OSPF網(wǎng)絡配置排錯

OSPF網(wǎng)絡配置排錯

網(wǎng)絡拓撲如圖10.1所示，配置完成后發(fā)現(xiàn)從R1到R4和R5所帶主機有時通有時不通，網(wǎng)絡通信出現(xiàn)故障。

圖10.1 BENET網(wǎng)絡拓撲圖

各路由器的配置如下所示：

R1配置

interface FastEthernet0/0

ip address 10.0.0.1 255.255.255.252

!

interface FastEthernet1/0

ip address 20.0.0.1 255.255.255.252

!

router ospf 1

network 10.0.0.0 0.0.0.3 area 0

network 20.0.0.0 0.0.0.3 area 0

R2配置

interface FastEthernet0/0

ip address 10.0.0.2 255.255.255.252

!

interface FastEthernet1/0

ip address 30.0.0.1 255.255.255.0

!

router ospf 1

network 10.0.0.0 0.0.0.3 area 0

network 30.0.0.0 0.0.0.255 area 1

R3配置

interface FastEthernet0/0

ip address 30.0.0.5 255.255.255.0

!

interface FastEthernet1/0

ip address 20.0.0.2 255.255.255.252

!

router ospf 1

network 20.0.0.0 0.0.0.3 area 0

network 30.0.0.0 0.0.0.255 area 2

R4配置

interface FastEthernet0/0

ip address 30.0.0.2 255.255.255.0

!

router ospf 1

network 30.0.0.0 0.0.0.255 area 1

R5配置

interface FastEthernet0/0

ip address 30.0.0.6 255.255.255.0

!

router ospf 1

network 30.0.0.0 0.0.0.255 area 2

在處理OSPF故障時，一般首先查看路由表，通過路由表發(fā)現(xiàn)路由異常；然后根據(jù)出現(xiàn)異常的路由條目的目的地址，檢查所屬路由器的配置、鄰接關系等排除故障。

由于R1到R4、R5出現(xiàn)通信問題，所以查看R1的路由表，如下所示：

20.0.0.0/30 is subnetted, 1 subnets

C 20.0.0.0 is directly connected, FastEthernet1/0

10.0.0.0/30 is subnetted, 1 subnets

C 10.0.0.0 is directly connected, FastEthernet0/0

30.0.0.0/24 is subnetted, 1 subnets

O IA 30.0.0.0 [110/2] via 20.0.0.2, 00:32:40, FastEthernet1/0

[110/2] via 10.0.0.2, 00:32:40, FastEthernet0/0

發(fā)現(xiàn)路由表中出現(xiàn)了負載均衡的路由條目，但是在網(wǎng)絡規(guī)劃中沒有負載均衡的要求。

由于30.0.0.0/24網(wǎng)段出現(xiàn)故障，所以檢查配置此網(wǎng)段的路由器。經(jīng)檢查檢查配置發(fā)現(xiàn)接口地址的子網(wǎng)掩碼配置有誤，將/30的掩碼誤配置成/24的掩碼導致的網(wǎng)絡通信故障。

網(wǎng)絡管理員更改配置如下所示：

R2配置：

interface FastEthernet1/0

ip address 30.0.0.1 255.255.255.252

R3配置：

interface FastEthernet0/0

ip address 30.0.0.5 255.255.255.252

R4配置：

interface FastEthernet0/0

ip address 30.0.0.2 255.255.255.252

R5配置：

interface FastEthernet0/0

ip address 30.0.0.6 255.255.255.252

更改配置完成后，再次查看路由表已經(jīng)恢復正常，網(wǎng)絡通信也已正常。

當運行OSPF協(xié)議的網(wǎng)絡出現(xiàn)故障時，查看LSDB也可以快速有效的判斷問題，上述故障案例中也可以通過LSDB發(fā)現(xiàn)故障。

當OSPF網(wǎng)絡出現(xiàn)故障時，可以使用show ip ospf database命令R1查看LSDB，如下：

OSPF Router with ID (10.0.0.1) (Process ID 1)

Router Link States (Area 0)

Link ID ADV Router Age Seq# Checksum Link count

10.0.0.1 10.0.0.1 953 0x80000005 0x00CAFC 2

30.0.0.1 30.0.0.1 605 0x8000000A 0x0011C2 1

30.0.0.5 30.0.0.5 943 0x80000006 0x009723 1

Net Link States (Area 0)

Link ID ADV Router Age Seq# Checksum

10.0.0.1 10.0.0.1 1448 0x80000002 0x0048B3

20.0.0.2 30.0.0.5 943 0x80000002 0x00C60E

Summary Net Link States (Area 0)

Link ID ADV Router Age Seq# Checksum

30.0.0.0 30.0.0.1 97 0x80000004 0x00F00B

30.0.0.0 30.0.0.5 943 0x80000002 0x00DC1D

R1的LSDB中粗體部分出現(xiàn)不同的路由器發(fā)送了相同的LSA，這時可以使用show ip ospf database summary命令進一步查看R1路由器收到的類型3的LSA信息如下：

OSPF Router with ID (10.0.0.1) (Process ID 1)

Summary Net Link States (Area 0)

Routing Bit Set on this LSA

LS age: 163

Options: (No TOS-capability, DC, Upward)

LS Type: Summary Links(Network)

Link State ID: 30.0.0.0 (summary Network Number)

Advertising Router: 30.0.0.1

LS Seq Number: 80000004

Checksum: 0xF00B

Length: 28

Network Mask: /24

TOS: 0 Metric: 1

Routing Bit Set on this LSA

LS age: 1009

Options: (No TOS-capability, DC, Upward)

LS Type: Summary Links(Network)

Link State ID: 30.0.0.0 (summary Network Number)

Advertising Router: 30.0.0.5

LS Seq Number: 80000002

Checksum: 0xDC1D

Length: 28

Network Mask: /24

TOS: 0 Metric: 1

兩臺路由器發(fā)布的Summary NET的LSA完全相同，這就造成了路由的負載均衡，查看路由表有網(wǎng)段30.0.0.0/24網(wǎng)段的負載均衡。然而實際網(wǎng)絡并不是負載均衡的網(wǎng)絡，檢查配置發(fā)現(xiàn)子網(wǎng)掩碼配置錯誤導致路由選路問題。