OSPF中 LSA 2的真正用法
[align=left][b][font=Verdana][size=12pt]OSPF[/size][/font][/b][b][font=宋体][size=12pt]中[/size][/font][/b][b][font=Verdana][size=12pt]Lsa 2[/size][/font][/b][b][font=宋体][size=12pt]的用法[/size][/font][/b][font=Verdana][size=12pt][/size][/font][/align][align=left][font=Verdana][size=12pt] [/size][/font][/align]
[align=left][font=宋体][size=12pt]概述[/size][/font][font=Verdana][size=12pt]:[/size][/font][font=Verdana][size=9pt][/size][/font][/align]
[align=left][font=Verdana][size=9pt]----------------------------------------------------------------------------------------[/size][/font][/align]
[align=left][font=宋体][size=9pt]此文档在于描述[/size][/font][font=Verdana][size=9pt]OSPF[/size][/font][font=宋体][size=9pt]中[/size][/font][font=Verdana][size=9pt]DR[/size][/font][font=宋体][size=9pt]始发的[/size][/font][font=Verdana][size=9pt]LSA2[/size][/font][font=宋体][size=9pt]在[/size][/font][font=Verdana][size=9pt]SPF[/size][/font][font=宋体][size=9pt]算法中的作用[/size][/font][font=Verdana][size=9pt].[/size][/font][font=Verdana][size=9pt][/size][/font][/align]
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[align=left][font=宋体][size=12pt]拓扑[/size][/font][font=Verdana][size=12pt]:[/align]
[img=473,294]http://www.one-tom.com/bbs/uploads/20070711_025705_lsa2.JPG[/img]
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[align=left][font=Verdana][size=9pt][/size][/font][/align]
[font=宋体][size=12pt]配置[/size][/font][font=Verdana][size=12pt]:[/size][/font][font=Verdana][size=9pt][/size][/font]
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[align=left][font=Verdana][size=9pt]R1[/size][/font][font=宋体][size=9pt]的配置[/size][/font][font=Verdana][size=9pt][/size][/font][/align]
[align=left][font=Verdana][size=9pt] [/size][/font][/align]
[align=left][font=Verdana][size=9pt]R1#show run
Building configuration...
!
hostname R1
!
interface Serial2/0
ip address 13.1.1.1 255.255.255.0
serial restart-delay 0
!
router ospf 10[/size][/font][/align]
[align=left][font=Verdana][size=9pt] router-id 1.1.1.1
log-adjacency-changes
network 13.1.1.1 0.0.0.0 area 0
!
end[/size][/font][/align]
[align=left][font=Verdana][size=9pt]--------------------------------------------------------[/size][/font][/align]
[align=left][font=Verdana][size=9pt]R2[/size][/font][font=宋体][size=9pt]的配置[/size][/font][font=Verdana][size=9pt][/size][/font][/align]
[align=left][font=Verdana][size=9pt] [/size][/font][/align]
[align=left][font=Verdana][size=9pt]R2#show run
Building configuration...
!
hostname R2
!
interface Ethernet0/0
ip address 10.1.1.2 255.255.255.0
!
router ospf 10
router-id 2.2.2.2
log-adjacency-changes
network 10.1.1.2 0.0.0.0 area 0
!
end[/size][/font][/align]
[align=left][font=Verdana][size=9pt]---------------------------------------------------------[/size][/font][/align]
[align=left][font=Verdana][size=9pt]R3[/size][/font][font=宋体][size=9pt]的配置[/size][/font][font=Verdana][size=9pt][/size][/font][/align]
[align=left][font=Verdana][size=9pt] [/size][/font][/align]
[align=left][font=Verdana][size=9pt]R3#show run
Building configuration...
!
hostname R3
!
interface Ethernet0/0
ip address 10.1.1.3 255.255.255.0
!
interface Serial1/0
ip address 13.1.1.3 255.255.255.0
serial restart-delay 0
!
router ospf 10
router-id 3.3.3.3
log-adjacency-changes
network 10.1.1.3 0.0.0.0 area 0
network 13.1.1.3 0.0.0.0 area 0
!
end[/size][/font][/align]
[align=left][font=Verdana][size=9pt]---------------------------------------------------------[/size][/font][/align]
[align=left][font=Verdana][size=9pt]R4[/size][/font][font=宋体][size=9pt]的配置[/size][/font][font=Verdana][size=9pt][/size][/font][/align]
[align=left][font=Verdana][size=9pt] [/size][/font][/align]
[align=left][font=Verdana][size=9pt]R4#show run
Building configuration...
!
hostname R4
!
interface Ethernet0/0
ip address 10.1.1.4 255.255.255.0
!
router ospf 10
router-id 4.4.4.4
log-adjacency-changes
network 10.1.1.4 0.0.0.0 area 0
!
end[/size][/font][/align]
[align=left][font=Verdana][size=9pt]---------------------------------------------------------[/size][/font][/align]
[align=left][font=Verdana][size=9pt]R5[/size][/font][font=宋体][size=9pt]的配置[/size][/font][font=Verdana][size=9pt][/size][/font][/align]
[align=left][font=Verdana][size=9pt] [/size][/font][/align]
[align=left][font=Verdana][size=9pt]R5#show run
Building configuration...[/size][/font][/align]
[align=left][font=Verdana][size=9pt]
hostname R5
!
interface Ethernet0/0
ip address 10.1.1.5 255.255.255.0
!
router ospf 10
router-id 5.5.5.5
log-adjacency-changes
network 10.1.1.5 0.0.0.0 area 0
!
end[/size][/font][/align]
[align=left][font=Verdana][size=9pt]-----------------------------------------------------------[/size][/font][/align]
[align=left][font=宋体][size=12pt]现象[/size][/font][font=Verdana][size=12pt]:[/size][/font][font=Verdana][size=9pt][/size][/font][/align]
[align=left][font=Verdana][size=9pt] [/size][/font][/align]
[align=left][font=Verdana][size=10pt]R3[/size][/font][font=宋体][size=10pt]被选举为[/size][/font][font=Verdana][size=10pt]DR,[/size][/font][font=宋体][size=10pt]先看看作为[/size][/font][font=Verdana][size=10pt]DR[/size][/font][font=宋体][size=10pt]的[/size][/font][font=Verdana][size=10pt]R3[/size][/font][font=宋体][size=10pt]通告给[/size][/font][font=Verdana][size=10pt]R1[/size][/font][font=宋体][size=10pt]的[/size][/font][font=Verdana][size=10pt]LSA1[/size][/font][font=宋体][size=10pt]和[/size][/font][font=Verdana][size=10pt]LSA2[/size][/font][font=Verdana][size=9pt][/size][/font][/align]
[align=left][font=Verdana][size=10pt]-----------------------------------------------------[/size][/font][font=Verdana][size=9pt][/size][/font][/align]
[align=left][font=Verdana][size=10pt]R1#show ip ospf data router adv 3.3.3.3[/size][/font][font=Verdana][size=9pt][/size][/font][/align]
[align=left][font=Verdana][size=10pt] OSPF Router with ID (1.1.1.1) (Process ID 10)[/size][/font][font=Verdana][size=9pt][/size][/font][/align]
[align=left][font=Verdana][size=10pt] Router Link States (Area 0)[/size][/font][font=Verdana][size=9pt][/size][/font][/align]
[align=left][font=Verdana][size=10pt] LS age: 791
Options: (No TOS-capability, DC)
LS Type: Router Links
Link State ID: 3.3.3.3
Advertising Router: 3.3.3.3
LS Seq Number: 80000015
Checksum: 0x5BC0
Length: 60
Number of Links: 3[/size][/font][font=Verdana][size=9pt][/size][/font][/align]
[align=left][font=Verdana][size=10pt] Link connected to: another Router (point-to-point)
(Link ID) Neighboring Router ID: 1.1.1.1
(Link Data) Router Interface address: 13.1.1.3
Number of TOS metrics: 0
TOS 0 Metrics: 64[/size][/font][font=Verdana][size=9pt][/size][/font][/align]
[align=left][font=Verdana][size=10pt] Link connected to: a Stub Network
(Link ID) Network/subnet number: 13.1.1.0
(Link Data) Network Mask: 255.255.255.0
Number of TOS metrics: 0
TOS 0 Metrics: 64[/size][/font][font=Verdana][size=9pt][/size][/font][/align]
[align=left][font=Verdana][size=10pt] Link connected to: a Transit Network
(Link ID) Designated Router address: 10.1.1.3
(Link Data) Router Interface address: 10.1.1.3
Number of TOS metrics: 0
TOS 0 Metrics: 10[/size][/font][font=Verdana][size=9pt][/size][/font][/align]
[align=left][font=Verdana][size=9pt] [/size][/font][/align]
[align=left][font=Verdana][size=10pt]R3[/size][/font][font=宋体][size=10pt]通告给[/size][/font][font=Verdana][size=10pt]R1[/size][/font][font=宋体][size=10pt]的[/size][/font][font=Verdana][size=10pt]LSA1,[/size][/font][font=宋体][size=10pt]里面表现了[/size][/font][font=Verdana][size=10pt]R3[/size][/font][font=宋体][size=10pt]所连接了一个[/size][/font][font=Verdana][size=10pt]LAN,[/size][/font][font=宋体][size=10pt]和[/size][/font][font=Verdana][size=10pt]LAN[/size][/font][font=宋体][size=10pt]中的[/size][/font][font=Verdana][size=10pt]DR[/size][/font][font=宋体][size=10pt]接口个地址[/size][/font][font=Verdana][size=9pt][/size][/font][/align]
[align=left][font=Verdana][size=9pt] [/size][/font][/align]
[align=left][font=Verdana][size=9pt]R1#show ip ospf data net adv 3.3.3.3 [/size][/font][/align]
[align=left][font=Verdana][size=9pt] OSPF Router with ID (1.1.1.1) (Process ID 10)[/size][/font][/align]
[align=left][font=Verdana][size=9pt] Net Link States (Area 0)[/size][/font][/align]
[align=left][font=Verdana][size=9pt] Routing Bit Set on this LSA
LS age: 972
Options: (No TOS-capability, DC)
LS Type: Network Links
Link State ID: 10.1.1.3 (address of Designated Router)
Advertising Router: 3.3.3.3
LS Seq Number: 80000006
Checksum: 0x3D6
Length: 40
[/size][/font][font=Verdana][size=9pt] Network Mask: /24[/size][/font][font=Verdana][size=9pt]
Attached Router: 3.3.3.3
Attached Router: 2.2.2.2
Attached Router: 4.4.4.4
Attached Router: 5.5.5.5[/size][/font][/align]
[align=left][font=Verdana][size=9pt] [/size][/font][/align]
[align=left][font=Verdana][size=10pt]LSA2[/size][/font][font=宋体][size=10pt]里明确的交代了[/size][/font][font=Verdana][size=10pt]LAN[/size][/font][font=宋体][size=10pt]中的网络掩码[/size][/font][font=Verdana][size=10pt].[/size][/font][font=Verdana][size=9pt][/size][/font][/align]
[align=left][font=Verdana][size=10pt]---------------------------------------------------------[/size][/font][font=Verdana][size=9pt][/size][/font][/align]
[align=left][font=宋体][size=10pt]接下来看一看[/size][/font][font=Verdana][size=10pt]R1[/size][/font][font=宋体][size=10pt]上面计算到达这个[/size][/font][font=Verdana][size=10pt]LAN[/size][/font][font=宋体][size=10pt]的[/size][/font][font=Verdana][size=10pt]SPF[/size][/font][font=宋体][size=10pt]输出信息[/size][/font][font=Verdana][size=9pt][/size][/font][/align]
[align=left][font=Verdana][size=9pt] [/size][/font][/align]
[align=left][font=Verdana][size=10pt]R1#debug ip ospf spf [/size][/font][font=Verdana][size=9pt][/size][/font][/align]
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[align=left][font=Verdana][size=10pt]OSPF: Add Network Route to 10.1.1.0 Mask /24. Metric: 74, Next Hop: 13.1.1.3
*Jul 9 18:38:39.255: OSPF: insert route list LS ID 10.1.1.3, type 2, adv rtr 3.3.3.3
*Jul 9 18:38:39.255: It is a network LSA 10.1.1.3. Router Count 4
*Jul 9 18:38:39.255: Processing router id 3.3.3.3
*Jul 9 18:38:39.255: New newdist 74 olddist 64
*Jul 9 18:38:39.255: Processing router id 2.2.2.2
*Jul 9 18:38:39.255: Add better path to LSA ID 2.2.2.2, gateway 10.1.1.2, dist 74
*Jul 9 18:38:39.255: Add path: next-hop 13.1.1.3, interface Serial2/0
*Jul 9 18:38:39.255: Processing router id 4.4.4.4
*Jul 9 18:38:39.255: Add better path to LSA ID 4.4.4.4, gateway 10.1.1.4, dist 74
*Jul 9 18:38:39.255: Add path: next-hop 13.1.1.3, interface Serial2/0
*Jul 9 18:38:39.255: Processing router id 5.5.5.5
*Jul 9 18:38:39.255: Add better path to LSA ID 5.5.5.5, gateway 10.1.1.5, dist 74
*Jul 9 18:38:39.255: Add path: next-hop 13.1.1.3, interface Serial2/0
*Jul 9 18:38:39.255: It is a router LSA 5.5.5.5. Link Count 1
[/size][/font][font=Verdana][size=10pt]*Jul 9 18:38:39.255: Processing link 0, id 10.1.1.3, link data 10.1.1.5, type 2[/size][/font][font=Verdana][size=10pt]
*Jul 9 18:38:39.255: Ignore newdist 84 olddist 74
*Jul 9 18:38:39.255: It is a router LSA 4.4.4.4. Link Count 1
[/size][/font][font=Verdana][size=10pt]*Jul 9 18:38:39.255: Processing link 0, id 10.1.1.3, link data 10.1.1.4, type 2[/size][/font][font=Verdana][size=10pt]
*Jul 9 18:38:39.255: Ignore newdist 84 olddist 74
*Jul 9 18:38:39.255: It is a router LSA 2.2.2.2. Link Count 1
[/size][/font][font=Verdana][size=10pt]*Jul 9 18:38:39.255: Processing link 0, id 10.1.1.3, link data 10.1.1.2, type 2[/size][/font][font=Verdana][size=10pt]
*Jul 9 18:38:39.255: Ignore newdist 84 olddist 74[/align]
[color=#0000ff]注意红色部分的link data 10.1.12,type 2 部分...这里我们可以联想一下LSA 1的输出信息.[/color]
[align=left][font=Verdana][size=10pt]R1#show ip ospf data router adv 3.3.3.3[/size][/font][font=Verdana][size=9pt][/size][/font][/align]
[align=left][font=Verdana][size=10pt] OSPF Router with ID (1.1.1.1) (Process ID 10)[/size][/font][font=Verdana][size=9pt][/size][/font][/align]
[align=left][font=Verdana][size=10pt] Router Link States (Area 0)[/size][/font][font=Verdana][size=9pt][/size][/font][/align]
[align=left][font=Verdana][size=10pt] LS age: 791
Options: (No TOS-capability, DC)
LS Type: Router Links
Link State ID: 3.3.3.3
Advertising Router: 3.3.3.3
LS Seq Number: 80000015
Checksum: 0x5BC0
Length: 60
Number of Links: 3[/size][/font][font=Verdana][size=9pt][/size][/font][/align]
[align=left][font=Verdana][size=10pt] Link connected to: another Router (point-to-point)
(Link ID) Neighboring Router ID: 1.1.1.1
(Link Data) Router Interface address: 13.1.1.3
Number of TOS metrics: 0
TOS 0 Metrics: 64[/size][/font][font=Verdana][size=9pt][/size][/font][/align]
[align=left][font=Verdana][size=10pt] Link connected to: a Stub Network
(Link ID) Network/subnet number: 13.1.1.0
(Link Data) Network Mask: 255.255.255.0
Number of TOS metrics: 0
TOS 0 Metrics: 64[/size][/font][font=Verdana][size=9pt][/size][/font][/align]
[align=left][font=Verdana][size=10pt] [color=#0000cc]Link connected to: [color=#ff0000]a Transit Network[/color]
(Link ID) Designated Router address: 10.1.1.3
[color=#ff0000] (Link Data) Router Interface address: 10.1.1.3
[/color] Number of TOS metrics: 0
TOS 0 Metrics: 10[/align]
[/color][size=3][color=#0000ff][size=2]前面输出的type 2在ospfv2中定义的是transit network. 而link Data在LSA1中的表示的是通告此LSA的ADV在LAN中的接口地址.也就是说在R1在SPF计算到达LAN的每一个接口时使用了LSA是类型1的.那么类型2的又有什么用呢?
大家是否发现LSA1包含的信息中并没有包含这个LAN的掩码.而LSA2却带上了掩码
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R1#show ip ospf data net adv 3.3.3.3 [/size][/font]
[align=left][font=Verdana][size=9pt] OSPF Router with ID (1.1.1.1) (Process ID 10)[/size][/font][/align]
[align=left][font=Verdana][size=9pt] Net Link States (Area 0)[/size][/font][/align]
[align=left][font=Verdana][size=9pt] Routing Bit Set on this LSA
LS age: 972
Options: (No TOS-capability, DC)
LS Type: Network Links
Link State ID: 10.1.1.3 (address of Designated Router)
Advertising Router: 3.3.3.3
LS Seq Number: 80000006
Checksum: 0x3D6
Length: 40
[/size][/font][font=Verdana][size=9pt] Network Mask: /24[/size][/font][font=Verdana][size=9pt]
Attached Router: 3.3.3.3
Attached Router: 2.2.2.2
Attached Router: 4.4.4.4
Attached Router: 5.5.5.5[/align]
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[align=left][size=3][color=#006666]结论[/color][/size][/align]
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[align=left][size=3][color=#0000ff]路由器在SPF运算时,使用LSA1确定如何到达此MAN..再使用LSA2确定到此MAN的掩码.这就是为什么LSA2要求被泛洪到整个区域的原因.也是LSA2最大的一个作用.[/color][/size][/align]
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[/size][/color][/size][/size][/font][/size][/font] 希望能看懂，学习ing ！！！
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