New voices gather in the Packet Pushers virtual boardroom for a discussion of Cisco’s layer 2 extension technology, Overlay Transport Virtualization (OTV). Ethan Banks hosts a recording of about two hours worth of content about OTV; this show is the second hour (well, almost another hour). Joining Ethan are first-time guests Jamie Caesar, Colby Glass and Ken Matlock. Jamie, Colby and Ken have all done real-world OTV deployments. Among the three, both the Cisco Nexus 7000 platform and ASR1000 platforms are represented.
What’s OTV and why do you care? OTV is a layer 2 extension technology aka data center interconnect (DCI). By L2 extension, we mean extending a VLAN from one data center into a different data center, when those data centers are separated by a layer 3 boundary. OTV is a tunneling overlay that encapsulates Ethernet frames so that they can cross the layer 3 area separating the 2 data centers.
While simple in concept and fairly simple to deploy, OTV is rather complex behind the scenes, which is why this was a nearly 2 hour discussion instead of 20 minute one.
Here in part two, we cover the following high level topics.
- Redundancy of OTV edge devices.
- What is traffic tromboning? How do you minimize it?
- Managing ARP & CAM timeouts to prevent the overlay from becoming a black hole, since OTV doesn’t flood unknown unicasts.
- Coping with MTU sizes and the overhead added by OTV encapsulation.
- Designing your IGP to avoid forming a routing adjacency across the overlay, which would probably result in suboptimal forwarding paths forming.
- Preparing your network to add OTV.
- CLI configuration of OTV.
- Useful OTV “show” commands.
- Our favorite OTV documentation.
Cisco OTV White Papers (excellent resources)
NX-OS and Cisco Nexus Switching: Next-Generation Data Center Architectures (2nd Edition) by Ron Fuller, David Jansen, Matthew McPherson (chapter dedicated to OTV)