Chapter 13 Routing Protocols
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Each type of area is illustrated in the following figure.
Figure 154
OSPF: Types of Areas
This OSPF AS consists of four areas, areas 0-3. Area 0 is always the backbone. In
this example, areas 1, 2, and 3 are all connected to it. Area 1 is a normal area. It
has routing information about the OSPF AS and networks X and Y. Area 2 is a stub
area. It has routing information about the OSPF AS, but it depends on a default
route to send information to networks X and Y. Area 3 is a NSSA. It has routing
information about the OSPF AS and network Y but not about network X.
OSPF Routers
Every router in the same area has the same routing information. They do this by
exchanging Hello messages to confirm which neighbor (layer-3) devices exist, and
then they exchange database descriptions (DDs) to create a synchronized link-
state database. The link-state database contains records of router IDs, their
associated links and path costs. The link-state database is then constantly
updated through Link State Advertisements (LSA). Each router uses the link state
database and the Dijkstra algorithm to compute the least cost paths to network
destinations.
Like areas, each router has a unique 32-bit ID in the OSPF AS, and there are
several types of routers. Each type is really just a different role, and it is possible
for one router to play multiple roles at one time.
• An internal router (IR) only exchanges routing information with other routers in
the same area.
• An Area Border Router (ABR) connects two or more areas. It is a member of all
the areas to which it is connected, and it filters, summarizes, and exchanges
routing information between them.
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Страница 165: ...Chapter 9 Signature Update ZyWALL USG 2000 User s Guide 165 Figure 120 Successful System Protect Signature Download ...
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Страница 234: ...Chapter 11 Trunks ZyWALL USG 2000 User s Guide 234 ...
Страница 248: ...Chapter 12 Policy and Static Routes ZyWALL USG 2000 User s Guide 248 ...
Страница 272: ...Chapter 15 DDNS ZyWALL USG 2000 User s Guide 272 ...
Страница 287: ...Chapter 16 Virtual Servers ZyWALL USG 2000 User s Guide 287 ...
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Страница 335: ...Chapter 21 IPSec VPN ZyWALL USG 2000 User s Guide 335 Figure 212 VPN IPSec VPN VPN Connection Edit IKE ...
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Страница 392: ...Chapter 23 SSL User Screens ZyWALL USG 2000 User s Guide 392 ...
Страница 394: ...Chapter 24 SSL User Application Screens ZyWALL USG 2000 User s Guide 394 ...
Страница 402: ...Chapter 25 SSL User File Sharing ZyWALL USG 2000 User s Guide 402 ...
Страница 412: ...Chapter 27 L2TP VPN ZyWALL USG 2000 User s Guide 412 ...
Страница 440: ...Chapter 28 L2TP VPN Example ZyWALL USG 2000 User s Guide 440 ...
Страница 441: ...441 PART V Application Patrol Application Patrol 443 ...
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Страница 469: ...469 PART VI Anti X Anti Virus 471 IDP 487 ADP 521 Content Filtering 541 Content Filter Reports 567 Anti Spam 575 ...
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Страница 531: ...Chapter 32 ADP ZyWALL USG 2000 User s Guide 531 Figure 371 Profiles Protocol Anomaly ...
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Страница 686: ...Chapter 43 Certificates ZyWALL USG 2000 User s Guide 686 ...
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Страница 794: ...Chapter 49 Reports ZyWALL USG 2000 User s Guide 794 ...
Страница 796: ...Chapter 50 Diagnostics ZyWALL USG 2000 User s Guide 796 ...
Страница 798: ...Chapter 51 Reboot ZyWALL USG 2000 User s Guide 798 ...
Страница 812: ...Chapter 53 Product Specifications ZyWALL USG 2000 User s Guide 812 ...
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Страница 874: ...Appendix A Log Descriptions ZyWALL USG 2000 User s Guide 874 ...
Страница 956: ...Appendix E Open Software Announcements ZyWALL USG 2000 User s Guide 956 ...
Страница 960: ...Appendix F Legal Information ZyWALL USG 2000 User s Guide 960 ...
Страница 986: ...Index ZyWALL USG 2000 User s Guide 986 ...