Routers

A router is what gives a tenant network (and its subnets) internet access. VMs attached to a tenant subnet can't reach the public internet on their own — they're on a private L2 segment. A router bridges that segment to the region's external network, doing NAT for outbound traffic and (optionally) hosting floating IPs for inbound.

When you need a router

• Public-facing VMs on a tenant network. Attach a router, then allocate + attach a floating IP. Outbound traffic NATs through the router; inbound on the floating IP routes back to the VM.
• Mixed private/public app tiers. Web tier sits behind a router with a floating IP; app + db tiers stay private and reach the internet (for things like package updates) via the router's source-NAT.
• Multi-subnet routing. A router can serve multiple subnets simultaneously. Traffic between two subnets on the same router is intra-VPC, never leaves NimbusNexus, and isn't billed as egress.

If you're attaching VMs directly to the external network, you don't need a router — the external network IS the gateway.

SNAT, DNAT, and floating IPs

A router has one external gateway connection (to the region's external network) and zero or more internal connections (to tenant subnets).

• Outbound from a private VM → router does source-NAT to the router's external IP. Multiple private VMs share that one external IP for outbound.
• Inbound to a floating IP → router does destination-NAT to the private VM the floating IP is attached to. The private VM sees the original source IP (we preserve client IP through the NAT for inbound; only outbound SNATs).

You don't configure NAT directly; the router handles it based on which subnets are attached and which floating IPs you've created.

Static routes

A router carries a static-route table you can populate for non-default destinations — e.g. routing one subnet's traffic for a specific CIDR through a different VM (a VPN appliance, a transparent proxy). Most users never touch this; it's there for the advanced VPC layouts that need it.

What's next

• Networks and Subnets — what routers connect.
• Floating IPs — inbound public addresses that ride on a router.
• Security groups — the firewall layer applied at the VM interface (the router itself doesn't filter).