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OSPF邻居状态机Attempt的问题

发布日期:2012-08-17 09:24:26

IP路由协议疑难解析:
Attempt:对NBMA网络上的邻居是有效的。如果一个邻居处于这种状 态,则表示从它的邻居没有收到任何信息,但是它做出了认真的努力来与邻居联系。认真的努力(serious effort)意思是这个路由器将不断地每隔一个Hello间隙就发送一个Hello分组来与邻居联系。
卷一:
Down -- The initial state of a neighbor conversation indicates that no Hellos have been heard from the neighbor in the last RouterDeadInterval. Hellos are not sent to down neighbor unless those neighbors are on NBMA networks; in this case, Hellos are sent every PollInterval. If a neighbor transitions to the Down state from higher state, the link state Retransmission, Database, and Link State Request lists are cleard.
Attempt -- This state applies only to neighbors on NBMA networks, where neighbors are manually configured. A DR-eligible router transitions a neighbor to the Attempt state when the interface to the neighbor first becomes Active or when the router is the DR or BDR. A router sends packets to a neighbor in Attempt state at the HelloInterval instead of the PollInterval.

A DR-eligible router transitions a neighbor to the Attempt state when the interface to the neighbor first becomes Active or when the router is the DR or BDR. 这句话看不明白,感觉卷一和IP路由协议疑难解析这个问题上的说法有矛盾,还是理解不了。
Attempt是Down到Init的过度阶段,这样理解对吗?那一定到达Attempt状态吗?到达Attempt状态 的条件是什么?

我小做了个实验,R1---R2串行连接,接口指定ip ospf network nonbroadcast,然后R1手动指定邻居,R2不指定。R1开始向R2发送hello,120秒后R1选自己为DR。
然后在R2上指定邻居,然后到达2-way状态。
接下来显示一直在重传DBD www.it165.net
*Mar 1 00:12:09.703: OSPF: Send DBD to 2.2.2.2 on Serial0 seq 0x822 opt 0x52 flag 0x7 len 32
*Mar 1 00:12:09.703: OSPF: Retransmitting DBD to 2.2.2.2 on Serial0 [17]
一直传了17遍才Loading to Full

大概过了120秒后,显示:
*Mar 1 00:20:12.171: %OSPF-5-ADJCHG: Process 1, Nbr 2.2.2.2 on Serial0 from FULL to DOWN, Neighbor Down: Too many retransmissions
*Mar 1 00:21:12.175: %OSPF-5-ADJCHG: Process 1, Nbr 0.0.0.0 on Serial0 from ATTEMPT to DOWN, Neighbor Down: Ignore timer expired
邻居状态:
Neighbor ID     Pri   State           Dead Time   Address         Interface
N/A               1   ATTEMPT/DROTHER    -        192.168.12.2    Serial0

再过了60秒后,显示:
*Mar 1 00:27:13.583: %OSPF-5-ADJCHG: Process 1, Nbr 0.0.0.0 on Serial0 from ATTEMPT to DOWN, Neighbor Down: Ignore timer expired
*Mar 1 00:27:13.783: %OSPF-5-ADJCHG: Process 1, Nbr 2.2.2.2 on Serial0 from LOADING to FULL, Loading Done
邻居状态:
Neighbor ID     Pri   State           Dead Time   Address         Interface
2.2.2.2           1   FULL/BDR        00:01:56    192.168.12.2    Serial0

然后一直这样循环,Attempt倒是弄明白了,这些情况又是怎么回事……

Attempt状态说简单就是由于出现Attempt状态的路由器的邻居不回应hello造成的

Tag标签: OSPF   邻居状态机   Attempt  
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