Shulou(Shulou.com)06/01 Report--

1. eigrp profile

EIGRP is a private routing protocol invented by Cisco, developed from IGRP, but the algorithm has been greatly changed.EIGRP, IGRP and RIP are dynamic routing protocols using D-V algorithm, which have great improvements in convergence speed, network bandwidth and system resources, and have the advantages of fast convergence and loop-free routing calculation, which can be applied to large-scale networks.

RTP: EIGRP packets are delivered to all neighbors in sequence. It supports mixed transmission of multicast and unicast packets. Multicast packets are sent without response, and unicast packets are sent instead.

dual algorithm: Ensure no loop, can achieve multiple paths Load Balancer;

2. establish a neighbor

·Conditions

hello packet transmission interval

eigrp establishes neighbors through hello packets. To establish neighbors, conditions are required:

1) consistent as number 2) same K value 3) same authentication etc. 4) network segment 5) unicast multicast consistent

3. three tables

There are three tables in eigrp: neighbor table, topology table and routing table:

Neighbor table: View neighbor relationships;

Topology table: active route and standby route are in topology table;

Routing table: the best route is added to the routing table;

address: IP address of neighbor

interface: Establish the interface of the neighbor

Hold Uptime: Neighbor Establishment Time

srtt: the time the other party is responding to the ack packet

rto: how much time has elapsed

Q: Queue during congestion

seq num: Sequence number of message, used for confirmation mechanism

What are srtt and rto?

Reliable messages are retransmitted if they are not answered by neighbors some time after they have been sent. After 16 retransmissions, if there is no response, the neighbor is reset.

The time period between the transmission of a message and the retransmission of the message is called Retransmit Time Out (RTO).

Calculation method:

1. Each time a message is successfully sent, RTO is calculated based on the round-trip time of the message as follows (in milliseconds):

RTT(Round Trip Time): The time required from the time a message is sent to the time an ACK is received.

SRTT(Smoothed Round Trip Time, average estimate of round trip time), for each ACK received:

SRTT(new)=0.8*SRTT(old)+0.2*RTT

RTO(Initial)=6*max(SRTT,PacingInterval)

That is, in general,RTO is 6 times SRTT.

2. After each retransmission due to RTO timeout, the retransmission time will be longer and longer. The next retransmission time is:

RTO(New)=RTO(Old)*1.5

RTO(Final)=min(5000,Max(200,RTO(Computed)))

That's RTO times 1.5, but 200 milliseconds minimum, 5 seconds maximum.

·Topological tables

The topology table contains the optimal path and the backup path. When the optimal path has a problem, the backup path does not need to be calculated directly into the routing table.

FC algorithm is needed to satisfy standby path;

·Routing tables

the optimal path calculated in the topology table is added into the routing table;

4. packet composition

EIGRP has 5 types of packets: hello, update, ack, query, reply,

5.eigrp metric

The metric of eigrp is related to bandwidth, delay, reliability, load and mtu, where FD is calculated as bandwidth + delay:

metric=(10^7/min bandwidth + delay sum/10)*256

metric(A B C D)=(10000000/64+6000/10)*256 =40,153,600

metric(A X Y Z D)=(10000000/256+8000/10)*256=10,204,800

Because metric(A B C D)>metric(A X Y Z D), it is better to choose A X Y Z D path;

The show interface command is used to view port status:

BW: Bandwidth

DLY: Delay

reliability: reliability (default 255) is the most reliable, if there is a bit error rate will be reduced;

load: divided into txload send rxload receive;

txload The packet load. The higher the load, the higher the value (default 1). Congestion may occur when it reaches 255/255.

rxload Packet load. The higher the load, the higher the value (default 1). Congestion may occur when it reaches 255/255.

MTU: Maximum Transmission Unit (default 1500);

6.eigrp routing summary

Default automatic route summary, summarized into the main class route;(normal use must be closed);

·Automatic filtering of fine routes when aggregated

Configuration:

interface FastEthernet0/0

ip summary-address eigrp 1 3.3.0.0 255.255.0.0 5 \\summary 3.3.0.0/16, ad is 5

Pre-summary routing table:

Summarized routing table:

·Aggregated time through fine routing

Configuration:

interface FastEthernet0/0

ip summary-address eigrp 1 3.3.0.0 255.255.0.0 5 leak-map guolv

\\Summary 3.3.0.0/16, ad = 5, route-map call = guolv

route-map guolv permit 10

match ip address 1

access-list 1 permit 3.3.3.3

Pre-summary routing table:

Summarized routing table (summarized, detailed routing through 3.3.3.3)

7.eigrp Load Balancer

eigrp has equivalent Load Balancer and non-equivalent Load Balancer;

Equivalence Load Balancer: FD values for several links that are identical

Non-equivalent Load Balancer: 1. Standby link satisfies FC condition FD1> AD2; 2. Variation satisfies FDmax/FDmin rounded up;

Example 2

·Alternate paths

FD(C) is the best path, FD(C)>AD(standby)

1. FD(C)20>AD(B)10 satisfies FC condition

2. FD(C)20

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