Show 252 – Design & Build 5 – BGP In The Data Center

To the average enterprise network engineer, BGP is found in the data center at the edge. You use it to connect to the WAN, or to exchange routes with another network you might need to peer with. By and large, BGP is more about the WAN, service providers, and the Internet. It’s much less about programming forwarding tables to route traffic around your data center.

And yet, BGP keeps popping up in SDN conversations. For data centers of a certain size, maybe BGP makes sense.

To find out when and if it does, we gathered four engineers from various parts of the world to discuss data center BGP on this 5th installment of the Design & Build series.

Our guests include Eric Leahy, a network engineer and designer who specializes LAN switching for data center and campus; Jason Gooley, who works at a large network vendor; Daniel Hertzberg, an infrastructure engineer at a financial services company; and Justin Seabrook-Rocha, a network engineer and architect for a large U.S. colo provider.

Show Notes:

1. Level Setting

• What is BGP and how is it different from an IGP such as OSPF?
• Traditionally, why haven’t we used BGP as an IGP?
• What else is BGP good for?

2. What Scenarios Make Sense for BGP in the Data Center?

• Size, desire to zone
• Policy control of routes in and out of ASNs (zones or tiers)
• Control plane function – carry information beyond routes
• Conversely, are there scenarios where BGP doesn’t make sense?

3. Design Principles

• Do we need a specific physical topology for BGP to make sense?
• Where to eBGP, where to iBGP?
• Where do we summarize routes, or do we?
• Are route-reflectors useful in BGP DC design?
• Are memory or CPU unusual concerns when spinning up the BGP process?

4. Implementation Details

• Timer tuning can be a big deal in IGPs. What about BGP?
• BGP traditionally doesn’t like ECMP, a key DC element. How do we bring ECMP to life in a BGP-based DC?
• How well do cross-vendor BGP peerings do (i.e. Cisco to Dell)? Any interoperability concerns to be aware of?

5. War Stories, Takeaways, Parting Thoughts

If you want to get more information on BGP, one resource is a Packet Pushers podcast with Cisco on BGP and VXLAN.