DomR

DomR, short for domain router, refers to a specialized virtual router used in cloud networking environments, most notably in Apache CloudStack. It runs as a system virtual machine on hypervisor hosts and serves as the network appliance for user networks, providing essential services at the network edge.

Functionally, a domR delivers DHCP, DNS, NAT, firewall filtering, and routing between a guest (user) network and the underlying physical network. It may also handle VPN termination and port forwarding, with traffic isolation achieved through VLAN-based network segmentation. Each user network is typically backed by one or more domR instances to ensure connectivity and resilience.

Deployment and management of domR instances are automated within CloudStack. The management server deploys domR VMs on available hosts across supported hypervisors such as KVM, Xen, and VMware. The lifecycle of domR VMs—creation, monitoring, and replacement upon failure—is handled by the CloudStack control plane, with status accessible via the CloudStack user interface or API.

Relation to system virtual routers: In CloudStack terminology, the domR implements the functionality of the system virtual router for user networks. The domR-based approach provides the routing, NAT, and gateway services that connect guest networks to the public network while maintaining network isolation and policy enforcement.

Security and performance considerations: Because a domR runs as a dedicated VM, its performance depends on the resources allocated on the host and the capacity of the network links. DomRs are typically kept lightweight to minimize overhead and ensure predictable routing performance for multiple user networks.

See also: CloudStack, system virtual router, NAT, DHCP, VLAN.