User`s guide

Configuring IP Routing
Configuring IP routes and preferences
MultiVoice Gateway for the MAX— User’s Guide Preliminary November 23, 1998 8-17
Route’s gateway address
The Gateway parameter specifies the IP address of the router or interface through which to
reach the target network.
Metrics, costs, and preferences
The Metric parameter specifies the hop count (a number of from 1 to 15) for this route. Hop
count refers to the number of routers that have to be crossed to reach the destination. For
example, reaching a destination with a hop count of 10 requires (theoretically) crossing 10
routers. A route with a shorter hop count to a destination is more desirable than one with a
larger hop count, since it most likely is a shorter, faster route.
You can configure the Metric parameter as virtual hop count. To define which routes are more
desirable, regardless of the actual number of routers the route crosses. The higher the metric,
the less likely is the MultiVoice Gateway to use the route.
The Cost parameter specifies the cost of an OSPF link. Cost is a configurable metric that can
take into account the speed of the link and other issues. The lower the cost, the more likely is
the interface to be used to forward data traffic. (For details, see Chapter 9, “Configuring OSPF
Routing.”)
The Preference parameter specifies a route preference. Zero is the default for connected routes
(such as the Ethernet). When choosing which route to use, the router first compares the
preference values, preferring the lowest number. If the preference values are equal, the router
compares the metric values, and uses the route with the lowest metric. The value of 255 means
“Do not use this route.” (For details, see “Route preferences and metrics” on page 8-4.)
Tagging routes learned from RIP
The Rip-Tag field is attached to all routes learned from RIP in OSPF updates. The tag is a
hexadecimal number that can be used by border routers to filter the record.
Type-1 or type-2 metrics for routes learned from RIP
The Rip Ase Type parameter can be set to Type-1 or Type-2. Type-1 is a metric expressed in
the same units as the link-state metric (the same units as interface cost). Type-2 is considered
larger than any link-state path. It assumes that routing between autonomous systems is the
major cost of routing a packet, and eliminates the need for conversion of external costs to
internal link-state metrics.
Making a route private
Private routes are used internally but are not advertised.
Note: Typically, default routes should not be advertised to other routers. They are designed
for the internal use of the specific router on which they are configured.
A connected route for the Ethernet IP interface
The IP Adrs parameter specifies the MultiVoice Gateway unit’s IP address on the local
Ethernet. The MultiVoice Gateway creates a route for this address at system startup.