Anycast Resources

Anycast is a design in which a single destination IP address is shared by devices in multiple locations. It can be used to implement large-scale UDP services (example: DNS) or to build multi-site high-availability solutions without DNS-based load balancing.

Anycast is also commonly used in data center fabrics to implement redundant first-hop gateways, and with overlay virtual networks (example: VXLAN) to build scale-out gateway clusters or MLAG clusters.

What Is Anycast?

• Overview
• Anycast Fundamentals
• Local TCP Anycast Is Really Hard
• Chasing Anycast IP Addresses

Want to use anycast in a public cloud? Become a Cloudflare user ;) or use AWS Global Accelerator (described in Amazon Web Services Networking webinar).

Anycast in Data Center Fabrics

• Optimal L3 Forwarding with VARP and Active/Active VRRP
• VRRP, Anycasts, Fabrics and Optimal Forwarding
• Arista EOS Virtual ARP (VARP) Behind the Scenes
• Duplicate ARP Replies with Anycast Gateways
• Combining MLAG Clusters with VXLAN Fabric
• Using EVPN/VXLAN with MLAG Clusters

For more information watch:

• Mixed Layer-2 + Layer-3 Fabrics in Leaf-and-Spine Fabric Architectures webinar
• Routing with EVPN in EVPN Technical Deep Dive
• Arista EOS part of Data Center Fabric Architectures webinar.

Network Designs Using Anycast

• Ingress Traffic Flow in Multi-Data Center Deployments
• Routing in Stretched VLAN Designs
• IRB Design Models Overview
• Routing at the Outer Edge of the Fabric

Anycast Use Cases

• Dynamic Routing with Virtual Appliances
• Virtual Appliance Routing – Network Engineer’s Survival Guide
• Where Would You Need DNS Anycast?

Anycast Multipathing

• Weird: Wrong Subnet Mask Causing Unicast Flooding
• Single-Metric Unequal-Cost Multipathing Is Hard

Testing IP Anycast in a Virtual Lab

• Anycast Works Just Fine with MPLS/LDP
• Building a BGP Anycast Lab
• IRB with Anycast Gateways

Further Reading

• Anycast DNS in Enterprise Networks
• Egress Anycast in Cloudflare Network