Allied Telesis AT-S63 - Manual (Page 313)

AT-S63 Management Software Features Guide
Section VII: Routing 313
Static Routes
In order for the switch to route an IPv4 packet to a remote network or
subnet, there must be a route to the destination in the routing table of the
switch. The route must consist of the IP address of the remote destination
and the IP address of the next hop to reaching the destination.
One type of route to a remote destination is referred to as a static route.
You create static routes by manually entering them into the routing table.
Static routes are never deleted from the routing table by the switch, even
when they are inactive.
When you create a static route, the switch’s management software
automatically adds it to the interface that is a part of the same subnet as
the next hop of the route. Consequently, before you can create a static
route, the switch must have a routing interface that is a member of the
same subnet as the next hop of the route.
For example, assume a switch supported four subnets with four interfaces
named VLAN4-0, VLAN11-0, VLAN12-0, and VLAN12-1. If you created a
static route to a remote destination that had as its next hop an IP address
in the subnet of the VLAN4-0 interface, the switch would automatically add
the route to the VLAN4-0 interface.
A new static route immediately becomes available for all of the interfaces
on a switch to use for routing packets to the remote subnet. For example,
referring to the previous example, a static route added to the VLAN4-0
interface would be available to all the other interfaces on the same switch.
The switch can store up to 1024 static routes.
A static route is functional as soon as it is added to an interface and cannot
be disabled. You must delete a route from the table to stop a switch from
routing packets with the route.
Static routes have a parameter called the metric that is a measurement of
the cost of the switch when it forwards packets to the remote destination
specified in the static route. The metric or cost is simply the hop count. The
default setting for a static route is one hop. The value can be set higher to
make a static route more costly. Networks, subnets, and nodes directly
connected to a router have a hop count of 0.
When the switch receives a packet from a remote subnet, it increases the
metric or cost of the packet before forwarding it on to the next hop. A
remote destination with a hop count of 16 is considered unreachable.
Static routes also have a parameter for assigning a preference value. The
switch uses this value to select the active routes when there are multiple
static or dynamic routes in the routing table to the same remote