AKS Networking and Ingress#

AKS networking involves three layers: how pods communicate (CNI plugin), how traffic enters the cluster (load balancers and ingress controllers), and how the cluster connects to other Azure resources (VNet integration, private endpoints). Each layer has Azure-specific behavior that differs from generic Kubernetes.

Azure Load Balancer for Services#

When you create a Service of type LoadBalancer in AKS, Azure provisions a Standard SKU Azure Load Balancer. AKS manages the load balancer rules and health probes automatically.

Configuration File Structure#

HAProxy uses a single configuration file, typically /etc/haproxy/haproxy.cfg. The configuration is divided into four sections: global (process-level settings), defaults (default values for all proxies), frontend (client-facing listeners), and backend (server pools).

global
    log /dev/log local0
    log /dev/log local1 notice
    maxconn 50000
    user haproxy
    group haproxy
    daemon
    stats socket /run/haproxy/admin.sock mode 660 level admin
    tune.ssl.default-dh-param 2048

defaults
    log     global
    mode    http
    option  httplog
    option  dontlognull
    timeout connect 5s
    timeout client  30s
    timeout server  30s
    timeout http-request 10s
    timeout http-keep-alive 10s
    errorfile 400 /etc/haproxy/errors/400.http
    errorfile 403 /etc/haproxy/errors/403.http
    errorfile 500 /etc/haproxy/errors/500.http
    errorfile 502 /etc/haproxy/errors/502.http
    errorfile 503 /etc/haproxy/errors/503.http

The maxconn in the global section sets the hard limit on total simultaneous connections. The timeout values in defaults apply to all frontends and backends unless overridden. The stats socket directive enables the runtime API, which is essential for operational management.

L4 vs L7 Load Balancing#

The distinction between Layer 4 and Layer 7 load balancing determines what the load balancer can see and what routing decisions it can make.

Layer 4 (Transport) load balancers work at the TCP/UDP level. They see source/destination IPs and ports but not the content of the traffic. They forward raw TCP connections to backends. This makes them fast (no protocol parsing), protocol-agnostic (works for HTTP, gRPC, database connections, custom protocols), and transparent (the backend sees the original packets, mostly). Use L4 for database connections, raw TCP services, and when you need maximum throughput with minimum latency.