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Thomas Mangin edited this page Nov 13, 2025 · 11 revisions

DDoS Mitigation with ExaBGP

Automated DDoS protection using BGP FlowSpec

🛡️ ExaBGP pioneered open-source FlowSpec - enabling network-wide DDoS mitigation in seconds

Table of Contents

Overview

DDoS mitigation with ExaBGP enables automated, network-wide traffic filtering using BGP FlowSpec.

The Problem

Traditional DDoS response is slow:

  1. ⏱️ Detection: Minutes to identify attack
  2. 🔧 Manual intervention: SSH to routers, configure ACLs
  3. 📝 Error-prone: Manual configuration mistakes
  4. 🐌 Slow deployment: Can't update hundreds of routers quickly
  5. 💰 Damage: Attack causes disruption before mitigation

The ExaBGP Solution

Automated FlowSpec-based mitigation:

  1. ⚡ Instant detection: Automated systems detect attack patterns
  2. 🤖 Automated response: ExaBGP generates FlowSpec rules via API
  3. 🌐 Network-wide: Rules propagate to all edge routers via BGP
  4. 🚀 Fast: Attack blocked in seconds (not minutes)
  5. ✅ Reliable: No manual intervention required

Why FlowSpec for DDoS Mitigation?

Advantages Over Traditional Methods

vs. RTBH (Remote Triggered Black Hole):

  • ✅ Granular filtering: Match on ports, protocols, packet size, TCP flags
  • ✅ Surgical mitigation: Rate-limit instead of complete blackhole
  • ✅ Reduced collateral damage: Single rule vs. thousands of /32 prefixes
  • ✅ Flexible actions: Discard, rate-limit, redirect, or mark traffic

vs. On-Premises Scrubbing:

  • ✅ Upstream filtering: Traffic blocked at provider edge (before reaching your network)
  • ✅ Bandwidth savings: Attack traffic never consumes your bandwidth
  • ✅ Scalability: Leverage provider infrastructure
  • ✅ Fast convergence: BGP propagation in seconds

vs. Cloud Scrubbing Services:

  • ✅ No third-party dependency: On-premises control
  • ✅ Lower cost: No per-GB scrubbing fees
  • ✅ Lower latency: No traffic redirection
  • ✅ Privacy: Traffic stays in your network

Architecture Patterns

Pattern 1: Centralized FlowSpec Controller

Most common deployment:

┌─────────────────────┐
│  DDoS Detection     │  FastNetMon, custom detection
│  System             │
└──────────┬──────────┘
           │ Attack detected
           ▼
┌─────────────────────┐
│  ExaBGP             │  FlowSpec controller
│  (Central)          │  Generates rules via API
└──────────┬──────────┘
           │ BGP FlowSpec UPDATE
           ▼
┌─────────────────────┐
│  Edge Routers       │  Cisco, Juniper, Arista, etc.
│  (100s-1000s)       │  Apply filters in hardware
└──────────┬──────────┘
           │ Filtered traffic
           ▼
     Attack blocked ✅

Characteristics:

  • Single ExaBGP instance as FlowSpec controller
  • Peers with route reflectors or edge routers
  • Rules propagate network-wide via BGP
  • Centralized logging and management

Pattern 2: Distributed FlowSpec with Route Reflectors

For large-scale networks:

┌────────────────┐         ┌────────────────┐
│ ExaBGP         │◄───────►│ Route          │
│ FlowSpec       │   iBGP  │ Reflectors     │
│ Controller     │         │                │
└────────────────┘         └────────┬───────┘
                                    │
                    ┌───────────────┼───────────────┐
                    ▼               ▼               ▼
            ┌──────────────┐ ┌──────────────┐ ┌──────────────┐
            │ Edge Router  │ │ Edge Router  │ │ Edge Router  │
            │ (Region A)   │ │ (Region B)   │ │ (Region C)   │
            └──────────────┘ └──────────────┘ └──────────────┘

Benefits:

  • Scalable to thousands of edge routers
  • Reduced BGP session overhead
  • Regional route reflectors for redundancy
  • Standard BGP topology

Pattern 3: Hybrid (FlowSpec + Scrubbing)

Combine FlowSpec with scrubbing centers:

┌─────────────────┐
│ Detection       │
└────────┬────────┘
         │
         ▼
┌─────────────────┐
│ ExaBGP          │
│ Decision Logic  │
└────────┬────────┘
         │
    ┌────┴──────────┐
    ▼               ▼
Small Attack    Large Attack
(< 1 Gbps)     (> 1 Gbps)
    │               │
    ▼               ▼
FlowSpec        FlowSpec
discard         redirect to VRF
                    │
                    ▼
             ┌──────────────┐
             │ Scrubbing    │
             │ Center       │
             └──────┬───────┘
                    │
                    ▼
             Clean traffic back

Use cases:

  • Small attacks: Block at edge with FlowSpec
  • Large volumetric attacks: Redirect to scrubbing
  • Graduated response based on attack size

Detection Integration

ExaBGP can integrate with various DDoS detection systems:

Open-Source Options:

  • FastNetMon Community - High-performance DDoS detection (native ExaBGP support)
  • Custom detection - Build your own using flow analysis tools

Turnkey Commercial DDoS Solutions:

  • FastNetMon Advanced - Enterprise DDoS detection and mitigation platform
  • Wanguard by Andrisoft - Complete DDoS protection solution with ExaBGP integration via BGP Connector

💡 Note: Both turnkey solutions offer comprehensive DDoS protection with management interfaces, reporting, and automated mitigation workflows. Wanguard integrates with ExaBGP through its BGP Connector component, supporting RTBH, FlowSpec, and traffic scrubbing.

Flow Analysis Tools (for custom detection):

  • Akvorado - Flow collector and visualizer (can feed custom detection logic)
  • pmacct - Flow accounting and analysis
  • nfdump/nfsen - NetFlow analysis toolkit

Option 1: FastNetMon Community

FastNetMon Community is an open-source DDoS detection system with native ExaBGP integration.

Architecture

FastNetMon → sFlow/NetFlow → Analysis → ExaBGP API → FlowSpec

Configuration

FastNetMon config (/etc/fastnetmon.conf):

# Enable ExaBGP integration
enable_ban_for_tcp_syn_flood = on
enable_ban_for_udp_flood = on
enable_ban_for_icmp_flood = on

# ExaBGP FlowSpec
exabgp = on
exabgp_flow_spec_announces = on
exabgp_command_pipe = /var/run/exabgp.cmd

# Thresholds
ban_for_pps = on
threshold_pps = 20000
ban_for_bandwidth = on
threshold_mbps = 1000

ExaBGP config (/etc/exabgp/exabgp.conf):

neighbor 192.168.1.1 {
    router-id 192.168.1.2;
    local-address 192.168.1.2;
    local-as 65001;
    peer-as 65000;

    family {
        ipv4 flowspec;
    }

    api {
        processes [ fastnetmon ];
    }
}

process fastnetmon {
    run /etc/exabgp/api/fastnetmon.py;
    encoder text;
}

Integration script (/etc/exabgp/api/fastnetmon.py):

#!/usr/bin/env python3
"""
FastNetMon integration for ExaBGP FlowSpec
Reads attack notifications and generates FlowSpec rules
"""
import sys
import time
import os

# Named pipe from FastNetMon
PIPE_PATH = "/var/run/exabgp.cmd"

def read_fastnetmon_commands():
    """Read FlowSpec commands from FastNetMon pipe"""
    if not os.path.exists(PIPE_PATH):
        os.mkfifo(PIPE_PATH)

    while True:
        with open(PIPE_PATH, 'r') as pipe:
            for line in pipe:
                command = line.strip()
                if command:
                    # Forward to ExaBGP
                    sys.stdout.write(command + "\n")
                    sys.stdout.flush()
                    sys.stderr.write(f"[FASTNETMON] {command}\n")

time.sleep(2)
read_fastnetmon_commands()

Option 3: Custom Detection

Build your own detection system:

#!/usr/bin/env python3
"""
Custom DDoS detection and mitigation
Analyzes traffic patterns and generates FlowSpec rules
"""
import sys
import time
import collections
from datetime import datetime

# Attack detection state
traffic_stats = collections.defaultdict(lambda: {'pps': 0, 'bps': 0})
blocked_sources = set()

# Thresholds
SYN_FLOOD_THRESHOLD = 10000  # SYN packets per second
UDP_FLOOD_THRESHOLD = 50000  # UDP packets per second
BANDWIDTH_THRESHOLD = 1000000000  # 1 Gbps

def analyze_traffic():
    """
    Analyze traffic patterns (placeholder - integrate with your monitoring)
    Returns: list of detected attacks
    """
    # TODO: Integrate with your traffic analysis system
    # Examples: sFlow collector, SNMP polling, pcap analysis

    attacks = []

    for source_ip, stats in traffic_stats.items():
        # SYN flood detection
        if stats['syn_pps'] > SYN_FLOOD_THRESHOLD:
            attacks.append({
                'type': 'syn_flood',
                'source': source_ip,
                'metric': stats['syn_pps'],
                'dest_port': stats.get('dest_port', 80)
            })

        # UDP flood detection
        if stats['udp_pps'] > UDP_FLOOD_THRESHOLD:
            attacks.append({
                'type': 'udp_flood',
                'source': source_ip,
                'metric': stats['udp_pps']
            })

        # Bandwidth-based detection
        if stats['bps'] > BANDWIDTH_THRESHOLD:
            attacks.append({
                'type': 'bandwidth_flood',
                'source': source_ip,
                'metric': stats['bps']
            })

    return attacks

def mitigate_attack(attack):
    """Generate and announce FlowSpec rule"""
    attack_type = attack['type']
    source = attack['source']

    if source in blocked_sources:
        return  # Already blocked

    if attack_type == 'syn_flood':
        dest_port = attack.get('dest_port', 80)
        rule = (
            f"announce flow route {{ "
            f"match {{ source {source}/32; destination-port ={dest_port}; "
            f"protocol =tcp; tcp-flags [ syn ]; }} "
            f"then {{ rate-limit 10000000; }} "
            f"}}"
        )

    elif attack_type == 'udp_flood':
        rule = (
            f"announce flow route {{ "
            f"match {{ source {source}/32; protocol =udp; }} "
            f"then {{ rate-limit 5000000; }} "
            f"}}"
        )

    elif attack_type == 'bandwidth_flood':
        rule = (
            f"announce flow route {{ "
            f"match {{ source {source}/32; }} "
            f"then {{ rate-limit 1000000; }} "
            f"}}"
        )

    else:
        rule = (
            f"announce flow route {{ "
            f"match {{ source {source}/32; }} "
            f"then {{ discard; }} "
            f"}}"
        )

    sys.stdout.write(rule + "\n")
    sys.stdout.flush()

    blocked_sources.add(source)

    timestamp = datetime.now().strftime('%Y-%m-%d %H:%M:%S')
    sys.stderr.write(
        f"[{timestamp}] Blocked {attack_type} from {source} "
        f"(metric: {attack['metric']})\n"
    )

    # Schedule auto-withdrawal after 300 seconds
    schedule_withdrawal(rule, 300)

def schedule_withdrawal(rule, timeout):
    """Auto-withdraw rule after timeout"""
    import threading

    def withdraw_after_timeout():
        time.sleep(timeout)
        withdraw = rule.replace('announce', 'withdraw')
        # Remove 'then' clause for withdrawal
        withdraw = withdraw.split('then')[0].rstrip() + '}'
        sys.stdout.write(withdraw + "\n")
        sys.stdout.flush()
        sys.stderr.write(f"[AUTO-WITHDRAW] {withdraw}\n")

    thread = threading.Thread(target=withdraw_after_timeout, daemon=True)
    thread.start()

# Main detection loop
time.sleep(2)

sys.stderr.write("[DETECTION] Custom DDoS detection started\n")

while True:
    attacks = analyze_traffic()

    for attack in attacks:
        mitigate_attack(attack)

    time.sleep(5)  # Check every 5 seconds

Option 2: Wanguard Integration

Wanguard by Andrisoft offers turnkey DDoS protection with ExaBGP integration via its BGP Connector component.

Architecture

Wanguard Detection → Response System → BGP Connector → ExaBGP → Edge Routers

Key Features

BGP Connector supports:

  • Remote Triggered Black Hole (RTBH) - Null-route attacked destinations
  • BGP FlowSpec - Granular traffic filtering at edge routers
  • Traffic Scrubbing - Redirect traffic to cleaning servers
  • Source RTBH - Block attacking source IPs
  • Automated & Manual Control - REST API, console, or anomaly-triggered

Configuration

For complete setup instructions, refer to the official Andrisoft documentation:

Wanguard BGP Connector Configuration Guide

The guide covers:

  • Installing and configuring ExaBGP
  • Setting up the Wanguard BGP Connector component
  • Configuring pipe file paths and permissions
  • Connector role selection (Mitigation or Diversion)
  • Enabling BGP FlowSpec support
  • Community and prefix restrictions
  • Integration with Wanguard Response System

How It Works

Once configured, Wanguard's detection engine automatically triggers BGP announcements via ExaBGP:

  1. Attack Detection - Wanguard identifies DDoS attack patterns
  2. Response Trigger - Response system activates mitigation
  3. BGP Announcement - Writes FlowSpec/RTBH rules to ExaBGP pipe
  4. Network-Wide Mitigation - ExaBGP propagates rules to edge routers

Mitigation can also be triggered manually via Wanguard's REST API or console interface.

Additional Resources

Complete Workflow

End-to-End DDoS Mitigation

Step 1: Detection

Attack traffic → Edge routers → NetFlow/sFlow → Detection system

Detection triggers when:

  • Packets per second > threshold
  • Bandwidth > threshold
  • Anomaly detected by ML model
  • Specific attack patterns identified

Step 2: Rule Generation

# Detection system generates FlowSpec rule
rule = (
    "announce flow route { "
    "match { source 203.0.113.0/24; destination-port =80; protocol =tcp; } "
    "then { discard; } "
    "}"
)

Step 3: ExaBGP Announcement

# Send to ExaBGP via API
sys.stdout.write(rule + "\n")
sys.stdout.flush()

Step 4: BGP Propagation

ExaBGP → BGP UPDATE (FlowSpec) → Route Reflectors → Edge Routers

Convergence time: 1-5 seconds network-wide

Step 5: Traffic Filtering

Edge routers install FlowSpec rule in hardware (TCAM)
→ Matching traffic dropped/rate-limited at wire speed
→ Attack blocked ✅

Step 6: Auto-Withdrawal

# After attack ends (e.g., 5 minutes)
time.sleep(300)
withdraw = "withdraw flow route { match { source 203.0.113.0/24; ... } }"
sys.stdout.write(withdraw + "\n")
sys.stdout.flush()

Attack Types and Mitigation

1. SYN Flood

Attack: TCP SYN packets without completing handshake

Detection:

  • High SYN rate to specific port
  • SYN packets without corresponding ACK

Mitigation:

announce flow route {
    match {
        destination 100.10.0.100/32;  # Target server
        destination-port =80|=443;     # HTTP/HTTPS
        protocol =tcp;
        tcp-flags [ syn ];             # SYN flag only
    }
    then {
        rate-limit 10000000;           # 10 Mbps
    }
}

2. UDP Amplification

Attack: Spoofed UDP requests to amplification servers (DNS, NTP, SSDP, etc.)

Detection:

  • Large UDP responses (> 512 bytes)
  • High volume from specific source ports (53, 123, 1900)

Mitigation:

# DNS amplification
announce flow route {
    match {
        source-port =53;               # DNS responses
        protocol =udp;
        packet-length >512;            # Large responses
    }
    then {
        discard;
    }
}

# NTP amplification
announce flow route {
    match {
        source-port =123;              # NTP responses
        protocol =udp;
        packet-length >100;
    }
    then {
        discard;
    }
}

# SSDP amplification
announce flow route {
    match {
        source-port =1900;             # SSDP
        protocol =udp;
    }
    then {
        discard;
    }
}

3. HTTP Flood

Attack: High volume of HTTP requests

Detection:

  • High connection rate to web servers
  • Unusual HTTP request patterns

Mitigation:

# Rate-limit HTTP traffic from attack source
announce flow route {
    match {
        source 10.0.0.0/8;             # Attack network
        destination-port =80|=443;
        protocol =tcp;
    }
    then {
        rate-limit 5000000;            # 5 MB/sec (bytes/sec, RFC 5575)
    }
}

4. ICMP Flood

Attack: High volume of ICMP packets (ping flood, smurf attack)

Detection:

  • High ICMP packet rate
  • Large ICMP packet sizes

Mitigation:

# Block all ICMP during attack
announce flow route {
    match {
        protocol =icmp;
    }
    then {
        discard;
    }
}

# Or rate-limit ICMP
announce flow route {
    match {
        protocol =icmp;
        icmp-type =8;                  # Echo request
    }
    then {
        rate-limit 1000000;            # 1 Mbps
    }
}

5. Fragmentation Attack

Attack: Malformed or excessive fragmented packets

Detection:

  • High rate of fragmented packets
  • Invalid fragment patterns

Mitigation:

# Block all fragmented packets
announce flow route {
    match {
        fragment [ is-fragment ];
    }
    then {
        discard;
    }
}

6. Volumetric Attack

Attack: High bandwidth consumption (> line capacity)

Detection:

  • Total bandwidth exceeds threshold
  • Traffic from specific sources/networks

Mitigation:

# Aggressive rate-limiting for attack sources
announce flow route {
    match {
        source 203.0.113.0/24;
    }
    then {
        rate-limit 1000000;            # 1 Mbps total
    }
}

# Or redirect to scrubbing VRF
announce flow route {
    match {
        destination 100.10.0.0/24;     # Attacked network
    }
    then {
        redirect 65001:999;            # Scrubbing VRF
    }
}

Implementation Guide

Step 1: Install ExaBGP

# Using pip
pip3 install exabgp

# Verify installation
exabgp --version

See Installation Guide for details.

Step 2: Configure ExaBGP

Create config (/etc/exabgp/ddos-mitigation.conf):

neighbor 192.168.1.1 {
    router-id 192.168.1.2;
    local-address 192.168.1.2;
    local-as 65001;
    peer-as 65000;

    family {
        ipv4 flowspec;
    }

    api {
        processes [ ddos-controller ];
    }
}

process ddos-controller {
    run /etc/exabgp/api/ddos_controller.py;
    encoder text;
}

Step 3: Create Detection Script

Basic template (/etc/exabgp/api/ddos_controller.py):

#!/usr/bin/env python3
import sys
import time

time.sleep(2)
sys.stderr.write("[DDOS] Controller started\n")

# Your detection logic here
# When attack detected, generate FlowSpec rule:

def block_attack(source_ip, attack_type):
    rule = (
        f"announce flow route {{ "
        f"match {{ source {source_ip}/32; }} "
        f"then {{ discard; }} "
        f"}}"
    )
    sys.stdout.write(rule + "\n")
    sys.stdout.flush()
    sys.stderr.write(f"[DDOS] Blocked {attack_type} from {source_ip}\n")

# Main loop
while True:
    # TODO: Integrate with your detection system
    time.sleep(10)

Step 4: Configure Edge Routers

Cisco IOS-XR:

router bgp 65000
 neighbor 192.168.1.2 remote-as 65001
 !
 address-family ipv4 flowspec
  neighbor 192.168.1.2 activate
 !
!
flowspec
 local-install interface-all
!

Juniper Junos:

protocols {
    bgp {
        group exabgp {
            type external;
            peer-as 65001;
            neighbor 192.168.1.2 {
                family inet {
                    flow;
                }
            }
        }
    }
}

routing-options {
    flow {
        validation {
            local {
                enabled;
            }
        }
    }
}

Step 5: Test FlowSpec Rules

Manual test:

# Start ExaBGP
exabgp /etc/exabgp/ddos-mitigation.conf

# In another terminal, inject test rule
echo "announce flow route { match { source 10.0.0.1/32; } then { discard; } }" > /tmp/exabgp.cmd

Verify on router:

# Cisco
show flowspec ipv4 summary
show flowspec ipv4 detail

# Juniper
show firewall filter __flowspec_default_inet__

Production Deployment

High Availability

Deploy redundant ExaBGP instances:

┌────────────────┐         ┌────────────────┐
│ ExaBGP         │         │ ExaBGP         │
│ Primary        │         │ Secondary      │
│ 192.168.1.2    │         │ 192.168.1.3    │
└────────┬───────┘         └───────┬────────┘
         │                         │
         └────────────┬────────────┘
                      │
                      ▼
              ┌───────────────┐
              │ Route         │
              │ Reflectors    │
              └───────────────┘

Both instances:

  • Run same detection logic
  • Announce same FlowSpec rules
  • BGP handles deduplication

Logging and Auditing

Log all FlowSpec announcements:

import logging

logging.basicConfig(
    filename='/var/log/exabgp-ddos.log',
    level=logging.INFO,
    format='%(asctime)s [%(levelname)s] %(message)s'
)

def announce_flowspec(rule, reason):
    sys.stdout.write(rule + "\n")
    sys.stdout.flush()
    logging.info(f"ANNOUNCE: {rule} - Reason: {reason}")

Alerting Integration

Send alerts to NOC:

import requests

def send_alert(message, severity='high'):
    """Send alert to Slack/PagerDuty/email"""
    # Slack webhook
    requests.post(
        "https://hooks.slack.com/services/YOUR/WEBHOOK/URL",
        json={
            "text": f":warning: DDoS Alert: {message}",
            "username": "ExaBGP DDoS Controller"
        }
    )

    # PagerDuty
    requests.post(
        "https://events.pagerduty.com/v2/enqueue",
        json={
            "routing_key": "YOUR_ROUTING_KEY",
            "event_action": "trigger",
            "payload": {
                "summary": message,
                "severity": severity,
                "source": "ExaBGP"
            }
        }
    )

# When blocking attack
send_alert(f"Blocking SYN flood from {source_ip} to port {port}")

Monitoring and Alerting

Metrics to Track

1. Attack Metrics:

  • Number of active FlowSpec rules
  • Attacks detected per hour
  • Attack types distribution
  • Top attack sources

2. Mitigation Metrics:

  • Time to mitigation (detection → blocking)
  • Bandwidth saved
  • False positive rate
  • Rule withdrawal time

3. System Metrics:

  • ExaBGP process health
  • BGP session state
  • API response time
  • Rule announcement latency

Monitoring Script

#!/usr/bin/env python3
"""
Monitor ExaBGP DDoS mitigation metrics
"""
import time
import subprocess
import requests

# Metrics
active_rules = 0
attacks_detected = 0
attacks_blocked = 0

def check_exabgp_health():
    """Check if ExaBGP process is running"""
    try:
        result = subprocess.run(
            ['pgrep', '-f', 'exabgp'],
            capture_output=True,
            timeout=5
        )
        return result.returncode == 0
    except:
        return False

def check_bgp_session():
    """Check BGP session state (example for Cisco via SNMP)"""
    # TODO: Implement SNMP check or router API
    pass

def export_metrics_to_prometheus():
    """Export metrics to Prometheus"""
    # Expose metrics endpoint
    metrics = f"""
# HELP exabgp_ddos_active_rules Number of active FlowSpec rules
# TYPE exabgp_ddos_active_rules gauge
exabgp_ddos_active_rules {active_rules}

# HELP exabgp_ddos_attacks_detected Total attacks detected
# TYPE exabgp_ddos_attacks_detected counter
exabgp_ddos_attacks_detected {attacks_detected}

# HELP exabgp_ddos_attacks_blocked Total attacks blocked
# TYPE exabgp_ddos_attacks_blocked counter
exabgp_ddos_attacks_blocked {attacks_blocked}
"""
    # Write to textfile collector or push to Pushgateway
    with open('/var/lib/prometheus/node-exporter/exabgp_ddos.prom', 'w') as f:
        f.write(metrics)

while True:
    if not check_exabgp_health():
        send_alert("ExaBGP process not running!", severity='critical')

    export_metrics_to_prometheus()
    time.sleep(60)

Best Practices

1. Graduated Response

Start conservative, escalate if needed:

# Level 1: Rate-limit (warning)
rate_limit_1 = 50000000  # 50 Mbps

# Level 2: Tighter rate-limit
rate_limit_2 = 10000000  # 10 Mbps

# Level 3: Very tight rate-limit
rate_limit_3 = 1000000   # 1 Mbps

# Level 4: Block completely
# discard

2. Whitelist Critical Services

Never block critical infrastructure:

WHITELIST = [
    '8.8.8.8',      # Google DNS
    '1.1.1.1',      # Cloudflare DNS
    # Add your critical IPs
]

def should_block(ip):
    return ip not in WHITELIST

3. Auto-Expiration

Always set TTL on rules:

def announce_with_ttl(rule, ttl=300):
    """Announce rule with auto-withdrawal"""
    sys.stdout.write(rule + "\n")
    sys.stdout.flush()

    # Schedule withdrawal
    threading.Timer(ttl, withdraw_rule, args=[rule]).start()

4. Rate-Limit Before Blocking

Try rate-limiting first:

if attack_severity < 5:
    action = f"rate-limit {bandwidth}"
else:
    action = "discard"

5. Validate Rules Before Announcement

Prevent misconfigurations:

def validate_flowspec_rule(rule):
    """Validate FlowSpec syntax"""
    required_keywords = ['announce', 'flow', 'route', 'match', 'then']

    for keyword in required_keywords:
        if keyword not in rule:
            raise ValueError(f"Missing keyword: {keyword}")

    # Additional validation
    if 'source 0.0.0.0/0' in rule and 'discard' in rule:
        raise ValueError("Refusing to blackhole entire internet!")

    return True

Troubleshooting

Issue 1: Rules Not Applied on Routers

Symptoms: FlowSpec rules announced but not filtering traffic

Diagnosis:

# Cisco
show flowspec ipv4
show flowspec ipv4 summary

# Juniper
show firewall filter __flowspec_default_inet__

Common causes:

  • FlowSpec not enabled on router
  • BGP session down
  • FlowSpec validation failing
  • Hardware limitations (TCAM full)

Solutions:

# Enable FlowSpec
router bgp 65000
 address-family ipv4 flowspec
  neighbor 192.168.1.2 activate

# Enable local installation
flowspec
 local-install interface-all

Issue 2: ExaBGP Not Announcing Rules

Symptoms: No BGP UPDATEs sent

Diagnosis:

# Check ExaBGP logs
exabgp -d /etc/exabgp/ddos.conf 2>&1 | tee exabgp.log

# Look for errors
grep ERROR exabgp.log

Common causes:

  • API process not running
  • Syntax error in FlowSpec rule
  • stdout not flushed

Solutions:

# Always flush stdout
sys.stdout.write(rule + "\n")
sys.stdout.flush()  # Critical!

# Check process is running
ps aux | grep ddos_controller

Issue 3: False Positives

Symptoms: Legitimate traffic blocked

Diagnosis:

  • Monitor user complaints
  • Analyze blocked traffic patterns
  • Review FlowSpec match conditions

Solutions:

  • Make rules more specific
  • Use rate-limiting instead of discard
  • Implement whitelisting
  • Adjust detection thresholds

Issue 4: High Latency

Symptoms: Slow rule propagation (> 10 seconds)

Diagnosis:

# Measure BGP convergence time
time exabgp announce-rule.py

# Check BGP timers
show bgp neighbor 192.168.1.2

Solutions:

  • Reduce BGP timers (keepalive, hold-time)
  • Use route reflectors for scalability
  • Optimize detection script performance

Real-World Examples

Example 1: ISP DDoS Mitigation

Scenario: Regional ISP with 100 edge routers

Architecture:

  • Central ExaBGP FlowSpec controller
  • FastNetMon for detection (analyzing sFlow)
  • Route reflectors for BGP scalability

Results:

  • Detection to mitigation: 3 seconds average
  • 50+ attacks blocked per day
  • 99.9% uptime maintained
  • Bandwidth savings: ~500 Gbps/month

Example 2: Enterprise Network Protection

Scenario: Enterprise with multiple data centers

Architecture:

  • ExaBGP + custom Python detection
  • Integration with SIEM (Splunk)
  • Hybrid approach (FlowSpec + cloud scrubbing)

Attack handling:

  • Small attacks (< 1 Gbps): FlowSpec at edge
  • Large attacks (> 1 Gbps): Redirect to cloud scrubbing
  • Auto-escalation based on attack size

Results:

  • 95% of attacks handled at edge
  • Scrubbing costs reduced by 70%
  • No service outages in 12 months

Example 3: Hosting Provider

Scenario: Hosting provider protecting customer VMs

Architecture:

  • ExaBGP per customer (multi-tenant)
  • Custom detection with sFlow/NetFlow analysis
  • Per-customer FlowSpec rules

Features:

  • Customer portal for rule visibility
  • Automatic protection for all customers
  • Granular per-VM filtering

Results:

  • 1000+ customers protected
  • Sub-second mitigation
  • Customer satisfaction: 98%

Next Steps

Learn More

API Documentation

Operations

Ready to deploy DDoS mitigation? See Quick Start to begin →

👻 Ghost written by Claude (Anthropic AI)

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👻 Ghost written by Claude (Anthropic AI)

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