User`s guide

8-18 Preliminary November 23, 1998 MultiVoice Gateway for the MAX— User’s Guide
Configuring IP Routing
Configuring IP routes and preferences
Static route preferences
By default, static routes and RIP routes have the same preference, so they compete equally.
ICMP redirects take precedence over both, and OSPF take precedence over everything. If a
dynamic route’s preference is lower than that of the static route, the dynamic route can
overwrite (hide) a static route to the same network. In the IP routing table, the hidden static
route has an h flag, indicating that it is inactive. The active, dynamically learned route is also in
the routing table. However, dynamic routes age and, if no updates are received, eventually
expire. In that case, the hidden static route reappears in the routing table.
RIP and OSPF preferences
Because OSPF typically involves a complex environment, its router configuration is described
in Chapter 9, “Configuring OSPF Routing.”
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.
Metrics for routes learned from RIP
The RipAseType parameter can specify 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 it eliminates the need for conversion of external costs to
internal link-state metrics.
Examples of static route configuration
The section provides information about configuring the IP default route and configuring a
static route to a remote subnet. For an example of the Ethernet profile configuration of the
MultiVoice Gateway unit’s local IP interface, see “Configuring the MultiVoice Gateway IP
interface on a subnet” on page 8-10.
Configuring the default route
If no routes exist for the destination address of a packet, the MultiVoice Gateway forwards the
packet to the default route. Most sites use the default route to specify a local IP router (such as
a Cisco router or a UNIX host running the route daemon) to off-load routing tasks to other
devices.
Note: If the MultiVoice Gateway does not have a default route, it drops packets for which it
has no route.
1 Open the first IP Route profile (the route named Default) and activate it:
Ethernet
Static Rtes
Name=Default