How NetCache handles routing

The NetCache appliance does not function as a router

Although the NetCache appliance can have multiple network interfaces, it does not function as a router; that is, the NetCache appliance does not route packets between its interfaces on behalf of other network hosts.

How the NetCache appliance routes its own packets

For routing its own packets, as well as dynamic routes, the NetCache appliance relies on the default route and static routes. Normally, the NetCache appliance learns explicit routes through Internet Control Message Protocol (ICMP) redirect messages received from the default router; you do not need to enter static routes in the NetCache appliance's routing table.

Configuration consideration

You need to enter static routes in the NetCache appliance routing table only if your default gateway is not aware of some addresses and you are not able to route packets to those addresses through RIP or IRDP.

Note
If you implement static routes, disable the Fast IP option (Setup tab > Network > General). The Fast IP option overwrites any static routes that you have specified.

Management of network routing tables

NetCache uses the routed daemon to manage the network routing tables. Routed is a simple routing daemon that is enabled at boot time. Routed uses the Routing Information Protocol (RIP), which listens for packets being exchanged between routers on the network and solicits multicast router discovery Internet Control Message Protocol (ICMP) messages. NetCache uses RIP response packets to update its routing tables. The NetCache routing tables are updated with gateways that are currently recognized on the network, or with gateways that advertise a better metric than at least one of the gateways currently listed in the routing tables.

Configuration consideration

By default, RIP is enabled. Disabling RIP stops NetCache from listening for RIP response packets, and information in the routing table remains static.

About Route Discovery

The Internet Router Discovery Protocol (IRDP), which is an extension of ICMP, enables hosts attached to multicast or broadcast networks to discover the IP addresses of neighboring routers. When the Route Discovery feature on NetCache is enabled, NetCache listens to Router Discovery messages, thereby eliminating the need to manually configure the default gateway. If the default router goes down, IRDP informs NetCache about alternative routers, ensuring that NetCache maintains its connection to the Internet. Only routers that support IRDP can be discovered through the Route Discovery feature.

Configuration consideration

Route Discovery is disabled by default. If your routers are not configured to support IRDP, do not enable this option.