Dedicated Server Network: Setup and Optimization

Dedicated servers provide multiple network options: multiple public IPs, private networks, bonded connections, and DDoS mitigation. Proper network configuration ensures redundancy, high availability, and protection against bandwidth exhaustion. This guide covers enterprise-grade network setup for dedicated servers.

Network Overview

Dedicated server network capabilities:**

• Multiple IPs: Up to /30 subnet (4 IPs) or larger blocks
• Bond ports: Redundant connections (Port 1 + Port 2 = combined bandwidth)
• Private network: 10.0.0.0/8, 192.168.0.0/16 for inter-server communication
• VLAN support: Virtual LAN isolation
• DDoS mitigation: Upstream filtering (Corero, Arbor)

IP Address Assignment

Typical dedicated server IP allocation:**

• Primary public IP: 203.0.113.25
• Secondary public IPs: 203.0.113.26-28 (up to /28 subnet)
• Gateway IP: 203.0.113.1 (for routing)
• Broadcast: 203.0.113.31

Configure static IP on Debian/Ubuntu:**

# Edit /etc/netplan/00-installer-config.yaml
network:
  version: 2
  ethernets:
    eth0:
      dhcp4: no
      addresses:
        - 203.0.113.25/28
        - 203.0.113.26/28
        - 203.0.113.27/28
      routes:
        - to: 0.0.0.0/0
          via: 203.0.113.1
      nameservers:
        addresses:
          - 8.8.8.8
          - 8.8.4.4

# Apply changes
netplan apply

Configure on CentOS/RHEL:**

# /etc/sysconfig/network-scripts/ifcfg-eth0
DEVICE=eth0
BOOTPROTO=none
ONBOOT=yes
IPADDR=203.0.113.25
NETMASK=255.255.255.240
GATEWAY=203.0.113.1
DNS1=8.8.8.8

# Restart network
systemctl restart network

Network Bonding

Combine multiple network ports for redundancy:**

Bonding modes:**

• balance-rr: Round-robin, distributes traffic
• active-backup: One active, others standby (recommended)
• balance-alb: Adaptive load balancing
• 802.3ad: LACP (requires switch support)

Setup active-backup bonding:**

# /etc/netplan/00-installer-config.yaml
network:
  version: 2
  ethernets:
    eth0: {}
    eth1: {}
  bonds:
    bond0:
      dhcp4: no
      interfaces: [eth0, eth1]
      parameters:
        mode: active-backup
        mii-monitor-interval: 100
      addresses:
        - 203.0.113.25/28
      routes:
        - to: 0.0.0.0/0
          via: 203.0.113.1

# Apply
netplan apply

# Verify
cat /proc/net/bonding/bond0

VLAN Configuration

Virtual LANs for network isolation:**

Create VLAN interface:**

# /etc/netplan/00-installer-config.yaml
network:
  version: 2
  ethernets:
    eth0:
      dhcp4: no
  vlans:
    vlan100:
      id: 100
      link: eth0
      addresses:
        - 192.168.100.10/24
      routes:
        - to: 0.0.0.0/0
          via: 192.168.100.1

# Apply
netplan apply

# Verify
ip link show vlan100

DNS Configuration

Set DNS nameservers:**

# /etc/netplan/00-installer-config.yaml
network:
  version: 2
  ethernets:
    eth0:
      dhcp4: no
      addresses:
        - 203.0.113.25/28
      nameservers:
        addresses:
          - 8.8.8.8
          - 8.8.4.4
        search:
          - example.com

# Or edit /etc/resolv.conf (temporary)
nameserver 8.8.8.8
nameserver 8.8.4.4

Traffic Shaping

Rate limit traffic to prevent exhaustion:**

# Limit port 80 to 100Mbps
tc qdisc add dev eth0 root tbf rate 100mbit burst 32kbit latency 400ms

# Verify
tc qdisc show

# Remove limit
tc qdisc del dev eth0 root

DDoS mitigation (upstream):**

• Contact UnderHost NOC for DDoS protection activation
• Upstream filtering (Corero, Arbor) blocks attacks before reaching server
• Protects entire dedicated server from volumetric attacks

Monitor Network

Monitor network interfaces:**

# Check interface status
ip link show

# Check IP assignments
ip addr show

# Monitor traffic in real-time
iftop -n

# Or use mtr for route tracing
mtr -c 100 8.8.8.8

Monitor bandwidth usage:**

# Install vnstat
apt install vnstat
systemctl enable vnstat
systemctl start vnstat

# View statistics
vnstat -h        # Hourly
vnstat -d        # Daily
vnstat -m        # Monthly

Optimize for Performance

Network buffer tuning:**

# /etc/sysctl.conf
# Increase TCP buffer sizes
net.core.rmem_max = 134217728
net.core.wmem_max = 134217728
net.ipv4.tcp_rmem = 4096 87380 67108864
net.ipv4.tcp_wmem = 4096 65536 67108864

# TCP optimization
net.ipv4.tcp_tw_reuse = 1
net.ipv4.tcp_fin_timeout = 30
net.core.netdev_max_backlog = 5000

# Apply changes
sysctl -p

Jumbo frames (MTU 9000) for 10Gbps links:**

# Set MTU to 9000 for eth0
ip link set dev eth0 mtu 9000

# Verify
ip link show eth0 | grep mtu

# Make permanent in netplan/ifcfg

Related: VPS networking | Static IP setup | Firewall setup | Bandwidth management

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