In the context of network reliability engineering, particularly for a service like NordLayer which functions as a critical path component for secure corporate access, gateway failure represents a single point of failure (SPOF) with significant operational risk. The advertised solution is often an automatic failover or auto-switch configuration. However, from a benchmarking and network performance perspective, the implementation details of this failover are paramount. The term "best way" is not monolithic; it must be evaluated across metrics such as **failover detection time (Td)**, **connection re-establishment time (Tr)**, **session persistence**, and **post-failover performance degradation**.
A naive auto-switch based solely on ICMP ping failure may be insufficient. Consider the following scenarios where a gateway is problematic but not completely dead:
* **High Latency / Packet Loss:** The tunnel is alive but performance is degraded below acceptable thresholds (e.g., >500ms latency, >10% packet loss). A simple ping check might still pass.
* **DNS Failure:** The gateway IP is reachable, but its upstream DNS resolver fails.
* **Partial Route Failure:** The gateway is accessible, but specific destination IP ranges (e.g., a critical SaaS provider's CIDR) are unreachable through it.
Therefore, the "best" method should incorporate a multi-faceted health check. For power users, this often means supplementing NordLayer's native auto-switch with scripting. One could, for instance, use a combination of tools to probe beyond basic connectivity.
```bash
#!/bin/bash
# Example health check logic for gateway 1.2.3.4
TARGET_IP="1.2.3.4"
CRITICAL_HOST="api.internal.company.com"
LATENCY_THRESHOLD=200 # ms
LOSS_THRESHOLD=5 # %
# Measure latency and packet loss
ping_result=$(ping -c 5 -i 0.2 -q "$TARGET_IP" 2>&1 | tail -2)
latency=$(echo "$ping_result" | grep avg | awk -F '/' '{print $5}')
loss=$(echo "$ping_result" | grep loss | awk -F ',' '{print $3}' | awk '{print $1}')
# Check connectivity to a critical service *through* the tunnel
curl_result=$(timeout 3 curl -s -o /dev/null -w "%{http_code}" "https://$CRITICAL_HOST")
# Decision Logic
if (( $(echo "$latency > $LATENCY_THRESHOLD" | bc) )) ||
(( $(echo "$loss > $LOSS_THRESHOLD" | bc) )) ||
[ "$curl_result" != "200" ]; then
echo "FAILURE DETECTED"
# Trigger switch via NordLayer CLI or API if available
fi
```
The core question for the community is: **What is the observed behavioral benchmark of NordLayer's built-in auto-switch during controlled failure conditions?** Specifically:
* What is the **mean time to detect (MTTD)** and **mean time to recover (MTTR)** for a hard gateway shutdown?
* Does the client failover to the next gateway in the list seamlessly, or does it drop all TCP/UDP sessions?
* Are there configurable health check parameters (timeout, interval, failure threshold) in the NordLayer client configuration files?
* How does the performance (throughput, latency) of the secondary gateway compare to the primary in a real-world failover event?
My interest lies in creating a reproducible test bench for this: instrumenting two gateways, introducing controlled failure (iptables drop rules, NIC disablement), and measuring the impact on a sustained WebSocket connection and a series of HTTPS requests. Without concrete data on these parameters, the "auto-switch" feature remains a black box of uncertain reliability. I am seeking reviews that move beyond "it works" or "it failed" and into the quantifiable metrics of the failure mode.
numbers don't lie
numbers don't lie