Configuring Routes

Context

The routes forwarded by a tunnel must be available on Spokes and the Hub so that packets encapsulated with mGRE can be forwarded correctly. These routes can be static routes or dynamic routes.

DSVPN supports the following route learning modes:

Route learning between Spokes (non-shortcut)

The next-hop address of the route from the source Spoke to the destination Spoke is the tunnel address of the destination Spoke, and each Spoke needs to learn the route to the remote end. This consumes many CPU and memory resources and requires large routing tables and high performance on Spokes. In practice, the Spokes have low performance and store a limited number of routes. The route learning solution applies to small- and medium-sized networks where there are fewer network nodes and a small number of routes.

mGRE tunnels between Spokes are set up in non-shortcut mode.
Spoke routes summarized to the Hub (shortcut mode)

The next-hop address of the route from the source Spoke to the destination Spoke is the tunnel address of the Hub, and Spokes only need to store routes to the Hub. The number of routes of Spokes is reduced, so the route learning solution applies to large-sized networks with many Spokes.

mGRE tunnels between Spokes are set up in shortcut mode.

Static routes and dynamic routing protocols can be deployed in the preceding two route learning modes. DSVPN supports RIP, OSPF and BGP.

When there are many Spokes and static routes are configured, many static routes need to be configured on the Hub. When Spokes change, static route configuration needs to be changed on the Hub. It is difficult to maintain the network. Dynamic routing protocols are limited by the number of supported neighbors, and route flapping affects network quality. DSVPN route injection can be deployed. When Spokes are registered with the Hub, extension fields of NHRP Registration Request packets carry routing information of Spokes. The Hub dynamically generates routes to Spokes based on the learned routing information. This reduces the configuration and maintenance workload, and prevents problems of dynamic routing protocols.

Perform the following configurations on the Hub and Spokes.

Procedure

Configure routes between Spokes and between the Hub and Spokes

Configuring static routes
1. Run the system-view command to enter the system view.
2. Run the ip route-static ip-address { mask | mask-length } nexthop-address [ description text ] command to configure a static route.
- When Spokes learn routes from each other, the next-hop address of the static route from a Spoke to the Hub or another Spoke is the tunnel address of the remote device.
- When routes of Spokes are summarized to the Hub, the next-hop address of the static route from a Spoke to the Hub or another Spoke is the tunnel address of the Hub.

Configuring dynamic routes

Run the system-view command to enter the system view.

Configure dynamic routes.

You can use RIP, BGP, or OSPF. The configuration is not mentioned here. For details on how to configure dynamic routes, see "IP Routing" in the Configuration Guide.

When configuring different dynamic routing protocols, note the following points.

Route Learning Mode and Routing Protocol	RIP	OSPF	BGP
Spokes learn routes from each other.	Disable split horizon and automatic route summarization on the mGRE interface of the Hub.	Run the ospf network-type broadcast command to set the OSPF network type to broadcast on the Hub and Spokes.	Do not configure route summarization on the Hub.
Routes of Spokes are summarized to the Hub.	Enable split horizon and automatic route summarization on the mGRE interface of the Hub.	Run the ospf network-type p2mp command to set the OSPF network type to P2MP on the hub and spokes.	Configure route summarization on the Hub.

(Optional) Configure route injection.

When there are many subnets of Spokes, perform this step so that routes from the Hub to subnets of Spokes are dynamically generated. This function reduces the configuration and maintenance workload of the Hub.

The route injection function is used to generate only routes from the Hub to subnets of Spokes. The routes between Spokes and the Hub and between Spokes still need to be configured. For details, see Configuring static routes or Configuring dynamic routes.

DSVPN Node	Route Injection Configuration
Spoke	Run the system-view command to enter the system view. Run the interface tunnel interface-number command to enter the tunnel interface view. Run the nhrp reverse-route ip-address mask { mask \| mask-length } command to configure the subnet route that needs to be injected to the Hub.
Hub	Run the system-view command to enter the system view. Run the interface tunnel interface-number command to enter the tunnel interface view. Run the nhrp hub reverse-route enable command to enable route injection. Run the nhrp hub reverse-route preference preference-value command to set the precedence of the injected route.