CCNP Advance EIGRP Features

Route summarization
EIGRP has the ability to auto summarize networks. However, if the networks are limited, you may want to disable automatic summarization. In order to do this enter the following command:
Router(config) # no auto-summary.
The limitation with auto summarization is that EIGRP is only capable of summarizing networks which are part of the network. Therefore, for these cases you have to input an auto summarization which the following command:

ip summary-address eigrp 100
subnet

Load balancing in Equal Cost Path

In an equal cost path, the links in the network have are symmetric which means they use the same circuit type and the same same bandwidth capacity, so the same cost is assigned to the each link.
Since both link have the same distance as well, the metrics for its destination is available, through these links which are equal. When EIGRP chooses the successor route, it wants to choose a link which is at the lowest cost. When it sees that the 2 path ways have the same metric then it chooses them as its successors. After this EIGRP will then be able to share the traffic loads across the multiple links, which is known as load balancing.

Load Balancing in Unequal Cost Path
Unequal cost load balancing is when traffic across multiple routes is balanced withing different metric routes. This load balance is done through the variance command.

Router(config-router) #
variance multiplier
In load balancing, the multiplier parameter the values from 1-128 are used. 1 is the default value where there is an equal cost for load balancing


Suppose we have a network with 3 path way
Path 1 has a metric of 10
Path 2 has a metric of 15
Path 3 has a metric of 30
The path which will be selected will be the first path since the metric is lowest in path 1. With EIGRP you have to select that path, and configure it with a variance of 2.
Once you multiply by path and variance then you will get a minimum variance of 20.
10 metric * 2 variance value = 20 minimum metric
EIGRP will includes all routes that have a metric of less than 20 and satisfy the workable condition. EIGRP will take both path one and two since their metric distance is less than 20. The 3rd path will not be taken since 20< 25.
Therefore, the load balancing will occur between path one and path two.
Bandwidth Utilization

Bandwidth needs to saved within networks, so the network performance can be enhanced. By default EIGRP is set to use up to 50 % of bandwidth within an interface for routing traffic. However, this can be changed by using the following command:
ip bandwidth-percent eigrp as-number percentage the as number is AS number and percent is percentage you want to input.

When configuring multipoint interfacess such as Frame Relay it is important to to set the bandwidth to equal to share it across the neighbors.

CCNP Basic EIGRP commands

The EIGRP process is identified by an autonomous system number. If the autonomous system numbers are the same within the routing domain, the routers will be able to exchange information. Otherwise, if the autonomous system numbers do not match then the routers will not be able to exchange information.

To Enable EIGRP the following command needs to be entered

Router (config) #
router eigrp autonomous-system-number

ie router eigrp 10

Next the network need to inputted

Router (config) #
network network number [wildcard mask]
i.e network 172.16.0.0 0.0.0.255
network 172.16.1.0 0.0.0.255

*A wildcard mask is used to connect a router to external router which is outside the autonomous system.



Next the bandwidth need to be set up. By default it is set at the speed of T1
If there are serial links then the bandwidth needs to be set up. The bandwidth is measure in kbps.


Router (config) #
bandwidth kilobytes


EIGRP default route can be enabled with the following command.

ip default-network ip address



Troubleshooting.

show – the show command can be used to trouble shoot

show ip eigrp neighbors

This command shows you if the neighbors within the routers are recognized



show ip route eigrp

shows all EIGRP routes


show ip protocols
shows all dynamic routing protocols enabled on the router

show ip eigrp interfaces
Thie command shows all the interfaces configured for EIGRP.

Fast Ethernet
Fa0/0
Serial
S0/0


show ip eigrp topology

This shows the status of the network.
P (passive) – Network is available
A(active) - Network is not available
U(update) Network is being updated
Q(Query) Requesting information from a neighbor
R(reply) Got a reply or needs a reply
S(struck in active status) There is a problem with the network


show ip eigrp traffic
To see if the packets are sent or received



For more options you can put a question mark after the show command

show ?

CCNP EIGRP Components

EIGRP Tables
DUAL uses the EIGRP tables, which are provided. Within the EIGRP tables you will find a neighbor table, a topology table and a routing table.

Here are functions each table performs.
Neighbours Table - shows all neighbours adjacent to router
Topology Table - shows all route entries learned by the router
Routing Table – shows the best route to get to other points on the network


EIGRP Packets

Uses Five Packet Types

Hello
Check if the neighbor is up
Update
Used to send routing updates
Query
Finds out information from neighbors regarding routing updates
Reply
This is where the neighbors give a response
Acknowledgement
If you send a message, it must be acknowledged by the person who receives it. This packet is used to acknowledge a reliable packet.
The above are five main packets EIGRP uses. However, EIGRP can also use a packet called request.

Request – This packet is used to get information for a specific route. The information is received from one or more neighbors. Therefore the methods to send a request can either be through a unicast or a multicast process.




EIGRP Metric
EIGRP uses the metric component.
Metric is a Calculation done by the Routing protocol to determine the best path through a network. Since EIGRP uses 32 bits for its calculation it is metric is multiplied by 256. Metric consists of 5 components which are bandwidth, delay, reliability, loading, MTU.

EIGRP Metric Calculation
Metric = bandwidth + delay

EIGRP uses two of the components of metric which are bandwidth and delay. In the bandwidth, the measurement is based on the smallest amount of consumed data between the source and destination. In delay the delays in the path is measured.

CCNP EIGRP Fundamentals

Enhanced Interior Gateway Routing Protocol (EIGRP) is an advanced distance vector protocol. However, it also has a hybrid routing protocol capability since it combines the best of a distance vector protocol with link state algorithms by using partial updates and neighbor discovery. From other distance vector protocols it offers improvements such as reduction of bandwidth use, fast convergence, support for classless subnets which use CIDR and VLSM, and support for multiple routed protocols like Apple Talk, IP and IPX.


Among the key feature of EIGRP the following are included:
1)Fast Convergence
2)VLSM Subnetting
3)Partial Update
4)Multiple Network Layer Protocol Support

Fast Convergence: EIGRP stores its neighbours routing table so it can take alternatives routes if it original route is gone. Also, it has the ability to ask its neighbours for alternative routes if needed.

VLSM Support: EIGRP uses classless subnets within it routing network. For classful major networks it automatically summarizes routes on the attached interfaces. EIGRP also support manual summarization, and for this it uses VLSM to force a summary route from an interface.

Partial Updates: Partial Updates contain information about the change routes, and they are sent when route need a change in its metric or path. They are handled by multicast or unicast packet instead of broadcast packets since it reduces the use of bandwidth.

Multiple Network Layer Protocol: EIGRP can support IP, IPX, and AppleTalk routed protocols which enable EIGRP to have good stability and high performance networks.


EIGRP has four unique key components.

1. Protocol-dependent modules: Responsible for requirements within the network layer protocols.
2. Reliable Transport Protocol (RTP) : Support Unicast and Multicast transmission. RTP's main role is to guarantee a a timely, reliable and efficiently. EIGRP reliable transport protocol (RTP) guarantees timely, reliable, and efficient exchange of routing data between EIGRP neighbours.
3. Neighbor Discovery and Recovery: Discovery and Recovery allow routers about the other routers that are attached on the network neighbor discovery and recovery enables routers to dynamically learn about other routers on their directly attached network . It does this by allowing EIGRP to build a neighbor table which shows all neighbors adjacent to the router, to a topology table which discovers routes and routing table which choses the best path.
   

4. Diffusing Update Algorithm (DUAL): DUAL is the heart of EIGRP. It relies on
protocols and data structures to provide all the routers in a network to lead up to the final route.

Reported Distance & Feasible Distance

Feasible Distance: The total path between a router and the next closest router + Sum of all cost.

Reported Distance is the distance (metric) towards a destination as advertised by an upstream neighbour.
Reported distance is the distance reported in the queries, the replies and the updates.
Reported Distance: The total path between a router and the next closest router

OSPF

• Dynamic Routing Protocol for IP Networks
• Link State Protocol
• Group of Interior Gateway Protocol
• Operates withing a single Autonomous System
• Conifgured with Wildcard Mask
• Process ID - Uses Dijkstra’s algorithm
• Network Types – point to point, and routers that are directly connected

RIPv2

• Distance Vector Protocol
• Supports classless routing protocol
• Authentication option available
• Uses multicast addresses in sending updates
• Sends subnet information in RIP header
• Supports authentication

Router Memory

RAM: The RAM stores the OS, running config file, IP routing table, Arp cache and packet buffer

ROM: Permanent storage – Scaled down version of IOS, Basic software

Flash Memory: Permanent storage of for OS, Cisco IOS

NVRAM: Used as permanent storage for startup config files.

3 Configuration Registry

0 * 2142 For password recovery.
0 * 2102 The default. Router looks for config file in NVRAM and for a valid IOS image.
0 * 2100 Router boots into ROM monitor mode.

4 types of Timers

Update timer: 90 seconds

Invalid timer: 270 seconds

Hold down timer: 180 seconds

Flush timer: 630 seconds

Feasible Distance & Successors

Feasible Distance: The total path between a router and the next closest router + Cost.
Successors is a neighboring router that has a least cost path to a destination.

5 types of LSP packets

1)hello (checks if neighbour is up)
2)Database Description (synchronize databases in the beginning)
3)Link State Request (Request Specific LSA)
4) Link State Update (LSA flooded)
5) Link State Acknowledgement (flooded LSA’s are exploited acknowledged reliable flooding)

Difference Between Reported Distance and Administrative Distance

Reported Distance is the distance (metric) towards a destination as advertised by an upstream neighbour. Reported distance is the distance reported in the queries, the replies and the updates.
Reported Distance → The total path between a router and the next closest router.

Admistrative Distance is a measure of the trustworthiness of the source of the routing information.

Roles Of A Router

DR – reduces the number of adjacencies required on a multi-access network, which in turn reduces the amongst of routing traffic and the size of the topological database.

BDR - A router that becomes the designated router if the designated router fails

DROther - The router with the highest priority becomes the designated router (DR). If the priorities are the same, then the router with the highest router ID becomes the DR. By default, priorities are set to 1. A router with a priority of 0 never becomes a DR or a backup designated router (BDR); it is always a DROTHER, meaning a router that is neither the DR or the BDR.

How is a router id assigned ?

The router-id is chosen based on the highest IP address present on the router. If a loopback interface is present, the loopback IP will be used. If more than one loopback interface is present, the highest loopback IP will be used.

What are Hello Packets used for ?

• To discover OSPF neighbours and establish neighbour adjacency.
• Advertise parameters on which two routers must agree to become neighbours.
• Elect DR and BDR on multi access networks

Difference between Metric and Administrative Distance ?

Administrative Distance determines what priority will be given to each Routing protocol redirected through a router.
Metric is a Calculation done by the Routing protocol to determine the best path through a network.

EIGRP Tables

Neighbours Table - shows all neighbours adjacent to router

Topology Table - shows all route entries learned by the router

Routing Table – shows the best route to get to other points on the network

OSPF Tables

Neighbours Table - shows all neighbours adjacent to router.

Topology Table - shows all route entries learned by the router.

Routing Table – shows the best route to get to other points on the network.

What makes EIGRP unique ?

• Uses Diffused Update algorithm (DUAL) for all route computation
• Uses multicast and unicast for sending packets
• Administrative Distance for Internal router is 90
• Administrative Distance for External router is 170

Link State vs Distance Vector Protocol

Link state transmits data based on the speed of the WAN link.
Distance Vector transmits data based on the cost of the link (usually based on hop count).

If start up config is not found in the RAM memory what does it do ?

It searches the NVRAM where all the it is permanently stored!

DR Selection Process

OSPF chooses the designated router (DR) on a LAN as the device that has the highest IP address. If routers are added or removed from the LAN, or if a router gains an interface with a higher address than that of the existing DR, the DR likely will change if the DR or backup designated router (BDR) fails.

Routing Table

A routing table contains the information necessary to forward a packet along the best path toward its destination. Each packet contains information about its origin and destination. When a packet is received, a network device examines the packet and matches it to the routing table entry providing the best match for its destination. The table then provides the device with instructions for sending the packet to the next hop on its route across the network.

A basic routing table includes the following information:

Destination: The IP address of the packet's final destination
Next hop: The IP address to which the packet is forwarded
Interface: The outgoing network interface the device should use when forwarding the packet to the next hop or final destination

Metric: Assigns a cost to each available route so that the most cost-effective path can be chosen

Routes: Includes directly-attached subnets, indirect subnets that are not attached to the device but can be accessed through one or more hops, and default routes to use for certain types of traffic or when information is lacking.

If the IOS fails what does it do ?

If the IOS fails what does it do ?

IOS is stored in flash memory or TFTP. It is then loaded into the RAM. If a full IOS image cannot be located, a scaled down version of the IOS is copied from ROM into Ram.

Routers

Layer 3 Routing

• Single broadcast domain per interface
• Every router is its own broadcast domain
• ACLs can be applied between segments

Issues

• High per-port cost
• Layer 3 processing required
• High latency over layer 2 switching
• Layers 3 processing happens in software

Nonhierchical Networks Issues

What wrong with Nonhierchical Networks ?

They have:

• Large collision domain
• Large broadcast domain
• High Latency- There is high latency because everyone of the repeaters is repeating the same packet

• Difficult to troubleshoot

Intelligent Information Network CCNP Module 1

IIN (Intelligent Information Network)

Integrates Network resources and information assets

Three phases in building in IIN are

1) Integrated Transport- All traffic which includes voice, data and video is put together into one IP address, so data which is sent can be secured on the network.

2) Integrated Services- After all the network resources have been gathered, the resources can be shared across the network.

3) Integrated Applications-In the third phase, the networks make the application active, so network capablities such load balancing, application level security, content caching makes the delievery and performnce more efficient for the users.