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Is bonding the preferred way of implementing ISP redundancy?

In the texts I've seen, bond device has a netmask, gateway of it's own. How can this be obtained if there are two different gateways from two uplinks, which one to choose?

Do I need any special routing rules to go with it or does simply configuring separate interfaces (using Debian, /etc/network/interfaces), i.e eth1, eth2 for their corresponding uplinks and bonding them to bond0 handle routing automatically?

If I want to NAT client machines, do they use bond device's IP as a gateway? Does the bond0 device is the device that goes into iptables nat rules?

Thanks

nik
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Karolis T.
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5 Answers5

14

Bonding is not applicable for this case.

For your solution: You will find some useful notes at Increasing bandwidth with multiple NICs.

For Bonding: You can start at the Wikipedia Link Aggregation and related Channel bonding pages for initial reading on bonding.

Community
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nik
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10

"Bonding" (teaming, trunking, or a host of other terms) NICs is used to increase bandwidth into a switch, or for redundancy for LAN connections.

Redundancy and/or bandwidth expansion for WAN connections (like, to the Internet) is accomplished with routing protocols (typically BGP). Bonding the NICs together on a server computer isn't going to accomplish that.

Evan Anderson
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9

No, you cannot handle multiple ISP uplinks using bonding. Bonding is strictly a Layer 2 (Ethernet) technique, and has no way to detect upstream failures or properly split traffic beyond the direct Ethernet link to your upstream switch/router.

Linux can support multiple upstream ISPs, in either a load-balancing (with limits) or redundant configuration (or both), using policy-based IP routing with multiple routing tables. There is an excellent explanation of the theory and practice, with diagrams, here:

However, I would not recommend implementing that tutorial in a production environment. It's pretty raw, and it will break your existing distribution-specific IP configuration (network-scripts, etc.), and it doesn't handle upstream failures automatically.

The Shorewall project (http://www.shorewall.net/) provides a wrapper mechanism that is far easier and more manageable, especially if you're not already a policy routing pro. It calls itself a "firewall", but it can be strictly useful as a load-balancing, failover-handling gateway to multiple ISPs. The project has a tutorial page that outlines some of the details, here:

Shorewall integrates nicely with the most popular Linux distros, and has actively-maintained packages for RHEL/CentOS, Fedora, Debian, and OpenSUSE.

Specifically, Shorewall provides a set of simplified, rule-based configuration files that you can edit as needed to describe your configuration and implement your desired functionality. It has lots of examples to copy, too.

Ryan B. Lynch
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0

You can bond over multiple ISPs, but there are significant downsides. It involves tunnelling across your existing connections to a single ISP datacentre with a bonding server/cluster. Then you would use this ISPs IP transit to the internet and IP addressing etc.

Your LAN would be presented with a single fully routed IP range, and cope with failures etc, but the downsides are then: You are still relying on a single ISP for the datacentre/IP transit. You are then bonding over the public internet - which means you can't guarantee latency etc, and if you experience problems, it will be much more difficult to sort out.

Normal bonding with a single ISP obviously has its drawbacks, but to me they are outweighed by the quality/support/flexibility issues of doing it with multiple ISPs.

Nic
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you can use DrayTek 2950 http://www.draytek.co.uk/products/vigor2950.html

Plug both your internet lines / connections to it and either run it in load balance mode or failover mode

hope that helps

Mutahir
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