GNU Free Documentation License . .

OSPF

: ,
OSPF
:

Open Shortest Path First
( OSI):

:

TCP/IP
:

1988 .
/ID:

89/IP
:

:

RFC 2328
():

GNU Zebra, Quagga, Cisco IOS
():

GNU Zebra, Quagga, Cisco IOS

OSPF (. Open Shortest Path First)  , (link-state technology) (Dijkstras algorithm).

OSPF IETF 1988 . RFC 2328. OSPF (Interior Gateway Protocol  IGP). OSPF .

OSPF :

  • - ;
  • (VLSM);
  • (. . );

[] OSPF

  • (interface)  . OSPF (link) .
  • (link-state advertisement, LSA)  , .
  • (link state)  ; LSA.
  • (metric)  «» ;
  • (autonomous system)  .
  • (area)  , .
  • (neighbours)  , .
  • (adjacency)  .
  • Hello- (hello protocol)  .
  • (neighbours database)  .
  • (link state database, LSDB)  . (topological database), .
  • (router ID, RID)  32- , .

[]

  1. hello- , OSPF. , , , , hello-.
  2. . , hello-, , hello-. OSPF . , , .
  3. , .
  4. , , .
  5. OSPF-, .
  6. , « » , .   .
  7. .

[] , OSPF

[] (DR) (BDR)

. , LSA. , , n, n(n-1)/2 . n-1 LSA , LSA , n² LSA.

LSA (DR) (BDR).

(designated router, DR)  LSA . DR. DR , , DR , .

DR , DR. , DR, . BDR.

(backup designated router, BDR). DR, BDR. DR BDR . DR, BDR DR . BDR, .

, DR BDR , DR (BDR) . DR (BDR) , .

[]

  • HelloInterval  hello- . - , , 10 . 30 .
  • RouterDeadInterval  «». HelloInterval. , RouterDeadInterval 4 hello-, 40 .
  • Wait Timer  DR . RouterDeadInterval.
  • RxmtInterval  (, Database Description Link State Request ). Retransmit interval. 5 .

[]

(internal router)  , . .

(area border router, ABR)  . . .

(backbone router)  . , . , .

(AS boundary router, ASBR)  . , .

[] (LSA)

Type 1 LSA  Router LSA  . LSA . LSA (cost) . .

Type 2 LSA  Network LSA  . DR . LSA , DR. .

Type 3 LSA  Network Summary LSA  . . . .

Network Summary LSA . LSA . .

Type 4 LSA  ASBR Summary LSA  . . ASBR Summary LSA Network Summary LSA , , .

Type 5 LSA  AS External LSA  . . OSPF (default route) OSPF.

Type 6 LSA  Multicast OSPF LSA  LSA, OSPF (Not implemented by CISCO).

Type 7 LSA  AS External LSA for NSSA  NSSA . NSSA . type 7 LSA type 5 LSA.

Type 8 LSA  Link LSA  link-local () (link). . (link).

[]

, .

:

  • OSPF

(area ID). IP-. IP- IP-.

:

[] (backbone area)

( 0.0.0.0) OSPF. , . . , ; .

[] (standard area)

, . , .

[] (stub area)

, . , . ASBR.   ABR ASBR.

[] Totally stubby area

Totally stubby area . , .

[] Not-so-stubby area (NSSA)

NSSA LSA  LSA type 7. NSSA ASBR.

[] OSPF-

OSPF- IP-. « » IP- OSPF 89.

      0               1               2               3
      0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |   version     |     type      |         packet length         |
     +---------------+---------------+-------------------------------+
     |                          router ID                            |
     +---------------------------------------------------------------+
     |                           area ID                             |
     +-------------------------------+-------------------------------+
     |           checksum            |      authentication type      |
     +-------------------------------+-------------------------------+
     |                       authentication                          |
     +---------------------------------------------------------------+
     |                       authentication                          |
     +---------------------------------------------------------------+
  • version  OSPF. OSPF IPv4  2.
  • type  OSPF-. RFC 2328 5 .
  • packet length  , .
  • router ID    32- ,

.

  • area ID  32- .
  • checksum  . , .
  • authentication type  . :
    • 0 
    • 1 
    • 2  MD5-
  • authentication  .

[] Hello-

Hello- (Type 1) OSPF-.

      0               1               2               3
      0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |   version     |     type      |         packet length         |
     +---------------+---------------+-------------------------------+
     |                          router ID                            |
     +---------------------------------------------------------------+
     |                           area ID                             |
     +-------------------------------+-------------------------------+
     |           checksum            |      authentication type      |
     +-------------------------------+-------------------------------+
     |                       authentication                          |
     +---------------------------------------------------------------+
     |                       authentication                          |
     +---------------------------------------------------------------+
     |                        network mask                           |
     +-------------------------------+---------------+---------------+
     |        hello interval         |    options    |router priority|
     +-------------------------------+---------------+---------------+
     |                     router dead interval                      |
     +---------------------------------------------------------------+
     |                      designated router                        |
     +---------------------------------------------------------------+
     |                   backup designated router                    |
     +---------------------------------------------------------------+
     |                          neighbor ID                          |
     +---------------------------------------------------------------+
     |                          neighbor ID                          |
     +---------------------------------------------------------------+
     |                             ...                               |

hello-.

  • network mask  , hello-.
  • hello interval  hello- . LAN 10 .
  • options  8- . .
  • router priority    8- , DR (. Designated router) BDR (. Backup designated router).
  • router dead interval  , .
  • designated router (DR)  IP- DR.
  • backup designated router (BDR)  IP- BDR.
  • neighbor ID  . , hello- , router dead interval.

[] OSPF

[] OSPF 1

[] OSPF 2

IPv4

[] OSPF 3

IPv6

[]

, , IP- , . , .[1]

, .

[]

[]

  1. . . , . . , , « IP-», PACS 02.10.Ox, , № 2, 2008.

[]


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