Campaign Monitor Builds Networks with Cumulus Networks Routing on the Host

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Email Marketing & SaaS

Business Objective

Network Simplicity & Reliability


QCT, Ansible

With the desire to manage their switches like servers, Cumulus Linux gave Campaign Monitor freedom, and helped reduced complexity and cost.


Campaign Monitor has redefined how businesses connect with customers. With a simple yet elegant email marketing and automation platform, Campaign Monitor allows businesses to manage email campaigns to reach their target audience and analyze its impact.


Campaign Monitor provides a unique and powerful platform for easily creating email campaigns and, equally important, allows customers to measure campaign impact in real time and react accordingly. To meet their uptime Service Level Agreements (SLAs), Campaign Monitor leverages its own data centers and is constantly working to increase data center reliability economically.

The Campaign Monitor operations team leverages its in-house Linux knowledge and has developed Linux-oriented deployment and monitoring solutions across their entire stack. As part of their service model, Campaign Monitor used an anycast solution for their DNS service.

The Cumulus Networks Routing on the Host solution is the next piece in the Open Networking puzzle. It has empowered Campaign Monitor to greatly improve the availability of critical services across our network. The biggest benefits are the addition of Quagga BGP unnumbered and the elimination of layer 2 technologies such as MLAG, FHRP and STP.

Tynan Young

Sr. Network Engineer at Campaign Monitor


With a strong Linux background and in-house talent, Campaign Monitor evaluated ways to expand Linux across their data centers. With Clos layer 3 architecture, Campaign Monitor decided to deploy Open Networking with Cumulus Linux, a mature native Linux network operating system. Cumulus Linux enabled Campaign Monitor to configure and manage their network switches like servers, treating everything in the data center as just another Linux box.

With Linux across the stack, Campaign Monitor decided to deploy Cumulus Routing on the Host to bring layer 3 benefits all the way down to the host.

The main criteria for selecting Routing on the Host included:

  • Service Reliability: Running a layer 3 routing protocol on the hosts helps Campaign Monitor’s DNS locality and redundancy by using anycast addressing. By advertising the DNS server’s /32 address from the different data centers, the requesting host will reach the closest available DNS server. The anycast solution not only allows for redundancy to the DNS server — as the host can connect to two or more leaf switches, but also redundancy between DNS servers. If the local DNS server becomes unavailable, the route will converge and the local host will have access to the remote DNS server. BGP unnumbered provides all the features required for this solution.
  • BGP Unnumbered: Leveraging BGP unnumbered helps reduce number of IP addresses that are needed to be configured and managed. BGP unnumbered also allows flexibility as IP addresses do not need to be configured on the physical ports — connections and cables can be moved around at will. Automation tools used for other services on the host could also be used for configuring BGP on the host.


Campaign Monitor leveraged Cumulus Networks to deploy an all Linux modern network architecture, capitalizing on their existing in-house Linux expertise and tools. With the desire to manage their switches like servers, Cumulus Linux gave Campaign Monitor freedom, and helped reduced complexity and cost.

With Cumulus Routing on the Host, Campaign Monitor utilized Routing on the Host to greatly simplify DNS, resulting in improved reliability of their critical services across the network.

Combining a Clos layer 3 architecture, Cumulus Linux top of rack switch and Cumulus Routing on the Host empowered Campaign Monitor to eliminate layer 2 complexities like spanning tree and dependency on proprietary protocols like MLAG.

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