OSPFのEXSTART状態

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前の投稿 - 次の投稿 | 親投稿 - 子投稿.1 .2 | 投稿日時 2014-10-28 15:53
Elixirff11  常連   投稿数: 13
隣接関係を持つ2代のルータ間で、最初に交信を始める方をマスターと呼び、
マスターの選出は、ルータIDの大きい方とあります。
一方DR・BDRの選出の優先順位はプライオリティ→ルータIDです。

ここでルータIDは小さいが、プライオリティが大きいためDRに
選出された場合、DRではあるが、マスターになれないという
ことは発生するのでしょうか?

FULL状態になるための一時的な役割なので逆転しても
問題はないですよね?

ping-tの問題で類似のものがあれば申し訳ないです。
久しぶりに勉強して気になったもので、質問しています。
前の投稿 - 次の投稿 | 親投稿 - 子投稿なし | 投稿日時 2014-10-28 21:55
antares01  長老   投稿数: 690
引用:
ここでルータIDは小さいが、プライオリティが大きいためDRに
選出された場合、DRではあるが、マスターになれないという
ことは発生するのでしょうか?

マスタにはなれません。マスタ/スレイブはルータIDを見ています。
双方が初めはマスタになるつもりでDDパケットを交換しますが、
ルータIDの小さいほうは途中でマスタを諦めて、スレイブになります。
長くて申し訳ないですがログも貼っておきます。最後のほうの★のところをみてください。
R1 router-id 1.1.1.1、priority 5
R2 router-id 2.2.2.2、priority 1
(R1、R2の順にほぼ同時にclear ip ospf processしています)

--------------------
R1#show ip ospf int
FastEthernet0/0 is up, line protocol is up
Internet Address 10.0.0.1/30, Area 0
Process ID 1, Router ID 1.1.1.1, Network Type BROADCAST, Cost: 1
Transmit Delay is 1 sec, State DR, Priority 5
Designated Router (ID) 1.1.1.1, Interface address 10.0.0.1
Backup Designated router (ID) 2.2.2.2, Interface address 10.0.0.2
Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5
oob-resync timeout 40
Hello due in 00:00:07
Supports Link-local Signaling (LLS)
Index 1/1, flood queue length 0
Next 0x0(0)/0x0(0)
Last flood scan length is 0, maximum is 2
Last flood scan time is 0 msec, maximum is 4 msec
Neighbor Count is 1, Adjacent neighbor count is 1
Adjacent with neighbor 2.2.2.2 (Backup Designated Router)
Suppress hello for 0 neighbor(s)
R1#clear ip ospf process
Reset ALL OSPF processes? [no]: yes
R1#
*Mar 1 00:30:17.623: OSPF: Interface FastEthernet0/0 going Down
*Mar 1 00:30:17.623: OSPF: 2.2.2.2 address 10.0.0.2 on FastEthernet0/0 is dead, state DOWN
*Mar 1 00:30:17.623: %OSPF-5-ADJCHG: Process 1, Nbr 2.2.2.2 on FastEthernet0/0 from FULL to DOWN, Neighbor Down: Interface down or detached
*Mar 1 00:30:17.627: OSPF: Neighbor change Event on interface FastEthernet0/0
*Mar 1 00:30:17.627: OSPF: DR/BDR election on FastEthernet0/0
*Mar 1 00:30:17.627: OSPF: Elect BDR 0.0.0.0
*Mar 1 00:30:17.627: OSPF: Elect DR 1.1.1.1
*Mar 1 00:30:17.627: DR: 1.1.1.1 (Id) BDR: none
*Mar 1 00:30:17.627: OSPF: 1.1.1.1 address 10.0.0.1 on FastEthernet0/0 is dead, state DOWN
*Mar 1 00:30:17.627: OSPF: Neighbor change Event on interface FastEthernet0/0
*Mar 1 00:30:17.627: OSPF: DR/BDR election on FastEthernet0/0
*Mar 1 00:30:17.627: OSPF: Elect BDR 0.0.0.0
*Mar 1 00:30:17.627: OSPF: Elect DR 0.0.0.0
*Mar 1 00:30:17.627: OSPF: Elect BDR 0.0.0.0
*Mar 1 00:30:17.627: OSPF: Elect DR 0.0.0.0
*Mar 1 00:30:17.627: DR: none BDR: none
*Mar 1 00:30:17.627: OSPF: Flush network LSA immediately
*Mar 1 00:30:17.627: OSPF: Remember old DR 1.1.1.1 (id)
*Mar 1 00:30:17.627: OSPF: Interface FastEthernet0/0 going Up
*Mar 1 00:30:17.651: OSPF: 2 Way Communication to 2.2.2.2 on FastEthernet0/0, state 2WAY
*Mar 1 00:30:17.651: OSPF: Backup seen Event before WAIT timer on FastEthernet0/0
*Mar 1 00:30:17.651: OSPF: DR/BDR election on FastEthernet0/0
*Mar 1 00:30:17.651: OSPF: Elect BDR 1.1.1.1
*Mar 1 00:30:17.651: OSPF: Elect DR 2.2.2.2
*Mar 1 00:30:17.655: OSPF: Elect BDR 1.1.1.1
*Mar 1 00:30:17.655: OSPF: Elect DR 2.2.2.2
*Mar 1 00:30:17.655: DR: 2.2.2.2 (Id) BDR: 1.1.1.1 (Id)
*Mar 1 00:30:17.655: OSPF: Send DBD to 2.2.2.2 on FastEthernet0/0 seq 0x1FF6 opt 0x52 flag 0x7 len 32
*Mar 1 00:30:17.679: OSPF: Rcv DBD from 2.2.2.2 on FastEthernet0/0 seq 0x25B0 opt 0x52 flag 0x7 len 32 mtu 1500 state EXSTART
*Mar 1 00:30:17.679: OSPF: NBR Negotiation Done. We are the SLAVE
*Mar 1 00:30:17.683: OSPF: Send DBD to 2.2.2.2 on FastEthernet0/0 seq 0x25B0 opt 0x52 flag 0x0 len 32
*Mar 1 00:30:17.699: OSPF: Rcv DBD from 2.2.2.2 on FastEthernet0/0 seq 0x25B1 opt 0x52 flag 0x3 len 52 mtu 1500 state EXCHANGE
*Mar 1 00:30:17.699: OSPF: Send DBD to 2.2.2.2 on FastEthernet0/0 seq 0x25B1 opt 0x52 flag 0x0 len 32
*Mar 1 00:30:17.711: OSPF: Rcv DBD from 2.2.2.2 on FastEthernet0/0 seq 0x25B2 opt 0x52 flag 0x1 len 32 mtu 1500 state EXCHANGE
*Mar 1 00:30:17.711: OSPF: Exchange Done with 2.2.2.2 on FastEthernet0/0
*Mar 1 00:30:17.711: OSPF: Send LS REQ to 2.2.2.2 length 12 LSA count 1
*Mar 1 00:30:17.711: OSPF: Send DBD to 2.2.2.2 on FastEthernet0/0 seq 0x25B2 opt 0x52 flag 0x0 len 32
*Mar 1 00:30:17.731: OSPF: Rcv LS UPD from 2.2.2.2 on FastEthernet0/0 length 64 LSA count 1
*Mar 1 00:30:17.731: OSPF: Synchronized with 2.2.2.2 on FastEthernet0/0, state FULL
*Mar 1 00:30:17.731: %OSPF-5-ADJCHG: Process 1, Nbr 2.2.2.2 on FastEthernet0/0 from LOADING to FULL, Loading Done
*Mar 1 00:30:18.039: OSPF: Rcv LS UPD from 2.2.2.2 on FastEthernet0/0 length 64 LSA count 1
*Mar 1 00:30:18.055: OSPF: Cannot see ourself in hello from 2.2.2.2 on FastEthernet0/0, state INIT
*Mar 1 00:30:18.059: OSPF: Neighbor change Event on interface FastEthernet0/0
*Mar 1 00:30:18.059: OSPF: DR/BDR election on FastEthernet0/0
*Mar 1 00:30:18.059: OSPF: Elect BDR 1.1.1.1
*Mar 1 00:30:18.059: OSPF: Elect DR 1.1.1.1
*Mar 1 00:30:18.059: OSPF: Elect BDR 0.0.0.0
*Mar 1 00:30:18.059: OSPF: Elect DR 1.1.1.1
*Mar 1 00:30:18.063: DR: 1.1.1.1 (Id) BDR: none
*Mar 1 00:30:18.063: OSPF: Remember old DR 2.2.2.2 (id)
*Mar 1 00:30:18.127: OSPF: Reset old DR on FastEthernet0/0
*Mar 1 00:30:18.127: OSPF: Build router LSA for area 0, router ID 1.1.1.1, seq 0x80000001
*Mar 1 00:30:18.127: OSPF: No full nbrs to build Net Lsa for interface FastEthernet0/0
*Mar 1 00:30:27.639: OSPF: 2 Way Communication to 2.2.2.2 on FastEthernet0/0, state 2WAY
*Mar 1 00:30:27.639: OSPF: Neighbor change Event on interface FastEthernet0/0
*Mar 1 00:30:27.643: OSPF: DR/BDR election on FastEthernet0/0
*Mar 1 00:30:27.643: OSPF: Elect BDR 2.2.2.2
*Mar 1 00:30:27.643: OSPF: Elect DR 1.1.1.1
*Mar 1 00:30:27.643: DR: 1.1.1.1 (Id) BDR: 2.2.2.2 (Id)
*Mar 1 00:30:27.643: OSPF: Send DBD to 2.2.2.2 on FastEthernet0/0 seq 0x1C5 opt 0x52 flag 0x7 len 32
*Mar 1 00:30:27.647: OSPF: Neighbor change Event on interface FastEthernet0/0
*Mar 1 00:30:27.647: OSPF: DR/BDR election on FastEthernet0/0
*Mar 1 00:30:27.647: OSPF: Elect BDR 2.2.2.2
*Mar 1 00:30:27.647: OSPF: Elect DR 1.1.1.1
*Mar 1 00:30:27.647: DR: 1.1.1.1 (Id) BDR: 2.2.2.2 (Id)
*Mar 1 00:30:27.651: OSPF: Neighbor change Event on interface FastEthernet0/0
*Mar 1 00:30:27.651: OSPF: DR/BDR election on FastEthernet0/0
*Mar 1 00:30:27.651: OSPF: Elect BDR 2.2.2.2
*Mar 1 00:30:27.651: OSPF: Elect DR 1.1.1.1
*Mar 1 00:30:27.651: DR: 1.1.1.1 (Id) BDR: 2.2.2.2 (Id) ★
*Mar 1 00:30:27.655: OSPF: Rcv DBD from 2.2.2.2 on FastEthernet0/0 seq 0x18CC opt 0x52 flag 0x7 len 32 mtu 1500 state EXSTART
*Mar 1 00:30:27.655: OSPF: NBR Negotiation Done. We are the SLAVE ★
*Mar 1 00:30:27.655: OSPF: Send DBD to 2.2.2.2 on FastEthernet0/0 seq 0x18CC opt 0x52 flag 0x2 len 52
*Mar 1 00:30:27.699: OSPF: Rcv DBD from 2.2.2.2 on FastEthernet0/0 seq 0x18CD opt 0x52 flag 0x3 len 52 mtu 1500 state EXCHANGE
前の投稿 - 次の投稿 | 親投稿 - 子投稿なし | 投稿日時 2014-10-29 8:36
Elixirff11  常連   投稿数: 13
ちょっとした疑問に、実際のログまで貼り付けていただき、
ありがとうございます。おかげさまですっきりいたしました。

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