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Introduction
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CopperLink CL2300 User Manual
12
• IP Routing
Introduction
The Trinity IP Routing facility consists of the two major functionalities: Basic Routing and Policy Routing.
Basic Routing
Under Basic Routing is to be understood the destination IP address based next-hop determination. The next-
hop or gateway selection is done by matching a set of routing rules entered by the user (static-route), received
through a routing-protocol (dynamic-route) or added by the system (system-route). Routing entries which
specify a gateway as next-hop are also called gateway-routes. Networks that are directly reachable through a
device’s network-port are specified through interface-routes. Instead of a gateway they specify an outgoing
interface.
In the context ip configuration mode exists a system created routing-table called DEFAULT. This table con-
tains all Basic Routing information and cannot be deleted by the user. Actually it is possible to created addi-
tional routing-tables with a user defined name but such user-created tables are part of the Policy Routing and
do not have any use in Basic Routing.
All Basic Routing features are available for IPv4 as well as for IPv6.
Static Routes
These are user managed gateway and interface routes and are getting exported in the running-config. In the
output of the show route command they are flagged with an “R”. Another flag “U” indicates if the route is up
or not. A static gateway-route is becoming active (up) if the gateway is reachable. For this we need the follow-
ing conditions:
•
At least one IP address in the gateway’s network has to be configured.
•
The IP interface which owns the IP address has to be bound from a network-port.
•
The network-port’s link state has to be up.
A static interface-route is becoming active (up) if:
•
The specified outgoing interface is bound from a network-port.
•
The specified outgoing interface has at least one IP address configured.
•
The network-port’s link state has to be up.
Configuring static routes
A route is clearly identified by its destination address/mask combination and the metric. That means it is
allowed to configure several time the same destination, using the same or different gateways, but with a differ-
ent metric value. The metric in a static route has the meaning of a priority where lower value means higher pri-
ority.
Static route differentiation by metric is useful if a destination network is reachable through different gateways.
Usually gateways are located in the same network as the device itself. If the link to the gateway with lowest met-
ric is going down, this static-route is becoming unavailable. In that case the device’s router will select the route
to the destination with the next higher metric and another gateway is going to be used.