34
OSPF C
ONFIGURATION
OSPF Overview
Introduction to OSPF
Open shortest path first (OSPF) is a link state-based interior gateway protocol
developed by IETF. At present, OSPF version 2 (RFC 2328) is used, which has the
following features:
■
High applicability: OSPF supports networks of various sizes and can support up
to several hundred routers.
■
Fast convergence: OSPF can transmit update packets immediately after the
network topology changes so that the change can be synchronized in the
autonomous system (AS).
■
Loop-free: Since OSPF calculates routes with the shortest path tree algorithm
according to the collected link states, it guarantees that no loop routes will be
generated from the algorithm basis.
■
Area partition: OSPF allows an autonomous system network to be divided into
different areas for convenient management so that routing information
transmitted between the areas is abstracted further, thereby reducing network
bandwidth consumption.
■
Equivalent route: OSPF supports multiple equivalent routes to the same
destination.
■
Routing hierarchy: OSPF has a four-level routing hierarchy. It prioritizes the
routes as intra-area, inter-area, external type-1, and external type-2 routes.
■
Authentication: OSPF supports interface-based packet authentication to
guarantee the security of route calculation.
■
Multicast transmission: OSPF supports transmitting protocol packets in
multicast mode.
OSPF Route Calculation
Taking no account of area partition, the routing calculation process of the OSPF
protocol is as follows:
■
Each OSPF-capable router maintains a link state database (LSDB), which
describes the topology of the whole AS. According to the network topology
around itself, each router generates a link state advertisement (LSA). Routers
on the network exchange LSAs with each other by transmitting protocol
packets. Thus, each router receives the LSAs of other routers and all these LSAs
form the LSDB of the router.
■
An LSA describes the network topology around a router, whereas an LSDB
describes the network topology of the whole network. Routers can easily
transform the LSDB to a weighted directed map, which actually reflects the
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Страница 32: ...32 CHAPTER 1 CLI OVERVIEW ...
Страница 70: ...70 CHAPTER 5 LOGGING IN USING MODEM ...
Страница 76: ...76 CHAPTER 7 LOGGING IN THROUGH NMS ...
Страница 86: ...86 CHAPTER 9 CONFIGURATION FILE MANAGEMENT ...
Страница 120: ...120 CHAPTER 13 ISOLATE USER VLAN CONFIGURATION ...
Страница 126: ...126 CHAPTER 14 SUPER VLAN ...
Страница 136: ...136 CHAPTER 16 IP PERFORMANCE CONFIGURATION ...
Страница 152: ...152 CHAPTER 17 IPX CONFIGURATION ...
Страница 164: ...164 CHAPTER 19 QINQ CONFIGURATION ...
Страница 172: ...172 CHAPTER 21 SHARED VLAN CONFIGURATION ...
Страница 182: ...182 CHAPTER 22 PORT BASIC CONFIGURATION ...
Страница 198: ...198 CHAPTER 24 PORT ISOLATION CONFIGURATION ...
Страница 208: ...208 CHAPTER 25 PORT SECURITY CONFIGURATION ...
Страница 224: ...224 CHAPTER 27 DLDP CONFIGURATION ...
Страница 232: ...232 CHAPTER 28 MAC ADDRESS TABLE MANAGEMENT ...
Страница 240: ...240 CHAPTER 29 CENTRALIZED MAC ADDRESS AUTHENTICATION CONFIGURATION ...
Страница 280: ...280 CHAPTER 30 MSTP CONFIGURATION ...
Страница 348: ...348 CHAPTER 35 IS IS CONFIGURATION ...
Страница 408: ...408 CHAPTER 39 802 1X CONFIGURATION ...
Страница 412: ...412 CHAPTER 40 HABP CONFIGURATION ...
Страница 422: ...422 CHAPTER 41 MULTICAST OVERVIEW ...
Страница 426: ...426 CHAPTER 42 GMRP CONFIGURATION ...
Страница 480: ...480 CHAPTER 47 PIM CONFIGURATION ...
Страница 506: ...506 CHAPTER 48 MSDP CONFIGURATION ...
Страница 552: ...552 CHAPTER 51 TRAFFIC ACCOUNTING CONFIGURATION ...
Страница 570: ...570 CHAPTER 53 HA CONFIGURATION ...
Страница 582: ...582 CHAPTER 54 ARP CONFIGURATION SwitchA arp protective down recover interval 200 ...
Страница 622: ...622 CHAPTER 58 DHCP RELAY AGENT CONFIGURATION ...
Страница 684: ...684 CHAPTER 61 QOS CONFIGURATION ...
Страница 718: ...718 CHAPTER 63 CLUSTER ...
Страница 738: ...738 CHAPTER 67 UDP HELPER CONFIGURATION ...
Страница 752: ...752 CHAPTER 69 RMON CONFIGURATION ...
Страница 772: ...772 CHAPTER 70 NTP CONFIGURATION ...
Страница 796: ...796 CHAPTER 72 FILE SYSTEM MANAGEMENT ...
Страница 802: ...802 CHAPTER 73 BIMS CONFIGURATION ...
Страница 814: ...814 CHAPTER 74 FTP AND TFTP CONFIGURATION ...
Страница 830: ...830 CHAPTER 75 INFORMATION CENTER ...
Страница 836: ...836 CHAPTER 76 DNS CONFIGURATION ...
Страница 852: ...852 CHAPTER 77 BOOTROM AND HOST SOFTWARE LOADING ...
Страница 858: ...858 CHAPTER 78 BASIC SYSTEM CONFIGURATION DEBUGGING ...