There may be scenarios where you do not want to run a Nexodus agent on every host that you intend to have connectivity to a Nexodus VPC. It is possible to have a host act as a Network Router to provide connectivity between a Nexodus network and a subnet a Nexodus agent node can access.
Connect any nodes on your network or connect sites
Any Linux Nexodus device running Nexodus can be a network router. The forwarding and NAT are performed with netlink and netfilter.
The situations where this can be useful are wide-ranging. They can span from connecting a remote cluster, an air-gapped EC2 VPC, or connecting any number of remote sites that you may not want to or cannot run an agent. SD-WAN solutions can be expensive and overly complex. This can be a lightweight alternative.
- You simply specify the network prefix you want to advertise and Nexodus will use the physical interface that contains the default route to connect to the non-Nexodus nodes.
nexd router --advertise-cidr 192.168.100.0/24 --network-router
- If you are running nexd in a container, additional capabilities need to be added to the container at runtime. Here is an example on how to start a container with IPv4/IPv6 forwarding capabilities enabled.
docker run --rm -it --cap-add SYS_MODULE --cap-add NET_ADMIN --cap-add NET_RAW \
--sysctl net.ipv4.ip_forward=1 \
--sysctl net.ipv6.conf.all.disable_ipv6=0 \
--sysctl net.ipv6.conf.all.forwarding=1 \
Note Nexodus accepts as many networks as you want to specify in the
--advertise-cidr=192.168.1.0/24 --advertise-cidr 192.168.100.0/24 --advertise-cidr 172.16.100.0/24 ...configuration. This means you can advertise as many subnets as you want from the Nexodus device running as a network router.
By default, Nexodus network routers perform NAT, specifically, source NAT for devices coming from a Nexodus mesh with a destination of one of the devices not running the Nexodus agent. This enables connectivity to those devices without any configuration on the devices.
You have the option to disable NAT with
--disable-nat which will cause the remote non-Nexodus devices to receive traffic from the Nexodus agent devices without any address translations. This mode requires routes to be added (or redistributed in your network IGP) for hosts in
192.168.1.0/24 to reach Nexodus nodes
100.100.0.0/16 via the
Nexodus Network Router eth0 ip of
The subnet exposed to the Nexodus VPC may be a physical network the host is connected to, but it can also be a network local to the host. This works well for exposing a local subnet used for containers running on that host. A demo of this use case for containers can be found in scenarios/containers-on-nodes.md.
Additional details and diagrams are located in the network router design documentation docs/development/design/network-router