spreads every data stream packet by packet across all active lines. On the right, the hub in the data center, which reassembles the packets in the right order and passes them on as one connection with a fixed IP address. To your applications the result looks like a single connection, except that no individual line can pull the plug on it any more.

A classic leased line is a dedicated carrier line between your site and a fixed point in the network: guaranteed bandwidth, a fixed IP address, one contract, one path. That single path is exactly its weakness. A digger, a fault in the carrier network or a problem in the building connection, and the site is offline.

A virtual leased line builds the same property, a reliable connection with a fixed address, out of several independent lines. The router on site splits the data stream into packets and spreads them across all lines at the same time. At the other end, on the hub in the data center, the packets are reassembled in the right order. An encrypted tunnel runs between router and hub; for everything behind it, the connection is a single access with one public IP address.

That is what sets bonding apart from simple failover and from load balancing. Failover only switches over once a line is dead and only ever uses one. Load balancing distributes individual sessions across different lines, but cannot speed up a single transfer and loses the session when the line changes. Bonding uses all lines for every transfer and keeps the session, because the tunnel to the hub stays up even when a line underneath drops out.

Many people do not know that lines can be bonded this way. Yet the technology is proven: the German broadcaster MDR, for example, uses Peplink routers to bond all available bandwidth for outside broadcasts. The same principle suits branch offices, construction sites or rural practices. Manufacturers call it bonding or SpeedFusion; for you the result is a leased line that does not hang on a single line.

Bonding is technology-independent. Anything that delivers an IP connection on site can be one path in the bundle:

• Mobile (LTE and 5G): flexible and available almost everywhere. Routers with several modems such as the Peplink MAX HD4 MBX 5G use up to four mobile networks at once; with several SIM cards from different providers, a coverage gap in one network no longer means an outage.
• xDSL and cable: inexpensive, usually already in place and with stable bandwidth. As part of the bundle they provide the base load while mobile absorbs the peaks.
• Starlink: for hard-to-reach regions, construction sites and locations without usable fixed-line service. The satellite link delivers plenty of bandwidth but fluctuates with weather and load; in a bundle the other lines compensate. More on this on our page about Starlink.
• Radio link and fiber: welcome where available. A fiber line in the bundle is not a contradiction but the fastest line with a safety net underneath.

How many lines a router can take depends on the model. A Peplink Balance 20X bonds one fixed-line connection with its built-in LTE modem and suits small sites. The Balance 310X 5G combines fiber or Ethernet, a 5G modem with redundant SIM slots and USB WAN. The Balance SDX Pro bonds up to eight mobile connections alongside 10-gigabit ports in data center or campus use. Which combination makes sense for your site, we calculate in advance rather than promise a figure: the sum of the lines does not arrive one to one because of tunnel overhead and the router's SpeedFusion capacity, but it is clearly more than the fastest single line.

A multi-WAN router on its own can only switch lines or distribute sessions. It can only bond once someone at the other end reassembles the packets. That counterpart is the hub. It sits in a data center with redundant fiber connectivity, not at your site, and is operated by Ascend.

The hub is also the reason the connection has a fixed IP address. Your mobile or DSL lines get changing, often private addresses from the provider. The public address of your virtual leased line, by contrast, sits on the hub and does not change, no matter which line is carrying the traffic. That makes cameras, a server, a phone system or a VPN access reachable from outside, as if the site were on a carrier leased line.

For Peplink routers with SpeedFusion we operate a shared hub, where you pay per active tunnel, or your own hub with a static IPv4 address and port forwarding. For Viprinet routers we provide a Viprinet hub, for Teltonika routers a Bondix hub. You will find details, prices and the choice between shared hub and your own hub on our page about VPN hub hosting. How packet-by-packet bonding works in detail is shown on the page about multi-WAN bonding with Viprinet.

Typical use cases: a branch in a rural area where only narrow DSL is available and the till still has to work. A construction site or outdoor depot that needs internet for two years but cannot get a line. A doctor's practice or care service whose telematics and telephony must not fail. An outside-broadcast van sending live pictures over whatever is currently transmitting; this is how MDR uses bonding for outside broadcasts. And, quite generally, any site waiting for a fiber connection that does not want to stay offline in the meantime. You can find more basics on disruptions and protection on our page about internet outages.

Ascend has been an IT systems house in Nuremberg since 2010 and builds such connections from a single source: we choose router and lines to suit the site, supply the matching SIM cards, preconfigure SpeedFusion, VLANs and firewall, and operate the hub in the data center. After commissioning we monitor lines and tunnel and are reachable around the clock. If you only need the connection for a transitional period, you will also find Peplink routers as rental devices in the Ascend Shop. You can order hardware and plans directly in the Ascend Shop; we take care of the planning.