Networking

Every cloud instance is connected to the internet via a public IPv4 address by default. You can extend your network configuration with IPv6, private networks, firewalls, and floating IPs to build secure, production-ready architectures.

Public IPv4

Every instance receives one public IPv4 address on creation, allocated from the regional IP pool.

How It Works

• Static assignment — Your IP is statically configured as a /32 address with the host node's gateway. It is not assigned via DHCP.
• Persistent — The IP stays with the instance until it is destroyed.
• Reverse DNS — Set a custom PTR record for your IP from the instance networking tab. Essential for mail servers and services that require proper rDNS.
• Copy button — Click the IP on the instance detail page to copy it to your clipboard.

# Connect to your instance
ssh root@203.0.113.42

Reverse DNS Configuration

1. Navigate to your instance → Networking tab
2. Click Set rDNS next to the IPv4 address
3. Enter your desired PTR record (e.g., mail.example.com)
4. Save — changes propagate within 5-15 minutes

Public IPv6

IPv6 is optional and free for all cloud instances. Each instance that enables IPv6 receives a /64 subnet.

Enabling IPv6

• During creation — Toggle Enable IPv6 in the networking section of the instance creation form.
• After creation — IPv6 can be enabled from the instance networking tab (requires a reboot).

IPv6 Details

Private Networks

Private networks let your instances communicate over an isolated, internal network. Traffic stays within the datacenter — no internet routing, lower latency, and zero bandwidth charges.

Creating a Private Network

1. Go to your project → Networking
2. Click Create Network
3. Enter a name and subnet (e.g., 10.0.0.0/24)
4. Click Create

Attaching Instances

During creation: Enable Private Network in the networking section and select your network from the dropdown.

After creation: Navigate to your instance → Networking tab → Private Networks → Attach Network.

How It Works

Each instance attached to a private network gets:

• A second network interface (net1) on the private bridge (vmbr1)
• An automatically assigned private IP from your subnet
• Layer 2 connectivity with other instances on the same network

Use Cases

• Database isolation — Keep your database on a private network, accessible only from your application servers. No public exposure.
• Microservices — Service-to-service communication without exposing endpoints to the internet.
• Cluster communication — Kubernetes nodes, Docker Swarm workers, or database replicas communicating over fast, private links.

Example: Isolate a Database Server

1. Create a private network with subnet 10.0.0.0/24
2. Deploy your app server and attach it to the private network (gets 10.0.0.2)
3. Deploy your database server and attach it to the private network (gets 10.0.0.3)
4. Configure your database to listen only on 10.0.0.3
5. Configure your app to connect to 10.0.0.3:5432 (PostgreSQL) or 10.0.0.3:3306 (MySQL)

# From your app server, verify connectivity
ping 10.0.0.3

# Connect to your database over the private network
psql -h 10.0.0.3 -U myuser -d mydb

See Private Networks for full documentation.

Firewalls

The cloud firewall lets you control inbound and outbound traffic to your instances at the network level. Rules are applied before traffic reaches your instance, providing an additional layer of security.

Default Behavior

Firewalls are disabled by default — all inbound and outbound traffic is allowed. Once you enable the firewall, you define rules to control access.

Enabling the Firewall

1. Navigate to your instance → Networking tab → Firewall
2. Toggle Enable Firewall to on
3. Set your default inbound and outbound policies
4. Add rules as needed

Policies

Adding Rules

Each rule has the following fields:

Security Groups

Security groups are reusable sets of firewall rules that you can apply to multiple instances. Instead of duplicating rules across instances, create a security group once and attach it.

1. Navigate to Networking → Security Groups
2. Create a group (e.g., web-servers)
3. Add rules to the group
4. Attach the group to any instance's firewall

Example: Allow SSH Only

Set inbound policy to DROP, then add one rule:

# Test SSH access
ssh root@your-instance-ip
# All other inbound traffic is silently dropped

Example: Web Server (HTTP + HTTPS)

Set inbound policy to DROP, then add these rules:

Example: Database Isolation with Private Network

Keep your database accessible only from your private network:

1. Deploy the database instance with a private network (10.0.0.0/24)
2. Enable the firewall with inbound policy DROP
3. Add rules:

Floating IPs

Floating IPs are reserved public IP addresses that can be reassigned between instances in the same region. They enable instant failover, high availability, and seamless IP portability.

How It Works

1. Allocate a floating IP from the regional pool
2. Attach it to any running instance
3. Detach and reattach to another instance for failover — no DNS changes needed

Pricing

Use Cases

• High availability — Reassign the IP to a standby instance if the primary fails
• Blue-green deployments — Switch traffic between versions without DNS propagation
• Mail servers — Dedicated IP with proper rDNS for email deliverability

API Example

# Reserve a floating IP
curl -X POST https://api.hostupcloud.com/v1/floating-ips \
  -H "Authorization: Bearer $API_TOKEN" \
  -H "Content-Type: application/json" \
  -d '{"region": "in-blr", "type": "ipv4"}'

# Attach to an instance
curl -X POST https://api.hostupcloud.com/v1/floating-ips/{ip-id}/attach \
  -H "Authorization: Bearer $API_TOKEN" \
  -H "Content-Type: application/json" \
  -d '{"instance_id": "your-instance-id"}'

# Detach from an instance
curl -X POST https://api.hostupcloud.com/v1/floating-ips/{ip-id}/detach \
  -H "Authorization: Bearer $API_TOKEN"

See Floating IPs for full documentation including subnet pricing and rDNS configuration.

Network Summary

Next Steps

• Configure Storage for volumes, snapshots, and backups
• Upload SSH Keys for secure instance access
• Review Network & Connectivity for datacenter-level networking details
• Learn about Security & Compliance for data protection