RuggedCom RuggedRouter RX1100 - Manual (Page 162)

17. Configuring Dynamic Routing
Revision 1.14.3 162 RX1000/RX1100™
17.1.5. Key OSPF And RIP Parameters
17.1.5.1. Network Areas
Network areas determine the regions within which routes are distributed to other routers. The subnets
at a particular router can be added to its OSPF Area. The router will advertise these subnets to all
routers in its area.
Note
OSPF areas must be designed such that no single link failure will cause the network to be split
into two disjoint networks.
A router can be part of multiple areas and function as a gateway between areas. When multiple areas
are used on a network, area 0 is the backbone area. All areas must have a router connecting them
to area 0.
17.1.5.2. Router-ID
Defines the ID of the router. By default this is the highest IP assigned to the router. It is often a good
idea to configure this value manually to avoid the router-id changing if interfaces are added or deleted
from the router. During elections for designated router, the router-id is one of the values used to pick
the winner. Keeping the router-id fixed will avoid any unexpected changes in the election of the master
router.
17.1.5.3. Hello Interval and Dead Interval
The hello interval is the time between transmission of OSPF Hello packets. The dead interval is the
time to wait without seeing an OSPF Hello packet before declaring a neighboring router dead and
discarding its routes. It is recommended that the dead interval be at least four times the hello interval
for reliable operation.
Lower values of these settings will help to speed up the change in network routes when the topology
of the network changes. It will also increase the load on the router and the links, due to higher traffic
caused by the increase in messages. Lower values will also put limits on the number of routes that
can be distributed within an area, as will running over slower links.
Note
OSPF will not work properly if the Hello Interval and Dead Interval are not identical on every router
in an area.
17.1.5.4. Active/Passive Interface Default
OSPF regards router interfaces as either passive or active, sending OSPF messages on active
interfaces and ignoring passive interfaces. By default, newly created interfaces are viewed as passive
from OSPF until they are configured active. This is more efficient and secure for the router. The
default type for new interfaces is controlled by the passive interface default option in the OSPF Global
Parameters.