Consistent Use Of Routers That Support Route Aggregation; Interaction With Sap; Metrics Used With Aggregated Routes - Novell NetWare 6 Manual

Consistent Use of Routers that Support Route
Aggregation

Interaction with SAP

Metrics Used with Aggregated Routes

36
Internetwork Packet Exchange
Route aggregation into an NLSP area is possible only if all routers in that area
support address summaries. Routers that do not support route aggregation do
not recognize destination addresses for aggregated routes; they forward
packets to the default route or drop packets if no default route is configured.
Because routers that support route aggregation route packets differently from
routers that do not support route aggregation, routing loops can occur.
Therefore, if a router that supports route aggregation detects that the next-hop
router on the path to an aggregated destination is a router that does not support
route aggregation, it will drop the packet.
Without route aggregation, if a service is announced with an address that is not
explicitly reachable, RIP assumes the service is unreachable. When NLSP and
RIP are used with route aggregation, SAP is accepted, provided a packet can
be forwarded to the corresponding network number. A packet can be
forwarded when there is a default route and address summary or when there is
an explicit advertisement of that network number.
This feature is disabled by default. It can be enabled by entering the following
command after IPXRTR.NLM has been loaded:
SET REQUIRED NETWORK FOR SERVICES=ON
If a router is configured to introduce an address summary into an NLSP area,
it does so, with the number of ticks equal to 1 (as the default), an area count
equal to 6 (as the default), and the ability to configure both parameters with a
different value. The area count is the number of areas through which the route
information is allowed to propagate. As the route information is passed
through each of these areas, the area count is decremented by one. This
enables the initial sending router to control the spread of information through
all NLSP areas that are connected to each other.
Address summaries are not exported from an NLSP area into a RIP cloud
because the capability to express a summarized route within RIP does not
exist. In addition, updating RIP with this capability is not cost-effective
because the default route is sufficient for RIP.