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1.NBMA环境下的OSPF邻居、路由、数据通信
ospf 1
peer 10.1.1.4 //指定邻居的接口地址，而不是RID
peer 10.1.1.5
area 0.0.0.0
interface Serial1/0/0
link-protocol fr
ip address 10.1.1.1 255.255.255.0
ospf enable 1 area 0.0.0.0
2.OSPF的邻居/邻接关系拍错（troubleshooing）
dis ospf error //多次使用该命令来判断问题
A.相邻设备的RID不能有邻居状态的
<R3>
Jun 5 2018 19:32:52-08:00 R3 %%01OSPF/4/CONFLICT_ROUTERID_INTF(l)[2]:OSPF Router id conflict is detected on interface. (ProcessId=256, RouterId=4.4.0.0, AreaId=34.0.0.0, InterfaceName=Serial2/0/0, IpAddr=3.34.1.10, PacketSrcIp=4.34.1.10) //在s2/0/0接口上检测到了RID冲突
<R3>dis ospf error
OSPF Process 1 with Router ID 0.0.4.4
OSPF error statistics
General packet errors:
0 : IP: received my own packet 0 : Bad packet
0 : Bad version 0 : Bad checksum
0 : Bad area id 0 : Drop on unnumbered interface
0 : Bad virtual link 0 : Bad authentication type
0 : Bad authentication key 0 : Packet too small
0 : Packet size > ip length 0 : Transmit error
0 : Interface down 0 : Unknown neighbor
0 : Bad net segment 0 : Extern option mismatch
33 : Router id confusion //表明RID冲突
补充一点：同一区域的不相邻设备RID冲突，缺少路由
<SW1>dis cu conf ospf
#
ospf 1 router-id 0.0.4.4
area 0.0.0.34
#
interface Vlanif30
ip address 10.1.30.10 255.255.255.0
ospf enable 1 area 0.0.0.34
解决方案：整个AS内部RID保持唯一
[SW1]ospf router-id 10.10.10.10
Info: The configuration succeeded. You need to restart the OSPF process to validate the new router ID.
[SW1-ospf-1]
<SW1>reset ospf process
Warning: The OSPF process will be reset. Continue? [Y/N]:y
B、链路上区域ID不匹配
[R3]dis ospf error
OSPF Process 1 with Router ID 33.1.1.1
OSPF error statistics
General packet errors:
0 : IP: received my own packet 0 : Bad packet
0 : Bad version 0 : Bad checksum
4 : Bad area id 0 : Drop on unnumbered interface
0 : Bad virtual link 0 : Bad authentication type
0 : Bad authentication key 0 : Packet too small
0 : Packet size > ip length 0 : Transmit error
1 : Interface down 0 : Unknown neighbor
0 : Bad net segment 0 : Extern option mismatch
0 : Router id confusion
C、Hello和死亡时间都需要匹配
什么场景下会修改时间呢？在没有其他检测机制的前提下（BFD），协议本身为了加速检测邻居时间和收敛时间
interface Serial2/0/0
link-protocol ppp
ip address 10.1.34.4 255.255.255.0
ospf timer hello 1
ospf timer dead 2
ospf enable 1 area 0.0.0.34
[R3]dis ospf error
OSPF Process 1 with Router ID 33.1.1.1
OSPF error statistics
General packet errors:
0 : IP: received my own packet 303 : Bad packet
0 : Bad version 0 : Bad checksum
38 : Bad area id 0 : Drop on unnumbered interface
0 : Bad virtual link 0 : Bad authentication type
0 : Bad authentication key 0 : Packet too small
0 : Packet size > ip length 0 : Transmit error
1 : Interface down 0 : Unknown neighbor
0 : Bad net segment 0 : Extern option mismatch
0 : Router id confusion
HELLO packet errors:
0 : Netmask mismatch 303 : Hello timer mismatch //先检测Hello，死亡时间暂时不关心
0 : Dead timer mismatch 0 : Virtual neighbor unknown
0 : NBMA neighbor unknown 0 : Invalid Source Address
[R3]dis cu int s2/0/0
[V200R003C00]
#
interface Serial2/0/0
link-protocol ppp
ip address 10.1.34.3 255.255.255.0
ospf timer hello 1 //Hello相同，但死亡时间依旧mismatch
ospf enable 1 area 0.0.0.34
[R3]dis ospf error
OSPF Process 1 with Router ID 33.1.1.1
OSPF error statistics
General packet errors:
0 : IP: received my own packet 453 : Bad packet
0 : Bad version 0 : Bad checksum
38 : Bad area id 0 : Drop on unnumbered interface
0 : Bad virtual link 0 : Bad authentication type
0 : Bad authentication key 0 : Packet too small
0 : Packet size > ip length 0 : Transmit error
1 : Interface down 0 : Unknown neighbor
0 : Bad net segment 0 : Extern option mismatch
0 : Router id confusion
HELLO packet errors:
0 : Netmask mismatch 350 : Hello timer mismatch
103 : Dead timer mismatch 0 : Virtual neighbor unknown
0 : NBMA neighbor unknown 0 : Invalid Source Address
[R3-Serial2/0/0]ospf timer dead 1
Error: The dead interval must be greater than the hello interval. //华为设备不能把死亡时间配置的小于等于hello时间！
D、多点接入网络的掩码一致（2类LSA）
[SW1-Vlanif30]ip address 10.1.30.10 28
[SW1-Vlanif30]ping 10.1.30.3
PING 10.1.30.3: 56 data bytes, press CTRL_C to break
Reply from 10.1.30.3: bytes=56 Sequence=1 ttl=255 time=70 ms
Reply from 10.1.30.3: bytes=56 Sequence=2 ttl=255 time=40 ms
dis ospf error
HELLO packet errors:
26 : Netmask mismatch 0 : Hello timer mismatch
0 : Dead timer mismatch 0 : Virtual neighbor unknown
0 : NBMA neighbor unknown 0 : Invalid Source Address
多点接入网络不一致：
[SW1-Vlanif30]dis ospf error
OSPF Process 1 with Router ID 10.10.10.10
OSPF error statistics
General packet errors:
0 : IP: received my own packet 56 : Bad packet
0 : Bad version 0 : Bad checksum
0 : Bad area id 0 : Drop on unnumbered interface
0 : Bad virtual link 0 : Bad authentication type
0 : Bad authentication key 0 : Packet too small
0 : Packet size > ip length 0 : Transmit error
6 : Interface down 0 : Unknown neighbor
24 : Bad net segment //错误的网段
点到点网络不受掩码的影响（Hello中掩码位会显示0.0.0.0即不检测）：
[R3-Serial2/0/0]ip address 10.1.34.2 28
[R3-Serial2/0/0]dis ospf peer bri
OSPF Process 1 with Router ID 33.1.1.1
Peer Statistic Information
----------------------------------------------------------------------------
Area Id Interface Neighbor id State
0.0.0.34 GigabitEthernet0/0/1 10.10.10.10 Full
0.0.0.34 Serial2/0/0 0.0.4.4 Full
请问点到点网络建立OSPF邻居受子网影响么？在点到点的OSPF网络，掩码、子网并不要求，可以完成邻居关系
请问如果一个接口没有配置IP地址可以建立邻居么？
[R4-Serial2/0/0]ip address unnumbered interface LoopBack 0 //串口借用环回接口的地址作为源发送报文，通常会用到广域网IP地址匮乏的环境中
E、MTU一致性检测
默认情况下华为设备上不检测MTU一致性，除非2段都配置
ospf mtu-enable
[SW1-Vlanif30]dis th
#
interface Vlanif30
ip address 10.1.30.10 255.255.255.0
ospf mtu-enable
ospf enable 1 area 0.0.0.34
[R3]dis cu int g0/0/1
[V200R003C00]
#
interface GigabitEthernet0/0/1
mtu 1504
ip address 10.1.30.4 255.255.255.0
ospf mtu-enable
ospf enable 1 area 0.0.0.34
[R3]dis ospf peer brief
OSPF Process 1 with Router ID 33.1.1.1
Peer Statistic Information
----------------------------------------------------------------------------
Area Id Interface Neighbor id State
0.0.0.34 GigabitEthernet0/0/1 10.10.10.10 ExStart
0.0.0.34 Serial2/0/0 0.0.4.4 Full
会卡到exstart/exchange状态，注意并不是2-way
dis ospf error
DD packet errors:
0 : Neighbor state low 0 : Unknown LSA type
2 : MTU option mismatch
F、标志位的一致性
E=1代表可以接受外部路由，E=0
NP，和NSSA特殊区域有关
3.OSPF的邻接/OSPF的网络类型
有邻居但是缺少路由条目：1）DR/BDR引发的 2）同一区域的不相邻设备RID冲突 3）网络类型问题
物理介质封装类型：
以太网
帧中继（ATM）
PPP/HDLC
用命令验证：
[R3-Serial2/0/0]link-protocol ?
fr Select FR as line protocol
hdlc Enable HDLC protocol
lapb LAPB(X.25 level 2 protocol)
ppp Point-to-Point protocol
sdlc SDLC(Synchronous Data Line Control) protocol
x25 X.25 protocol
OSPF的网络类型（为了适应不同的介质的封装类型），5种
[R3-Serial2/0/0]ospf network-type ?
broadcast Specify OSPF broadcast network //广播
nbma Specify OSPF NBMA network //非广播多路访问
p2mp Specify OSPF point-to-multipoint network //点到多点
p2p Specify OSPF point-to-point network //点到点
==========================
作业：请验证OSPF的4种错误的邻居关系，用dis ospf error去摸排错误
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发表于 2022-8-8 18:48:58
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