Shulou(Shulou.com)06/03 Report--

OSPF belongs to link-state routing protocol and is a public standard. In theory, there is no restriction on the size of the network. It supports the hierarchical design of the network, and the network can be divided into two layers, which is distinguished by the concept of "area".

-backbone area-non-backbone area

All non-backbone members must be directly connected to the backbone area in order to communicate normally.

Routers are also divided into different types because of the existence of areas:

-backbone router: a router in which all links belong to the backbone area

-non-backbone routers: routers in which all links belong to non-backbone areas

-area Border Router (*) [ABR:area border router]: must be connected to both backbone and non-backbone areas

-Autonomous system boundary router [ASBR:]: a router with the ability to introduce external routing, called OSPF's ASBR

How it works: using only hello messages, OSPF routing, only exchanging synchronization databases between OSPF neighbor routers: LSA-link state advertisement, link-state advertisements to calculate routing tables

Experimental topology diagram:

Lab step: routing and loopback configuration ip address

R1: 192.168.1.1/24 loopback1: 1.1.1.1/24

R2: 192.168.1.2/24 loopback1: 2.2.2.2/24

[r2] interface LoopBack 1

[r2-LoopBack1] ip add 2.2.2.2 255.255.255.0 configure ospf

[r2] ospf 1

[r2-ospf-1] area 0

[r2-ospf-1-area-0.0.0.0] net 192.168.1.2 0.0.0.0 (accurately declare the ip address of the interface of your directly connected network segment)

R1 has the same idea to configure.

After the ospf declaration is configured, neighbors will be established and many entries will pop up

The above 1murmur6 are the states in which the router establishes neighbors through ospf.

The following is the analysis of the crawling message: R1:

R2:

Analysis: Router ID is different. From figure 2, we can see that ospf packets are sent in the way of multicast (224.0.0.5). Through 4, we can see that the regional ID of ospf is consistent. Through 5, we can see that hello packets are sent once in 10 seconds, and the same through 7, we can see that the dead time is 40s, and the same through 6, we can see that options (special tag bits) is the same.

Verification: 1. Modify router ID the same as R1, restart ospf 1

After modifying the same router ID, the neighbor is disconnected, indicating that the router id of the router that directly establishes the neighbor relationship must not be the same. Modify the area ID to a number other than 0

So to establish the routing of neighbors, the area id must be the same 3. Modify hello time 20s

[r2] in gi 0/0/0

[r2-GigabitEthernet0/0/0] ospf timer hello 20

View [R2] dispaly ospf brief and view neighbor table [R2] dis ospf p bri

So the hello time must be the same, while the hello time changes, the dead time also changes, and is 4 times the change of hello. Modify the dead time to 100s, and the following prompt appears

Therefore, the dead time should also be consistent. To sum up, if the router that establishes the neighbor relationship directly, the router id must not be the same, so the routing for establishing the neighbor, the area id must be the same for the router that establishes the neighbor relationship, and the hello time must be the same. At the same time, the hello time changes, the dead time also changes, and the dead time of the router that establishes the neighbor relationship is 4 times the hello.

Through the analysis of the above points, we can provide some ideas when there are problems with network routing.

Welcome to subscribe "Shulou Technology Information " to get latest news, interesting things and hot topics in the IT industry, and controls the hottest and latest Internet news, technology news and IT industry trends.