** OSPF experiment I got an incomplete version of the title, only the first nine questions, and therefore did not finish, and later to the end there is no chance to make up on the back of the title, we will only look at the
Experiment 4 OSPF protocol analysis
1. View R2 's OSPF adjacency information, write and display the results of its command:
display ospf peer
2. The R1's router id changed to 3.3.3.3, write its command. Display OSPF brief information, see this change take effect. If you do not take effect, how to put it into effect?
Command is:
undo router id
router id 3.3.3.3
display ospf
Not in force, should be performed: the RESET ospf Process to take effect
3.6.1 OSPF protocol packet format
3. Analysis of intercepted messages, you can see the five OSPF protocol packets, please write the name of the five protocol packets. Hello and select a message, write the whole message structure (OSPF Hello header and message body).
Hello Packet packet, DB Description packets, LS Request message, LS Update message, LS Acknowledge message.
Hello packet structure as shown below:
4. The head of the OSPF protocol analysis , what role in OSPF Router ID is? How is it produced?
router ID effect are: ① as OSPF area uniquely identifies a router; ② the DR , the BDR election at the same time priority, router ID big elected as the DR .
router ID generation rule: ① the set if the command router ID , this is selected as the router ID . ② If no command Router ID , if loopback address, then select the maximum loopback address as the Router ID ; if no loopback address, then select a different interface addresses as the largest Router ID .
5. Analysis LSUpdate intercepted a message, write the message header, and write the message, there are several LSA? And the type of the corresponding LSA.
The following diagram, the packet header as OSPF Header content. Message contains . 3 Article the LSA , two stub type, a PTP type.
3.6.2 OSPF packet exchange process
6. Binding intercepted packets and DD packet field (MS, I, M), and the negotiation process to write the main DD consultations slave relationship.
After 2way, entered ExStart stage. R1 R2 sends a first empty DD packet, comprising its own router ID, which (MS, I, M) = (1,1,1), claimed to be Master; R2 DD received packets, comparing their R1 router ID and the router ID, found their router ID (2.2.2.2) (3.3.3.3) R1 is smaller than the router ID, so the R1 is set to Master, sending DD packets. ExStart end, determined based R1, R2 from the two routers have entered Exchange state.
7. Binding intercepted packets and DD packet field (MS, I, M, Seq), write a summary LSA information exchange process, and describes how to confirm implicitly that the reliable transport mechanism is active.
Slave returns step DD packet using the sequence number y transmitted new DD packets, wherein (MS, I, M, Seq) = (1,0,0, y), and carries the LSBD Master Slave in summary LSA; Master receives the message and sends the new packets DD, wherein (MS, I, M, Seq) = (1,0,0, y + 1), and carries the LSA in summary LSBD Master, because the experiment is only two stub router LSA type of structure, which is the most a DD packet sent by the Master, M indicates that this is the last DD packet. Master Slave receives the packet, and returns an acknowledgment packet, (MS, I, M, Seq) = (0,0,0, y + 1), LSA packet does not carry information, only that received Slave Master of the message.
Function and reliable transmission mechanism confirmed way: Master Slave By repeating the sequence number acknowledgment packets have been received Master, Master serial number by adding 1 to the acknowledgment has been received packets Slave.
8. A group of related binding intercepted LSR, LSU, and LSAck packets, reliable transport mechanism described in detail OSPF packets interaction is ensured.
R1 (router ID: 3.3.3.3, the master) to R2 (router ID: 2.2.2.2, from a) by the LSR packets, requesting the LSA, and in which the Link State Request field indicating the required summary of the LSA.
R2 After receiving the packet, returns LSU packets, which, like LSR LSA summary and R1 in.
After receiving the Slave LSU packets, LSA will return a message indicating that LSU has received the message.
Summary LSA message packet is consistent with LSU, and Sequence Number is also consistent with the LSU packets. So OSP F protocol to confirm reliable transport mechanism and the summaries using LSA Sequence Number in LSR, LSU, LSA packet interaction.
3.6.3 neighbor state machine
9. Please OSPF neighbor information on the state transition diagram, shown according R1 debug display.
OSPF 1: Neighbor 168.1.1.2 received state that is the beginning of OSPF neighbor state transition.
