CCNA Routing
Layer 3 devices are generically referred to as routers. Routers are two main functions:
1st If, after a layer-3 route to a destination network
2nd In order to get packets from one interface to another, a packet to its destination
To achieve the first function, a router:
– More on this router is to know networks that get connected
– Find places destination network numbers
– Select abest route for each destination
– Time, the best information on how to reach routing destination networks
Types of routes
A router can learn a route through one of two methods: static and dynamic. A static route is a route that is manually configured on the router. Dynamic routes are routes that a router learns by using a routing protocol. Routing protocols learn routes from other adjacent routers running the same routingProtocol.
Administrative distance
Remote Administration classifies IP routing protocols, assign a value or weight of each log. The distances can vary from 0 to 255. A shorter distance is more credible by a router, with the best distance 0 and the worst, 255
Static Route Configuration
Router (config) # ip route destination_network_ # [subnet_mask] IP_address_of_next_hop_neighbor
[Administrative_distance]
or
Router (config) # ip routedestination_network_ # [subnet_mask] interface_to_exit [administrative_distance]
Default Route Configuration
A default route is a special kind of static route.Where a static route is a path must use a router to have a goal to achieve a default route a path that must use the router if you do not know how to achieve your goal.
Router (config) # ip route 0.0.0.0 0.0.0.0 IP_address_of_next_hop_neighbor] administrative distance [
O
Router (config) # iproute 0.0.0.0 0.0.0.0 interface_to_exit [administrative_distance]
Dynamic routing protocols
dynamic routing protocols know the destination network from neighboring routers. dynamic routing protocols fall into three categories: distance vector, link-state and hybrid. Because of the differences between different types of routing protocol has advantages and disadvantages of each.
Distance Vector Protocols
Distance vector protocols are simpler. Distance VectorRouting protocols use distance and direction (vector) can be found at the destination. Most distance vector protocols use the Bellman-Ford algorithm for finding routes into the net. Examples of IP routing protocols RIPv1 and IGRP are distance vector. Distance vector protocols use periodic local broadcasts with a destination IP address 255.255.255.255 to share routing information.
Processing Updates
If a distance vector protocol receives aRouting updates, leads to the following steps:
1st Improve the metrics of incoming routes in advertising (for IP
RIP, add 1 to the number of hops).
2nd Compare the number of network routing update from neighbor
What has the router in its routing table.
3rd If the information is the neighbor better, put it in the routing table, and remove the old entry.
4th If the information of the neighbor who is worse, ignore it.
5th If the information in the vicinity of the exactsame entry already in the table, the timer for the entry in the routing table (in other words, the router already have learned this from near the same place).
6th If the information is added near a different location in a network of well-known tourist destination, but with the same metric as the existing network in the routing table, the router's routing table with the old. This assumes you have not exceeded the maximum number of equal cost paths to this goalNetwork number.
The six phases are commonly referred to as Bellman-Ford algorithm.
Link state protocols
Link state protocols use an algorithm called Shortest Path First (SPF) algorithm invented by Dijkstra to find the best route to a destination. Examples of IP protocols include OSPF Link State. While the distance vector protocols use local broadcasts to use routing information to propagate link-state protocols multicast. A protocol for sending its routing distancereligiously on his table at regular intervals, whether there are changes or not. Link protocols have been smarter. You Multicast what a Link State Advertisement (LSA), a piece of routing information that includes the announcement that they were formed and what is the network number. LSA is usually generated only when there are changes in the network. send link-state routers only incremental updates. Advantage that the link-state protocols are compared to distance vector protocolsthat support classless routing path [VLSM].
Hybrid protocols
A hybrid protocol takes the advantages of both protocols distance vector and link-state and merging into a new protocol. Typically, the protocols based on a hybrid distance vector protocol, but included many of the features and advantages of link-state protocols. Examples of hybrid protocols include RIPv2, EIGRP.
Problems with distance vector protocols
Problem: Convergence
The term convergenceRouting concepts, refers to the time to understand for all routers, the network topology. Link state protocols tend to converge very quickly, while the distance vector protocols tend to converge slowly.
Solution: Triggered Updates
You actually have two solutions that are used to accelerate the convergence: Change the interval timer periodically and / or deferred updates.
Problem: routing loop
A routing loop is a ring made of three layers of the network.This is fundamentally a disagreement about how to reach a destination network. Packet-loops in the network.
Solution: Maximum number of hops: IP RIP To a hop count limit of 15, by default, enables IGRP hop count of 100
Solution: Split Horizon
Split Horizon is used with small rings routing. Member Split Horizon, that if a router sends a location right next to a router, the router will not spread this way back to the router the same advertisingInterface.
Solution: Route Poisoning
The split horizon is used to solve the small problems of routing loops, distance vector protocols use two mechanisms to deal with the great problems of routing loops: route poisoning and hold timers. Route poisoning is a derivative of Split Horizon. When a router detects that one of his courses online is failed, the router poison way through the assignment of an infinite metric it. In IP-RIP, the route is a hop count of 16 (15 is the assignedMaximum), so that a network not reachable.
If a router is a route to its neighbors willing announces to its neighbors to break the rule of split horizon and return the same route poisoning, poison reverse are called. This ensures that everyone has the update get poisoned the original path.
Hold Down Timer
To the router enough time to distribute the route poisoning and to ensure that no routing loops occur, is occurring in the propagation giveA mechanism for the router down. During this time, the router will block the path to their routing tables for the period of the hold-down timer, usually three times the update interval of transmission routing poisoned. 180 sec
RIP (Routing Information Protocol)
IP RIP (Routing Information Protocol) is available in two versions: 1 and 2 Version 1 is a distance vector protocol. Version 2 is a hybrid protocol. RIPv1 uses local broadcasts to share routingInformation. These updates are regularly observed in nature, that by default every 30 seconds with a hold-down period of 180 seconds. Both RIP versions use hops as a metric to use is not always the best metric. RIPv1 is a classful protocol. Another interesting feature is that RIP supports up to six equal cost paths to a single goal. The default value is actually four tracks, but this can be increased to a maximum of six.
RIPv2
A marked improvement report RIPv2how they are routing updates. Instead of broadcast, multicast uses RIPv2. And to accelerate the convergence, RIPv2 supports triggered updates when a change is a RIPv2 router to propagate routing information immediately connected to their neighbors. A second major innovation is that RIPv2 is a classless protocol. RIPv2 support Variable Length Subnet Masking (VLSM), you can use to more than one subnet mask for a network of specific classNumber.
Configuring IP RIP
Router (config) # router rip
Router (config-router) # # Network IP_network_
Specifies RIP Version 1 and 2
Router (config) # router rip
Router (config-router) # version 1 | 2
Troubleshooting IP RIP
Show IP Protocols
show ip route
debug ip rip
debug ip rip
IGRP (Interior Gateway Routing Protocol)
The Interior Gateway Routing Protocol (IGRP) is a Cisco proprietary protocol, IP routing. As IP RIPv1 is a distanceVector protocol. However, scales better than RIP because these benefits:
– It uses a sophisticated metrics based on bandwidth and delay.
– It uses triggered updates to speed up the convergence.
– Supports the uneven load distribution costs for a single target. IGRP uses a composite metric, MTU includes bandwidth, delay, reliability, load, and in the choice of a route to a destination. By default, the algorithm only the bandwidth and Delay
Configuring IP IGRP
Router (config) # router igrp # autonomous_system_
Router (config-router) # # Network IP_network_
Unlike RIP, IGRP understand the concept of an autonomous system, and requires that you configure the autonomous system number in the routing process. have to share routing information for routers to be the same.
Load Balancing
With RIP, there is no need to load, configure, not cost, it has the same> Balance and RIP do not cost supports load-balancing uneven. IGRP supports both peer-and-paths of unequal cost load balancing to a single goal. equal cost paths by default, where IGRP supports up to six equal cost paths (four standard) is enabled for a single goal in the IP routing table. IGRP, but also support unequal cost path, but this feature is disabled by default.
The variance function allows you to include equality andIGRP unequal-cost routes in the routing table.
Router (config-router) # variance multiplier
Troubleshooting IP IGRP
Show IP Protocols
show ip route
debug ip igrp events
debug ip igrp transactions
OSPF (Open Shortest Path First)
The Open Shortest Path First (OSPF) protocol is a protocol that link-state routing for IP traffic management. Because it is based on an open standard, OSPF is very popular today in many corporate networks, and has many benefits, includingthese:
– Will run on multiple routers, since it is based on an open standard.
– Use the Dijkstra SPF algorithm was developed to provide a loop-free topology.
– Provides triggered a fast convergence, incremental updates from the Link State Advertisement (LSA).
– It is a classless protocol, so that a hierarchical design with VLSM and route summary.
Because of its advantages, has its share of disadvantages OSPF:
– OSPF operates three types ofTables. Chosen required more memory to the proximity (the list of OSPF neighbors Store) topology (a link-state database of all routers and their routes), and routing tables.
– Requires extra processing on the CPU to the SPF algorithm, then, especially if you will first run on the router, and are initially build the topology and adjacency tables.
– For large networks, requires careful planning to break the network into a corresponding hierarchySeparation routers in different areas.
– It is easy to configure complicated and difficult to solve.
Hierarchical Design: Areas
The areas are used to provide hierarchical routing. Basically, the spaces are used to release control when and how the routing information for the network. Dish Network design, such as IP RIP, if a change occurs on a router, maybe a problem of route flapping hitting, each router on the network. Designed with the correct hierarchicalNetwork requires that changes be included in the room. OSPF implements a two-level hierarchy: the backbone (area 0) and areas off the spine. Through proper design of IP addressing, you should be able to summarize the routing information between areas. Running this list routers have a database of smaller topology (who knows, only the links in your area and the summary routes) and their routing tables are smaller (who knows only of its area and routesAbstract routes).
Metrical structure
In contrast to RIP, the hop count metric used as a cost, OSPF uses. The cost is actually the inverse of the bandwidth of a connection: The faster connection speeds, lower costs. The most preferred route is the lowest cost. The use of cost as a metric is to choose the route most intelligent OSPF RIP. OSPF supports load balancing with up to six equal-cost paths to a single goal. The standard measurementCisco used to calculate the cost is, metrics: Cost = 10 ^ 8 / (bandwidth interface).
Router Identity
Each router in an OSPF network needs a unique ID. The ID is used to provide an identity, the OSPF router. This is generated in all messages OSPF router included. The router ID is selected by one of the following criteria:
– The highest IP address on its loopback interfaces (This is a logical interface on a router)
– The IP address to its highestactive interfaces
We strongly recommend that you make a loop back interface for it is always high, and then you can get a router, the router ID.
Find Neighbors
OSPF learns its neighbors and builds its adjacency matrix and topology tables LSA-sharing. There are different types of LSA. When neighbors know that a router is connected and Controlling know the neighbors, OSPF routers will generate LSA Hello every 10 seconds. If a neighbor isdiscovered and formed a co-existence with its neighbors, a router expects to see leave next hello. If the neighbor within the dead time, the view defaults to 40 seconds, the neighbor is declared dead. If this happens, the router this information by e-LSA will be published to other routers OSPF neighbors. In order for the two routers with the neighbors, they must pay for each router:
– The number of the region and its nature
– The Hello andDead Interval Timer
Let's say you turned on all the routers simultaneously on a segment. In this case, OSPF routers through three states pass called Exchange Process:
1st Down was the new router has no information exchanged with other OSPF routers.
2nd Init was a target router has received a new router Hello and adds his list next (assuming certain values match). Note that the communication is only one way thisPoint.
3rd Two-Way was the new router to get a response one way for his initial Hello packet and adds the destination router in addition to its database. Once the routers are entered in a two-way state, they are regarded as neighbors. At this point in an election process takes place to select the designated router (DR) and backup designated routers (BDR).
Designated Router and Backup Designated
An OSPF router is not next to each router. Instead, aClient / server design is implemented in OSPF. For each multi-access network segment, there is a DR and BDR as well as other routers. When an OSPF router appears to form adjacencies with the DR and BDR on each multi-access segment, which is connected. Any exchange of information between these routing / DR and BDR routers other OSPF neighbors on a segment (and vice versa). An OSPF router on a DR with the multicast IP address of 224.0.0.6. The DR and BDR all speakRouter with IP multicast address 224.0.0.5.
The OSPF router with the highest priority is the DR for the segment. If there is a tie, the router with the highest Router ID is the default, all DR router a priority of 1 (priority can 0-255 range). If the DR fails, the BDR is promoted to DR and other router is elected as BDR. OSPF use incremental updates. This means that when changes occur only with the transmission of the DR, which is dividedShare this information with other routers on the route. Exchange of information on their routes OSPF routers connected to the DR, including the type of link-state ID of the router advertisement, the cost of the advertised link, and the sequence number of the connection.
Configuring OSPF
Router (config) # router OSPF PROCESS_ID
Router (config-router) # area network ip_address wildcard_mask area_ #
Note that the process ID does not match between different routers andhave nothing to do with numbers autonomous system.
A wildcard mask is 32 bits long. A 0-bit in position "means that it will be a game, and a 1 bit in position": The router does not care. In fact, a wildcard mask is a netmask is inverted mode with 1 and 0.
Class A: 0,255,255,255,255
Class B: 0.0.255.255
Class C: 0.0.0.255
Loopback Interfaces
A loopback interface is a logical, virtual interface on a router. By default, your routerFor each loopback interface, but can easily be created. Here are some reasons why you are able to create a loopback interface:
– To assign an ID to the router OSPF Router
– To be used for testing, because this interface is always
To create a loopback interface, use the following command:
Router (config) # # loopback interface port_
Router (config-if) # ip address ip_address subnet_mask
Troubleshooting OSPF
• Show IP
• show ipRoute
• show, OSPF IP interface
• OSPF neighbor show ip
• Debug IP OSPF adj
• debug ip OSPF events
• Debug IP OSPF packet
EIGRP (Enhanced Interior Gateway Routing Protocol)
The Enhanced Interior Gateway Routing Protocol (EIGRP) is a proprietary protocol of Cisco IP routing. It is actually based on IGRP, worked with many improvements. These functions include:
– Fast convergence
– Loop-free topology
– VLSM and RouteCompression
– Multicast and incremental updates
– Routes for most routing protocols (support IP, IPX, AppleTalk)
Features of EIGRP
Both offer load-balancing by six (equal or unequal).
– You have similar metrical structures.
– EIGRP convergence is faster (activated upgrades, and savings from a nearby
Routing table local).
– EIGRP network has less overhead because it uses incremental updates.
IGRP and EIGRP usethe same metrical structure. Both can be bandwidth, delay, reliability and MTU in the calculation of metrics best route to a destination. By default, only bandwidth and delay in the metric calculation can be used. An interesting point of these protocols is that if you have some routers in the network running IGRP and EIGRP to run another, and both have the same number of autonomous system, routing information is automatically shared between the two.
EIGRP uses the Diffusing UpdateAlgorithm (DUAL) to update the routing table. This algorithm can be a very fast convergence, the storage of routing information, a neighbor in a local topology table. If a primary path fails in the routing table, DUAL a backup path from the topology table and paste it into the routing table without talking to other EIGRP routers close to an alternative route to your destination to . find
Interaction with other EIGRP routers
EIGRP uses Hello packetsto discover and maintain neighbor relationships, like OSPF does. EIGRP Hello packets generated every 5 seconds on the LAN, Point to Point and Multi Point, with a speed T1/E1 rates. Otherwise, hellos are generated every 60 seconds. The time interval died three times the Hello interval. EIGRP uses multicast address 224.0.0.10 to the target in the Hello packets.
For routers EIGRP neighbors become the following information must match:
– ASNumber
– The values of K (this activation / deactivation of the various metric components)
When two routers to determine if they are neighbors go through the following procedure:
1st The first router generates a Hello configuration information.
2nd If the configuration information matches, the second router responds with an update message with topology information.
3rd The first router responds with an ACK, the acknowledgment of receipt of the second ACK.
4thThe first router sends its topology to the second router via an update message.
5th The second router responds back with an ACK.
At this point, the two routers are converging.
Here are the types of messages for which an EIGRP router expects an ACK:
– Update contains a routing update
– Query asks for a neighboring router, check the routing information
– Answer requests by
If an EIGRP router receives no ACK from these three types of packagesThe router will send a total of 16 times the information again. Thereafter, the router declares the neighbor dead. When a router sends a Hello packet, there is no corresponding ACK.
Configuring EIGRP
Adjusting EIGRP is almost as easy as configuring IGRP:
Router (config) # router # EIGRP autonomous_system_
Router (config-router) # # Network IP_network_
You must specify the number as in the configuration of EIGRP. Although EIGRP is classless, it is necessary
configure it asclassful a protocol when you specify your network numbers, with the command network.
Troubleshooting EIGRP
– Show IP Protocols
– Show ip route
– Show ip eigrp neighbors
– Show ip eigrp topology
– Show ip eigrp traffic
– Debug ip EIGRP
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