P2P与P2MP的一字之差，为何让Ping彻底“迷路”？

不做菜鸟的网工
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前言

在OSPF多路访问网络中，接口网络类型P2P与P2MP看似相似，却暗藏玄机。本文通过实验发现：当R2为P2P、R3为P2MP时，R3产生的Router LSA多出一条32位主机路由（10.0.0.3/32），而R2只通告所在网段。这导致R2默认ping R3的回环口失败，必须指定源IP才能通。文章深入剖析LSA差异与路由计算逻辑，揭示网络类型不一致引发的“ping不通”陷阱，并给出解决建议。

网络拓扑

Pasted image 20260512112826.png

LSA同步 [P2P & P2MP的区别]

区别：P2P网络接口不会产生32位主机路由，P2MP网络接口会产生32位主机路由

R1 向 R2/R3同步 1类LSA路由 Stubnet+P2P Pasted image 20260512113554.png

CLI命令查验

[R1]dis ospf lsdb router 

         OSPF Process 1 with Router ID 1.1.1.1
                         Area: 0.0.0.0
                 Link State Database
	
	......此处省略其他LSA

    Type      : Router
    LS ID     : 1.1.1.1
    Adv Rtr   : 1.1.1.1
    LS age    : 836
    Len       : 72
    Options   : O E 
    Seq#      : 80000005
    Checksum  : 0x623d
    Link Count: 4
       Link ID: 2.2.2.2
       Data   : 10.0.0.1
       Link Type: P-2-P       
       Metric : 1
       Link ID: 3.3.3.3
       Data   : 10.0.0.1
       Link Type: P-2-P       
       Metric : 1
       Link ID: 1.1.1.1
       Data   : 255.255.255.255
       Link Type: StubNet     
       Metric : 0
       Link ID: 10.0.0.1
       Data   : 255.255.255.255
       Link Type: StubNet     
       Metric : 0

	......此处省略其他LSA

[R1]

此时将R2的G0/0 OSPF网络接口类型修改为P2P。配置命令如下：

#
interface GigabitEthernet0/0
 port link-mode route
 combo enable copper
 ip address 10.0.0.2 255.255.255.0
 ospf timer hello 30
 ospf timer dead 120
 ospf network-type p2p
 ospf 1 area 0.0.0.0

image.png

然后此时查看R2产生的LSA

[R2]dis ospf lsdb router 

         OSPF Process 1 with Router ID 2.2.2.2
                         Area: 0.0.0.0
                 Link State Database
	
	......此处省略其他LSA

    Type      : Router
    LS ID     : 2.2.2.2
    Adv Rtr   : 2.2.2.2
    LS age    : 1179
    Len       : 60
    Options   : O E 
    Seq#      : 80000004
    Checksum  : 0x12ab
    Link Count: 3
       Link ID: 1.1.1.1
       Data   : 10.0.0.2  【P2P直连的地址】
       Link Type: P-2-P       
       Metric : 1
       Link ID: 2.2.2.2
       Data   : 255.255.255.255
       Link Type: StubNet     
       Metric : 0
       Link ID: 10.0.0.0  【连接的网段地址】
       Data   : 255.255.255.0
       Link Type: StubNet     
       Metric : 1
[R2]


# 对比 R3 P2MP R3会产生32位主机路由
[R2]dis ospf lsdb router 

         OSPF Process 1 with Router ID 2.2.2.2
                         Area: 0.0.0.0
                 Link State Database


    Type      : Router
    LS ID     : 3.3.3.3
    Adv Rtr   : 3.3.3.3
    LS age    : 1181
    Len       : 60
    Options   : O E 
    Seq#      : 80000004
    Checksum  : 0x624c
    Link Count: 3
       Link ID: 1.1.1.1
       Data   : 10.0.0.3
       Link Type: P-2-P       
       Metric : 1
       Link ID: 3.3.3.3
       Data   : 255.255.255.255
       Link Type: StubNet     
       Metric : 0
       Link ID: 10.0.0.3    【32位主机路由】【P2MP与P2P的区别】
       Data   : 255.255.255.255
       Link Type: StubNet     
       Metric : 0
	
	......

Pasted image 20260512115359.png

造成的问题？

R2 和 R3分别查询OSPF路由表就会发现 R3不存在10.0.0.2/32的主机路由

[R2]dis ospf routing 

         OSPF Process 1 with Router ID 2.2.2.2
                  Routing Table

 Routing for network
 Destination        Cost     Type    NextHop         AdvRouter       Area
 3.3.3.3/32         2        Stub    10.0.0.1        3.3.3.3         0.0.0.0
 10.0.0.0/24        1        Stub    0.0.0.0         2.2.2.2         0.0.0.0
 1.1.1.1/32         1        Stub    10.0.0.1        1.1.1.1         0.0.0.0
 10.0.0.1/32        1        Stub    10.0.0.1        1.1.1.1         0.0.0.0
 10.0.0.3/32        2        Stub    10.0.0.1        3.3.3.3         0.0.0.0
 2.2.2.2/32         0        Stub    0.0.0.0         2.2.2.2         0.0.0.0

 Total nets: 6  
 Intra area: 6  Inter area: 0  ASE: 0  NSSA: 0 
[R2]

[R3]dis ospf routing 

         OSPF Process 1 with Router ID 3.3.3.3
                  Routing Table

 Routing for network
 Destination        Cost     Type    NextHop         AdvRouter       Area
 3.3.3.3/32         0        Stub    0.0.0.0         3.3.3.3         0.0.0.0
 10.0.0.0/24        3        Stub    10.0.0.1        2.2.2.2         0.0.0.0
 1.1.1.1/32         1        Stub    10.0.0.1        1.1.1.1         0.0.0.0
 10.0.0.1/32        1        Stub    10.0.0.1        1.1.1.1         0.0.0.0
 10.0.0.3/32        0        Stub    0.0.0.0         3.3.3.3         0.0.0.0
 2.2.2.2/32         2        Stub    10.0.0.1        2.2.2.2         0.0.0.0

 Total nets: 6  
 Intra area: 6  Inter area: 0  ASE: 0  NSSA: 0 
[R3]

造成的问题就是R2-R3 Ping测试 不指定回环口导致Ping不通

[R2]ping 3.3.3.3
Ping 3.3.3.3 (3.3.3.3): 56 data bytes, press CTRL+C to break
Request time out
Request time out
Request time out
Request time out
Request time out

--- Ping statistics for 3.3.3.3 ---
5 packet(s) transmitted, 0 packet(s) received, 100.0% packet loss
[R2]%May 12 12:01:17:238 2026 R2 PING/6/PING_STATISTICS: Ping statistics for 3.3.3.3: 5 packet(s) transmitted, 0 packet(s) received, 100.0% packet loss.

[R2]
[R2]ping -a 2.2.2.2 3.3.3.3
Ping 3.3.3.3 (3.3.3.3) from 2.2.2.2: 56 data bytes, press CTRL+C to break
56 bytes from 3.3.3.3: icmp_seq=0 ttl=254 time=1.462 ms
56 bytes from 3.3.3.3: icmp_seq=1 ttl=254 time=1.260 ms
56 bytes from 3.3.3.3: icmp_seq=2 ttl=254 time=1.436 ms
56 bytes from 3.3.3.3: icmp_seq=3 ttl=254 time=1.383 ms
56 bytes from 3.3.3.3: icmp_seq=4 ttl=254 time=1.253 ms

--- Ping statistics for 3.3.3.3 ---
5 packet(s) transmitted, 5 packet(s) received, 0.0% packet loss
round-trip min/avg/max/std-dev = 1.253/1.359/1.462/0.087 ms
[R2]%May 12 12:01:37:753 2026 R2 PING/6/PING_STATISTICS: Ping statistics for 3.3.3.3: 5 packet(s) transmitted, 5 packet(s) received, 0.0% packet loss, round-trip min/avg/max/std-dev = 1.253/1.359/1.462/0.087 ms.

[R2]
[R2]
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