为什么第三层交换机丢弃ping包？

Question

我正在尝试从PC2 (而不是PC1，图片中有错误)到路由器的intG0/0，但是包被丢弃在沿着路径的L3交换机上。我尝试过设置一个默认的静态路由，一个默认的网关，一个即插即用的路由器技术，甚至是来自L3交换机和路由器的ospf网络广告。

SWITCH0 0：

Switch#show running-config 
Building configuration...

Current configuration : 1203 bytes
!
version 12.2
no service timestamps log datetime msec
no service timestamps debug datetime msec
no service password-encryption
!
hostname Switch
!
!
!
!
!
spanning-tree mode pvst
spanning-tree extend system-id
!
interface FastEthernet0/1
 switchport access vlan 10
 switchport mode access
!
interface FastEthernet0/2
 switchport access vlan 20
 switchport mode access
!
interface FastEthernet0/3
 switchport mode trunk
!
interface FastEthernet0/4
!
interface FastEthernet0/5
!
interface FastEthernet0/6
!
interface FastEthernet0/7
!
interface FastEthernet0/8
!
interface FastEthernet0/9
!
interface FastEthernet0/10
!
interface FastEthernet0/11
!
interface FastEthernet0/12
!
interface FastEthernet0/13
!
interface FastEthernet0/14
!
interface FastEthernet0/15
!
interface FastEthernet0/16
!
interface FastEthernet0/17
!
interface FastEthernet0/18
!
interface FastEthernet0/19
!
interface FastEthernet0/20
!
interface FastEthernet0/21
!
interface FastEthernet0/22
!
interface FastEthernet0/23
!
interface FastEthernet0/24
!
interface GigabitEthernet0/1
!
interface GigabitEthernet0/2
!
interface Vlan1
 no ip address
 shutdown
!
!
!
!
line con 0
!
line vty 0 4
 login
line vty 5 15
 login
!
!
!
!
end

SWITCH1 1：

Switch#show running-config 
Building configuration...

Current configuration : 1124 bytes
!
version 12.2
no service timestamps log datetime msec
no service timestamps debug datetime msec
no service password-encryption
!
hostname Switch
!
!
!
!
!
spanning-tree mode pvst
spanning-tree extend system-id
!
interface FastEthernet0/1
 switchport mode trunk
!
interface FastEthernet0/2
 switchport mode trunk
!
interface FastEthernet0/3
!
interface FastEthernet0/4
!
interface FastEthernet0/5
!
interface FastEthernet0/6
!
interface FastEthernet0/7
!
interface FastEthernet0/8
!
interface FastEthernet0/9
!
interface FastEthernet0/10
!
interface FastEthernet0/11
!
interface FastEthernet0/12
!
interface FastEthernet0/13
!
interface FastEthernet0/14
!
interface FastEthernet0/15
!
interface FastEthernet0/16
!
interface FastEthernet0/17
!
interface FastEthernet0/18
!
interface FastEthernet0/19
!
interface FastEthernet0/20
!
interface FastEthernet0/21
!
interface FastEthernet0/22
!
interface FastEthernet0/23
!
interface FastEthernet0/24
!
interface GigabitEthernet0/1
!
interface GigabitEthernet0/2
!
interface Vlan1
 no ip address
 shutdown
!
!
!
!
line con 0
!
line vty 0 4
 login
line vty 5 15
 login
!
!
!
!
end

MULTILAYER SWITCH0 0：

Switch#show running-config 
Building configuration...

Current configuration : 1643 bytes
!
version 12.2(37)SE1
no service timestamps log datetime msec
no service timestamps debug datetime msec
no service password-encryption
!
hostname Switch
!
!
!
!
!
!
ip routing
!
!
!
!
!
!
!
!
!
!
!
!
!
!
spanning-tree mode pvst
!
!
!
!
!
!
interface FastEthernet0/1
 switchport trunk encapsulation dot1q
 switchport mode trunk
!
interface FastEthernet0/2
!
interface FastEthernet0/3
!
interface FastEthernet0/4
!
interface FastEthernet0/5
!
interface FastEthernet0/6
!
interface FastEthernet0/7
!
interface FastEthernet0/8
!
interface FastEthernet0/9
!
interface FastEthernet0/10
!
interface FastEthernet0/11
!
interface FastEthernet0/12
!
interface FastEthernet0/13
!
interface FastEthernet0/14
!
interface FastEthernet0/15
!
interface FastEthernet0/16
!
interface FastEthernet0/17
!
interface FastEthernet0/18
!
interface FastEthernet0/19
!
interface FastEthernet0/20
!
interface FastEthernet0/21
!
interface FastEthernet0/22
!
interface FastEthernet0/23
!
interface FastEthernet0/24
!
interface GigabitEthernet0/1
!
interface GigabitEthernet0/2
!
interface Vlan1
 no ip address
 shutdown
!
interface Vlan10
 mac-address 0002.16d2.a901
 ip address 192.168.1.2 255.255.255.0
!
interface Vlan20
 mac-address 0002.16d2.a902
 ip address 192.168.2.2 255.255.255.0
!
interface Vlan30
 description admin
 mac-address 0002.16d2.a903
 no ip address
!
router ospf 1
 log-adjacency-changes
 network 192.168.1.0 0.0.0.255 area 0
 network 192.168.2.0 0.0.0.255 area 0
!
ip default-gateway 192.168.0.1
ip classless
ip route 0.0.0.0 0.0.0.0 192.168.0.1 
!
ip flow-export version 9
!
!
!
!
!
!
!
!
line con 0
!
line aux 0
!
line vty 0 4
 login
!
!
!
!
end

ROUTER0 0：

Router#show running-config
Building configuration...

Current configuration : 846 bytes
!
version 15.1
no service timestamps log datetime msec
no service timestamps debug datetime msec
no service password-encryption
!
hostname Router
!
!
!
!
!
!
!
!
ip cef
no ipv6 cef
!
!
!
!
license udi pid CISCO1941/K9 sn FTX1524IP37-
!
!
!
!
!
!
!
!
!
!
!
spanning-tree mode pvst
!
!
!
!
!
!
interface GigabitEthernet0/0
 ip address 192.168.0.1 255.255.255.0
 duplex auto
 speed auto
!
interface GigabitEthernet0/0.10
 encapsulation dot1Q 10
 no ip address
!
interface GigabitEthernet0/0.20
 encapsulation dot1Q 20
 no ip address
!
interface GigabitEthernet0/1
 no ip address
 duplex auto
 speed auto
 shutdown
!
interface Vlan1
 no ip address
 shutdown
!
router ospf 1
 log-adjacency-changes
 network 192.169.0.0 0.0.0.255 area 0
!
ip classless
!
ip flow-export version 9
!
!
!
!
!
!
!
!
line con 0
!
line aux 0
!
line vty 0 4
 login
!
!
!
end

Answer 1

你有一些问题。例如，路由器了解其他网络的唯一方法是通过OSPF，但是您没有参与OSPF的接口，因为OSPF网络语句与任何接口不匹配。

另外，如果第三层交换机正在路由，正如您所配置的那样，那么您不应该使用default-gateway命令。这是为第二层交换，而不是第三层开关.

您在第3层交换机上配置的默认路由实际上应该在路由器上，路由器上的OSPF应该有default-information originate命令。

路由器不应该配置VLAN的子接口，因为VLAN之间的路由应该发生在第3层交换机上。

第三层交换机应具有与路由器集的接口和路由器与交换机(通常为/30或/31网络)之间的链路的IP地址，以便该网络只有两个地址。

您确实应该在接口上使用description命令来判断接口在另一端连接到什么。我只是猜测中继接口是交换机之间的连接，因此这意味着第三层交换机上的路由器连接在VLAN 1中，而VLAN 1在第三层交换机中没有寻址。

另外，您需要确保使用全局vlan 命令在交换机上实际配置VLAN。这与创建SVI不同。

我不知道您在哪里配置了DHCP来为PC分配寻址和网关。