Discussion on OSPF starting from 4 layer 3 switches

Hello:

1. First of all, your topology uses ACCESS to achieve interconnection, and the PC is also connected to ACCESS (note: you can use trunk to connect to the PC). Did you use it? vlan10 20 30 40, it is equivalent to using your four switches as routers, then there must be corresponding SVI ports on each of your switches;

2. If the first one is true, then you are establishing When using OSPF on the entire network, your PC section can be fully directly connected or declared. It doesn't matter. This is an OSPF area (area 0). Then the establishment will be successful only when the LSDBs on your four switches are the same. If You said you have route loss, then check your OSPF database to see which one is missing (in this case, OSPF is not established successfully) show ip ospf da;

3, second item Established, your PC1 PING PC2 is definitely connected, and it is PC2---SW3---SW1---PC1. OSPF routing is based on cost;

4. OSPF, COST value option , is used for route selection, and can only affect the router you set or change. It is invalid for adjacent routers. It can only affect your outgoing traffic, but not your incoming traffic;

The above is very clear: pay attention to whether the vlan corresponding to the PC on your SW3 SW1 has an SVI port. Without SVI, it cannot be sent in;

Check whether your vlan is successfully established; whether the interface is open; etc.< /p>