Question
What is EFA (Elastic Fabric Adapter)?
Click to reveal answer
Answer
Network device for HPC. Bypasses OS kernel for low-latency, high-throughput communication between instances. Supports MPI/NCCL. Linux only, cluster placement group.
Click to flip back
All Performance & Troubleshooting Flashcards
Q: What is EFA (Elastic Fabric Adapter)?
A: Network device for HPC. Bypasses OS kernel for low-latency, high-throughput communication between instances. Supports MPI/NCCL. Linux only, cluster placement group.
Q: Why might traffic between VPCs over TGW be asymmetric?
A: TGW sends traffic to any AZ in the destination VPC. Return path may use a different AZ. Enable appliance mode for stateful inspection to fix this.
Q: What is the MTU for traffic over VPN?
A: 1500 bytes maximum due to IPSec encapsulation overhead. Cannot use jumbo frames (9001 MTU) over VPN tunnels.
Q: What is the per-tunnel throughput for Site-to-Site VPN?
A: 1.25 Gbps per tunnel. Use ECMP over Transit Gateway (multiple VPN connections) to aggregate bandwidth beyond single tunnel limit.
Q: What causes a blackhole route in Transit Gateway?
A: Attachment is deleted but route remains, or static route points to non-existent attachment. Traffic is silently dropped. Check TGW route table for blackhole status.
Q: How do you troubleshoot Direct Connect connectivity?
A: Check: physical layer (light levels, CRC errors) → BGP session (state, prefixes) → route propagation → security groups/NACLs → VIF state in console.
Q: What is Reachability Analyzer?
A: Automated tool that tests connectivity between two points in your VPC network. Analyzes route tables, SGs, NACLs, and identifies the component blocking traffic.
Q: What is the bandwidth of a NAT Gateway?
A: 100 Gbps burst. If you need more, split resources across multiple subnets with separate NAT Gateways. 55,000 simultaneous connections per destination.
Q: How does cross-region VPC peering affect performance?
A: Traffic is encrypted, uses AWS backbone (not internet). Latency depends on geographic distance. No single point of bandwidth limit published. Billed per GB.
Q: What is Network Access Analyzer?
A: Identifies unintended network access by analyzing security groups, NACLs, route tables, and network paths against access requirements you define.