Authentication.
All OSPF protocol exchanges can, if required, be authenticated. This means that only routers with
the correct authentication can join an AS. Different authentication schemes can be used and with
NetDefendOS the scheme can be either a passphrase or an MD5 digest.
It is possible to configure separate authentication methods for each AS.
OSPF Areas
An OSPF Area consists of networks and hosts within an AS that have been grouped together.
Routers that are only within an area are called internal routers. All interfaces on internal routers are
directly connected to networks within the area.
The topology of an area is hidden from the rest of the AS. This information hiding reduces the
amount of routing traffic exchanged. Also, routing within the area is determined only by the area's
own topology, lending the area protection from bad routing data. An area is a generalization of an IP
sub netted network.
In NetDefendOS, areas are defined by OSPF Area objects and are added to the AS which is itself
defined by an OSPF Router object. There can be more than one area within an AS so multiple OSPF
Area objects could be added to a single OSPF Router. In most cases, one is enough and it should be
defined separately on each NetDefend Firewall which will be part of the OSPF network.
This NetDefendOS object is described further in Section 4.5.3.2, “OSPF Area”.
OSPF Area Components
A summary of OSPF components related to an area is given below:
ABRs
Area Border Routers are routers that have interfaces connected to more than
one area. These maintain a separate topological database for each area to
which they have an interface.
ASBRs
Routers that exchange routing information with routers in other Autonomous
Systems are called Autonomous System Boundary Routers. They advertise
externally learned routes throughout the Autonomous System.
Backbone Areas
All OSPF networks need to have at least the Backbone Area which is the
OSPF area with an ID of 0. This is the area that other related areas should be
connected to. The backbone ensures routing information is distributed
between connected areas. When an area is not directly connected to the
backbone it needs a virtual link to it.
OSPF networks should be designed by beginning with the backbone.
Stub Areas
Stub areas are areas through which or into which AS external advertisements
are not flooded. When an area is configured as a stub area, the router will
automatically advertise a default route so that routers in the stub area can
reach destinations outside the area.
Transit Areas
Transit areas are used to pass traffic from an area that is not directly
connected to the backbone area.
The Designated Router
Each OSPF broadcast network has a single Designated Router (DR) and a single Backup Designated
4.5.2. OSPF Concepts
Chapter 4. Routing
203
Summary of Contents for NetDefend DFL-1660
Page 28: ...1 3 NetDefendOS State Engine Packet Flow Chapter 1 NetDefendOS Overview 28 ...
Page 88: ...2 6 3 Restore to Factory Defaults Chapter 2 Management and Maintenance 88 ...
Page 166: ...3 10 DNS Chapter 3 Fundamentals 166 ...
Page 254: ...4 7 5 Advanced Settings for Transparent Mode Chapter 4 Routing 254 ...
Page 268: ...5 4 IP Pools Chapter 5 DHCP Services 268 ...
Page 368: ...6 7 Blacklisting Hosts and Networks Chapter 6 Security Mechanisms 368 ...
Page 390: ...7 4 7 SAT and FwdFast Rules Chapter 7 Address Translation 390 ...
Page 414: ...8 3 Customizing Authentication HTML Pages Chapter 8 User Authentication 414 ...
Page 490: ...9 8 6 Specific Symptoms Chapter 9 VPN 490 ...
Page 528: ...10 4 6 Setting Up SLB_SAT Rules Chapter 10 Traffic Management 528 ...
Page 544: ...11 7 HA Advanced Settings Chapter 11 High Availability 544 ...
Page 551: ...12 3 5 Limitations Chapter 12 ZoneDefense 551 ...
Page 574: ...Default 512 13 9 Miscellaneous Settings Chapter 13 Advanced Settings 574 ...
Page 575: ...13 9 Miscellaneous Settings Chapter 13 Advanced Settings 575 ...