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Chapter 1
Overview
Static Routes
Static routes can be configured to the P333R. They are never timed-out, or lost over
reboot, and can only be removed by manual configuration. Deletion (by
configuration) of the IP interface deletes the static routes using this interface as well.
A static route becomes inactive if the interface over which it is defined is disabled.
When the interface is enabled, the static route becomes active again.
Static routes can only be configured for remote destinations, i.e. destinations that
are reachable via another router as a next hop. The next hop router must belong to
one of the directly attached networks for which P333R has an IP interface. "Local"
static routes, such as those that have no next hop, are not allowed.
Two kinds of static routes can be configured, High Preference static routes which are
preferred to routes learned from any routing protocol and Low Preference static
routes which are used temporarily until the route is learned from a routing protocol.
By default, a static route has Low Preference.
Static routes can be advertised by routing protocols (i.e. RIP, OSPF) as described
under Route redistribution.
Static routes also support load-balancing similar to OSPF. A static route can be
configured with multiple next hops so that traffic is split between these next hops.
This can be used for example to load-balance traffic between several firewalls which
serve as the default gateway.
Route Redistribution
Route redistribution is the interaction of multiple routing protocols. OSPF and RIP
can be operated concurrently in P333R. In this case, P333R can be configured to
redistribute routes learned from one protocol into the domain of the other routing
protocol. Similarly, static routes may be redistributed to RIP and to OSPF. Route
redistribution should not be configured carelessly, as it involves metric changes and
might cause routing loops in the presence of other routes with incompatible
schemes for route redistribution and route preferences.
The P333R scheme for metric translation in route redistribution is as follows:
•
Static to RIP metric configurable (default 1)
•
OSPF internal metric N to RIP metric 1
•
OSPF external type 1 metric N to RIP metric 1
•
OSPF external type 2 metric N to RIP metric N+1
•
Static to OSPF external type 2, metric configurable (default 1)
•
RIP metric N to OSPF external type 2, metric N
•
Direct to OSPF external type 2, metric 1.
By default, the P333R does not redistribute routes between OSPF and RIP.
Redistribution from one protocol to the other can be configured. Static routes are, by
default, redistributed to RIP and OSPF. P333R allows the user to globally disable
redistribution of static routes to RIP, and separately to globally disable
12
Avaya P333R User's Guide
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