Learn about the CCIE Routing Protocol

Self-taught CCIE route protocol troubleshooting 01. What protocol does RIP transmit information and what mechanism is used to calculate the optimal route? RIP updates route information based on UDP port 520 using the BELLMEN-FORD algorithm. The basic principle is to follow the minimum hop count principle. Therefore, the route table path is not necessarily the optimal path. 02. In a non-broadcast environment, what commands can be used to send and receive route information based on unicast? R12001 uses the broadcast address 255.255.255.255.255 to send information on the INTERFACE. In non-broadcast environments, it mainly sets the PASS-INTERFACE on the INTERFACE or rejects the broadcast address through the access list. Generally, only the neighbor can be manually specified. In the routing mode, the neighbor ip-address is used. 03. Why is the maximum number of hops supported by RIP Based on 15 hops and 16 hops inaccessible? In the RIP message format, the measured value is 32 bits, that is, the maximum RIP value can be 2 to the power of 32 hops, and the RIP update period is 30 s, if there is such a large network, how slow its convergence is, that is, the reason why RIP is only suitable for small networks. 04. Why does RIP not support discontinuous subnets? How does it work? The example shows that RIP has a class protocol and does not support non-consecutive subnets. By default, it will automatically summarize at the main network boundary. The following example describes the rules for receiving and sending RIP messages. 192. 168.1.1/24---r1-------10.10.1/30---------------R2---192.168.1.3/24 configure the RIP Protocol sending rule between R1 and R2: If the sent Route IP address and the sending interface are in the same master network and have the same subnet mask, if the subnet mask is not the same, it is discarded. If the IP address of the route to be sent is not in the same master network as the sending interface, the route is automatically summarized at the boundary and then forwarded. Receiving rule: if the received Route IP address cannot be obtained from other interfaces, add it to the routing table. If the received Route IP address information is obtained from other interfaces, deny the route information. According to the sending and receiving rules, we can get that 192.168.1.1/24 is summarized into 192.168.1.0/24 at R1, and in R2, there is an interface 192.168.1.3/24, therefore, the summary information sent from R1 is discarded. Therefore, RIP does not support discontinuous subnets. 05. Why does RIP not support VLSM? How does it work? The example shows that this principle is the same as that of the unsupported discontinuous subnet. As shown in the figure above, replace the IP address on the left with 10.10.9.1/24, which is only one side, and set a loopback interface to 10.10.10.5/30. According to the sending principle, if the IP address of the sent route is in the same master network as the IP address of the sent interface, and the subnet mask is the same, normal forwarding can be performed. If the mask is different, no forwarding is performed, you can go to "show ip route" on R2. no route information is available, but 10.10.10.5/30 is available. 06. What mechanism does RIP use to prevent routing loops? When a routing loop occurs, which two features can reduce the impact of the loop? RIP uses horizontal segmentation and toxic horizontal segmentation to prevent routing loops. The principle of horizontal segmentation is that route information is received from this interface and will not be sent from this interface. The horizontal division of toxicity is that the route information received from this interface sets the number of hops to the maximum (inaccessible) and then sends the packets from this interface, when other routers are routed to this route, they are discarded. (In my opinion, this is unnecessary, so it is best to set horizontal segmentation ). When a routing loop occurs, there are two mechanisms in RIP: one is to count to the maximum, and the other is to keep the timer. Generally, the count is set to 16. When a routing loop occurs, the number of hops continuously increases between two or more routers. When the number of hops increases to 16, if the target is not reachable, the sending is terminated. The principle of holding the timer is to delete the route entries from the routing table when the sent route does not receive the re-confirmation and the timer overflows. 07. What features does r12002 provide compared with r12001? The following features are added to the IP packet in r12002: Subnet Mask, multicast, authentication, Next Hop address, and route tag. 08. What is the role of the route tag in r12002? Routing labels prevent routing loops. For example, if ten static routes are redistributed to the RIP domain and marked as 20, the 10 static routes are sent to the OSPF domain, when the OSPF domain sends these 10 static routes to RIP again, the RIP sending mark is bound by itself, so the route information is rejected. Topology: Three routers are connected. 09. Does r12002 support authentication? What kind of authentication is supported? R12002 supports Simple plaintext authentication 10. Can r00002 solve non-continuous network problems by default? No. By default, r00002 disables automatic summary. You must use the command: no auto-summary in routing mode. Can IGRP/OSPF 01. Kerberos be compatible with other routing protocols? Can it be shared with other protocols? Compatible. It is a CISCO proprietary protocol, so it cannot be configured on non-CISCO devices. It can be shared with other protocols through redistribution. 02. What is the Management Distance of the VPN gateway and the total Management Distance of the VPN gateway? The Internal Management Distance of the network is 90, the external value is 170, and the summary is 5 03. What is the biggest difference between IGRP and RIP? For example, the biggest difference between two types of routes and RIP is that IGRP supports non-load balancing, but RIP does not. IGRP has three types of routes: internal routes, system routes, and external routes. 04. What types of tables are maintained by the VPN protocol? What is the role of the AS number in the IMG? Maintain the neighboring table, route table, and Topology table. The AS number here can be a set of routers under the same management in a self-Smelting System domain. 05. What are the IP protocol numbers of igrp vpn, and what are the biggest disadvantages of the update cycle compared with RIP? They are 9 and 88 respectively, and the update period is 90 seconds. The biggest drawback is that the network convergence speed is slow when the network topology changes. 06. The calculation of EIGPR metric values is mainly based on the two lazy measurement values. If you want to change the measurement value, which one will change in general? Why? Bandwidth and latency are generally modified because it is only used for IGRP and OSPF, and the bandwidth is also used for the calculation of the OSPF path cost. Therefore, modifying the bandwidth may affect the OSPF protocol. 07. Why does it mean that VPN is neither a distance vector protocol nor a link status protocol? VPN is an advanced distance vector protocol. It sends and updates route information based on the neighbor router. However, it also saves a route topology table. When the network topology changes, it only sends the changed route information. When the route table changes, the entire route table is updated. 08. Is there a loop in the routing of the OSPF protocol itself? Why? No loop exists in the network. Because it uses the DUAL algorithm, when selecting the optimal path, it is a non-circular path. 09. Is there a difference between the measurement calculation of the ospf and IGRP? What is the difference? The difference is that the value of the OSPF metric value must be multiplied by 256 10 Based on the IGRP value. by sending and confirming HELL0 data packets, VPN establishes a neighbor relationship. What is the update cycle of HELL0 data packets on a WAN or a link with a speed greater than T1? What is the update cycle for low links (less than T1? On a wide area network or a link with a speed greater than T1, the update cycle of HELLO packets is 5 seconds, while that of the T1 link is 60 seconds. 11. What conditions should I meet before I establish a neighbor in the kernel network? The IP address of the link should be in the same subnet, And the subnet mask should be the same. The constant K value at both ends should be the same. The receiver router should be in the same autonomous system as the sender router. 12. What is the meaning of "SRTT, RTO, and Q" in the output of "show ip VPN nei" in the image "in the kernel of the kernel? SRTT (smooth round-trip time): the average value of the time when a data packet is sent and the time when a data packet is received. RTO: The time for sending a data packet and waiting for response. Q: The number of data packets sent to the remote router. 13. What is FD, RD, and FC? FD: feasible distance. The measurement value calculated from the current vro to the remote vro. RD: The reported distance (also called the advertised distance). The measurement value from the neighboring vro to the remote vro. FC: feasible condition, the measurement value of the distance advertised by the neighbor should be smaller than the feasible distance calculated by the neighbor and used to select a feasible route to accelerate route convergence. 14. What is a passive route and what is an active route? Why does it generate an active route? Active route: The route table changes due to the loss of Route entries or a change in the network topology. If no feasible route entry is available, the route table enters the active query status, find the lost route information, which is called active route query. Passive route: In the route table, the remote route information entries that can be reached through the next hop. 15. What is the state mechanism of the DUAL algorithm? VPN uses the Diffusion Algorithm (DUAL) to calculate the optimal route information of a non-ring network. Unlike the traditional distance vector protocol, it saves a topology table to speed up convergence. 16. What is the query of the kernel, and what is the function of the query? In the query of a route entry in the route table, the query is performed when the route entry is disconnected but no route entry is feasible. 17. Which types of data packets are contained in the network, which are reliable and which are unreliable? Five types of data packets are used in the Network: 1. Hell0 2. Confirm 3. Update 4. query 5. The first two types of data are unreliable, and the last three types are reliable. 18. What is a stuck activity status? In general, what kind of command is used to find the error point? When in a large network environment, the SIA status may occur, that is, the router is always in the query status (also called active status) of the VPN gateway ), when a route query message is sent and no response is received, it is in this status. Generally, this status lasts for three minutes, but for a large network environment, when a neighbor router receives this packet to find the lost route information, it finds that it is not in progress and sends the query information to other neighbors. This keeps sending, and there may be network boundaries, are there any lost route information entries found. But there are several reasons for this SIA: 1. It may be that the remote link is DOWN. 2. Problems at the first or second layer. In general, run the command to view the show ip VPN topo active 19 on each adjacent router. What will happen if the K value does not match in OSPF? The OSPF neighbor cannot be created normally. 20. When configuring the Server Load balancer and non-Server Load balancer, which of the following commands can be enabled after the variables are configured for the configuration of the Network Load balancer and the non-Server Load balancer that is proportional to the link measurement value? Traffic-share min Traffic-share l [1] OSPF 01. How does OSPF prevent routing loops? 1. OSPF in the region adopts the SPF algorithm, and the algorithm itself has no loops. 2. each region is adjacent to the Region 0 to ensure that there is no ring between the regions. when connected to different AS, the source route may be lost 02. what are the network types of OSPF? Point-to-point, point-to-point, broadcast, NBMA, and virtual link 03. What are the statuses of OSPF neighbor routers? In which status do I select the master-slave relationship? DOWN, ATTEMPT, INIT, 2-WAY, EXSTART, EXCHANGE, LOADING, and FULL select the master-slave relationship in the EXSTART status 04. What are the group types of OSPF? Which type starts to determine the master-slave relationship? HELLO data packet database description (DBD) Link Status request link status update link status confirmation 05. Which network type is used for the attempt status of the ospf neighbor router? Which router types are used for NBMA 06. OSPF? In the backbone router area, the router ABRASBR 07. What types of OSPF areas are available? Backbone area general area peripheral area full peripheral area non-full peripheral area 08. What are common LSA types of OSPF? What are the specific functions of each LSA? Router LSA: LSA generated by the router itself, including its own links and interface status information network LSA: generated by the DR, including the summary of all link status information networks in the region LSA: this is generated by the API and the routing information in a region is summarized and sent to the ASBR in an external region. The LSA is generated by the API and a route entry pointing to the ASBR location, is the only route entry of the host in OSPF. External LSA: the routing information generated by the ASBR that is re-distributed into the OSPF region by the external routing protocol. NSSA external LSA: An LSA that can only exist in The NSSA region. Only ASBR can be redistributed to the NSSA region. The LSA of Type 7 can be converted to the LSA of type 5 and sent to other routing regions. 09. What types of OSPF paths are available? And detailed description? O: routing o ia in a region: routing information between regions O E1: External routing information. The measurement value is the external measurement value plus the measurement value from the local router to the ASBR. O E2: External routing information. The measurement value is an external measurement value, not an absolute value. O N1 :( NSSA) refers to the external routing information that is re-distributed. The measurement value is the external measurement plus the metric O N2 (NSSA) from the local router to the ASBR, the measurement value is an external measurement value, not an absolute value. 10. What types of OSPF media are available? Point-to-Point Access Point to multi-point access to non-broadcast link Request Routing 11. What do the three Bits V, E, and B in the router LSA mean? Virtual links, ASBR, and ABR12. which of the following statuses of OSPF neighbor routers start to select DR/BDR? In the 2-WAY status, select DB/BDR. 13. What is the role of DR/BDR? Easy to control network management and reduce Network Flooding 14. What conditions should be met when OSPF neighbors are established? Region ID, vroid ID, subnet mask, HELLO timer, authentication type and key, link type, 15. Which authentication methods does OSPF support? 1. No authentication method 2. Simple plaintext authentication 3. MD5 authentication. 16. What is the role of router-ID in OSPF? What are the vroid-ID options? A unique identifier of a vro in a region. You can manually set the router-id to configure the loopback interface as the router-ID. When there are multiple loopback interfaces, select the one with the largest IP address as the router ID. If there is no loopback interface, select the maximum IP address on the physical interface as the router ID, but the interface must be UP. 17. what are the advantages of using LOOKPACK as a router-ID? In addition to being a router-ID, what advantages does LOOKPACK have? Easy to control and stable. It can also be used as an unnumbered address. 18. What will happen if the authentication does not match between links? If the links are not in the same region, will they form an adjacent relationship? The two routers do not form a neighbor relationship, but the areas do not match and cannot form an adjacent relationship. 19. What is a routing domain? Use the same routing protocol to manage the set of routers in a unified domain. 20. What commands or types of modifications are configured for OSPF in the default fr nbma environment, and the relationship between routers is formed? In general, OSPF is in the default environment of NBMA. The interface type is not broadcast. You must manually specify the neighbor to establish the neighbor relationship normally. Run the "neighbor ip-address" command. If you do not need this command, you can also modify the interface type. In this way, the adjacent relationship can also be established normally. 21. What is the multicast address sent to the router in OSPF? What is the multicast address sent to DR/BDR? What if no broadcast is available in FR or ODR? The former is 224.0.0.5, and the latter is 224.0.0.6, which cannot establish a neighbor relationship. 22. What is stub? Peripheral Area: The summary LSA is introduced from other areas. The default route is introduced as a route summary, and the external LSA is not introduced. 23. What are the differences between STUB, NO-STUB, and NSSA? All are in the same end area STUB: The ending area. External LSA cannot be introduced in this area. The default route is introduced as a summary LSA. NO-STUB: completely ending area. External LSA cannot be introduced in this area, and summary LSA cannot be introduced. In this area, there are only one and two types of LSA, however, a default route LSA can be introduced as three types of LSA. NSSA: Non-completely ending area. External LSA cannot be introduced in this area, but there are seven types of LSA which are redistributed by ASBR. The seven types of LSA can only be in The NSSA area, it cannot exist in other regions. However, nssa asbr or nssa abr can convert LSA of the seven classes into LSA of the five classes and send it to other regions. 24. Why is the route table derived from the same LSDB in the same region in OSPF? There are five types of OSFP groups: the first is the primary HELLO data packet, the two sides establish a neighbor relationship, and the second is the description data packet of the database. During this period, the master and slave devices are selected and route information is exchanged, therefore, the LSDB in the same region is the same, in order to select an optimal non-ring path. At the same time, it also carries a lot of LSA header information, when a router does not have this LSA in its own routing information library, it sends a link status request. The route table is calculated based on the SPF algorithm. 25. What is the role of virtual links in OSPF? It is mainly used to fix discontinuous regional connections. This is mainly a design problem, so the design area is actually a bad design. 26. What are link IDs and advertised router IDs? What are their differences with router IDs? In OSPF, DR and BDR are only attributes of an interface or port, rather than a router. The link ID is used to identify the link. In router LSA, the link ID is the router ID. A Router ID is the router ID that advertises the route. They are the same as the router ID in a special LSA. 27. Can the MTU at both ends establish a neighbor if it does not match? If a neighbor can be established, what kind of status will the neighbor be in? The establishment of OSPF neighbors does not involve MTU information, but the establishment of OSPF neighbors may be affected. It may cause the neighbor to stop in the EXSTART/EXCHANGE status. 28. How does OSPF ensure reliable data transmission? OSPF uses a reliable mechanism such as inspection, serial number, and aging time to ensure reliable data transmission. Link status confirmation is also one of them. 29. If a port is closed, Will OSPF notify the route information on this port? If an interface is not started, will the OSPF process start? No. OSPF does not advertise the route entry information on the disabled port. If no interface is started, OSPF cannot be started. 30. Will OSPF advertise an interface address when it is configured with a layer-2 address? Under what circumstances? This depends on what the situation is. If the L2 address and the primary address do not belong to the same region, OSPF will not advertise the L2 address, if the L2 address and the primary address are in the same region, OSPF will advertise the route entry information. 31. If an ABR is not connected to Zone 0, will this generate four types of LSA? No. An ABR must be connected to Region 0. It is not connected to Region 0 and cannot generate four types of LSA.