Dynamic routes

Network Administration Guide for Hitachi NAS Platform

Part Number

The NAS server supports ICMP redirects and RIP versions 1 and 2, which enable it to dynamically add routes to its route table.

ICMP redirects

This is a mechanism for routers to convey routing information back to the server. When one router detects that another router offers a better route to a destination, it sends the server a redirect that temporarily overrides the server's routing table. Being router-based, dynamic redirects do not require any configuration, but they can be viewed in the routing table.

The server stores dynamic host routes in its routing table for up to 10 minutes. When a dynamic host route expires, it is removed from the routing table. When subsequent packets are sent to the selected destination, the choice of gateway is determined by the remaining routes in the routing table until the server receives another ICMP redirect. The server creates a dynamic host route for each redirect received. The host route cache can store up to 65,000 dynamic routes at a time.

ICMP router discovery

The NAS server supports ICMP router discovery, which enables it to discover the addresses of routers. ICMP routers periodically multicast their addresses. When the server receives these multicasts, it incorporates the routers into its routing table.

ICMP router discovery is controlled using the CLI command irdp. For more information, see the Command Line Reference. A router discovered using IRDP is propagated to the routing table as a default gateway.

The NAS server discovers IPv6 default gateways through ICMPv6 router advertisements.

RIP (v1 and v2)

RIP is an industry standard protocol that enables servers to automatically discover routes and then update routes in the route table based on updates provided by other network devices. RIP (v1 and v2) is controlled using the CLI command rip. For more information, refer to the Command Line Reference.