Ospf Metrics; Ospf Security Mechanisms - Avaya 8800 Configuration Manual

OSPF and RIP fundamentals
LSA
type
5 type 5 LSAs [autonomous system external (ASE)
LSAs] describe networks outside of the OSPF domain,
are originated by the ASBR, and are passed between
areas. In stub and NSSA areas, type 5 LSA routes are
replaced with a single default route.
6 Type 6 LSAs (group membership LSAs) identify the
location of multicast group members in multicast
OSPF.
7 Type 7 LSAs are used in OSPF NSSAs to import
external routes.

OSPF metrics

For OSPF, the best path to a destination is the path that offers the least-cost metric (least-cost
delay). OSPF cost metrics are configurable, so you can specify preferred paths. You can
configure metric speed globally or for specific ports and interfaces on your network. In addition,
you can control redistribution options between nonOSPF interfaces and OSPF interfaces.
Default metric speeds are assigned for different port types, such as 10 Mbit/s or 100 Mbit/s
ports. On an Ethernet Routing Switch 8800/8600, you can specify a new metric speed for an
IP interface. An IP interface can be a brouter port or a VLAN.
Important:
On the Ethernet Routing Switch 8800/8600, when you enable a port for OSPF routing, the
default metric in the port window in Enterprise Device Manager is 0. A value of 0 (zero)
means that the port uses the default metrics for port types that are specified on the OSPF
general window.
RFC 1583 states:
"OSPF supports two types of external metrics. Type 1 external metrics are equivalent to the
link state metric. Type 2 external metrics are greater than the cost of any path internal to the
AS. Use of Type 2 external metrics assumes that routing between ASs is the major cost of
routing a packet, and eliminates the need for conversion of external costs to internal link state
metrics."
"Both Type 1 and Type 2 external metrics can be present in the AS at the same time. In that
event, Type 1 external metrics always take precedence."

OSPF security mechanisms

The Avaya Ethernet Routing Switch 8800/8600 implementation of OSPF includes security
mechanisms to prevent unauthorized routers from attacking the OSPF routing domain. These
52 Configuration — OSPF and RIP
Description Area of distribution
Passed between areas
Passed between areas
Translated between
areas
June 2011