When deploying network monitoring at enterprise scale (5,000+ devices), SNMP trap handling becomes critical infrastructure. The core requirements break down into:

• Single entry point for all network devices (HA preferred)
• Dynamic routing based on source IP ranges
• UDP-specific load distribution capabilities
• Optional packet mirroring for secondary processing

Through testing several approaches, here's what we found:

Option 1: iptables DNAT Routing

Our current production implementation uses Linux netfilter rules:

# Site ABC devices → Processing server 10.1.2.3
iptables -t nat -A PREROUTING -p udp --dport 162 \
    -s 10.0.0.0/19 -j DNAT --to-destination 10.1.2.3

# Enable packet mirroring (requires tee module)
iptables -t mangle -A PREROUTING -p udp --dport 162 \
    -s 10.0.33.0/21 -j TEE --gateway 10.1.2.4

Pros: Near-line-rate performance (handles 50k+ traps/sec on modest hardware)
Cons: Limited to L3/L4 filtering, no application-layer inspection

Option 2: Custom snmptrapd Handler

A Python-based alternative for deeper inspection:

import subprocess
from pysnmp.hlapi import *

def cbFun(snmpEngine, stateReference, contextEngineId, contextName,
          varBinds, cbCtx):
    src_ip = snmpEngine.msgAndPduDsp.getTransportInfo(stateReference)[0]
    
    if src_ip.startswith('10.0.'):
        subprocess.run(['snmptrap', '-v2c', '-cpublic',
                       '10.1.2.3', '1.3.6.1.4.1.0', *varBinds])
    elif src_ip.startswith('10.1.'):
        # Mirror to two destinations
        subprocess.run(['snmptrap', ...], check=False)
        subprocess.run(['snmptrap', ...], check=False)

For complex deployments, consider these specialized solutions:

HAProxy UDP Configuration

frontend snmp_traps
    bind :162
    mode udp
    default_backend trap_processors

backend trap_processors
    mode udp
    balance source
    server s1 10.1.2.3:162 check
    server s2 10.3.2.1:162 check

Note: Requires HAProxy 2.0+ for full UDP support

Commercial Load Balancers

F5 BIG-IP configurations should include:

• UDP profile with SNMP protocol support
• Persistence based on source IP
• iRule scripting for advanced routing logic

For most large deployments, we recommend a hybrid approach:

1. Use iptables for initial fan-out to regional collectors
2. Implement HAProxy for final distribution to processing nodes
3. Consider Kafka or RabbitMQ for durable queueing when processing requires persistence

Performance metrics from our 5k-device deployment:

When dealing with 5000+ network devices, traditional SNMP trap handling approaches quickly become bottlenecks. The fundamental requirements break down into:

• Centralized trap collection point with HA capability
• Intelligent routing based on source IP/subnet
• Horizontal scaling for back-end processing
• Optional packet duplication for analytics/mirroring

Let's examine the technical trade-offs of each approach you've considered:

// IPTables DNAT Example (tested solution)
iptables -t nat -A PREROUTING -p udp --dport 162 \
  -s 10.0.0.0/19 -j DNAT --to-destination 10.1.2.3

Pros: Kernel-level performance, minimal latency
Cons: Limited to L3/L4 filtering, no payload inspection

For maximal flexibility, consider a custom router using Go's concurrency primitives:

package main

import (
    "log"
    "net"
    "sync"
)

func forward(src net.Conn, dest string, wg *sync.WaitGroup) {
    defer wg.Done()
    dst, _ := net.Dial("udp", dest)
    buf := make([]byte, 65507)
    
    for {
        n, _ := src.Read(buf)
        // Add source-based routing logic here
        if shouldMirror(src.RemoteAddr()) {
            go mirrorPacket(buf[:n])
        }
        dst.Write(buf[:n])
    }
}

func main() {
    ln, _ := net.ListenPacket("udp", ":162")
    var wg sync.WaitGroup
    
    wg.Add(1)
    go forward(ln, "10.1.2.3:162", &wg)
    wg.Wait()
}

For your scale, I recommend this hybrid approach:

1. Frontend: Keepalived + IPTables DNAT (for raw throughput)
2. Middleware: Custom Go router (for complex routing rules)
3. Backend: Kafka queue (for decoupling processors)

# Keepalived config snippet
virtual_server 10.0.0.10 162 {
    protocol UDP
    real_server 10.1.2.3 162 {
        weight 1
    }
}