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

I. Basic overview:

1. EIGRP is Cisco Private----Support for Large Networks

2. King of convergence. Very fast.

3. Enhanced Internal Network Routing Protocol, a hybrid routing protocol

4. Reliable updates, triggered updates, incremental updates, multicast updates

II. Basic features:

OSI Layer: Transport Layer Protocol, based on IP Protocol Number 88

2. Algorithm characteristics: Distance vector (DUAL algorithm, dispersion correction algorithm)

3. Scope of operation: Interior Gateway Protocol

4. Classless: IGRP is classful, EIGRP is classless

5. Best Path: Management Distance 90/170, metric values in 5 cases (bandwidth, latency, load, reliability, MTU)

(100% added)

6. Route update: multicast (224.0.0.10) is used by default for route update, unicast update can also be supported

3. Neighbor Establishment of EIGRP

1. EIGRP entries

① Neighbor list

Used to store neighbor information show ip eigrp neighbor

② Topological table

Used to store all (all possible) route entries (good or bad) show ip eigrp topology (all-links)

③ Routing table

Used to store the best route entry (calculated by the DUAL algorithm) show ip route eigrp

2. EIGRP routing packets

1 Hello group

Function: Used to establish and maintain neighbor relationship, send every 5 s cycle, 15s hold-time

===> When the bandwidth is less than 1.544M, the period is 60s and the holding time is 180s;

When the bandwidth is larger than 1.544M, the period is 5s and the holding time is 15s;

hold-time==hello time *3

②Update grouping

Function: Used to carry and deliver routing entries, update packets, and send routing update information. (If no ACK acknowledgement is received, it will be retransmitted 16 times, and after 16 times, the neighbor relationship will be disconnected)

③Query grouping

Query packet: When a router loses its original route, it sends a query request to its neighbors.

④Reply grouping

When the queried router receives the query request, it responds to the query router with the route information it knows.

5 Ack packet

Used to confirm reliable transmission of EIGRP messages. (equivalent to receipt)

R1#sh ip eigrp neighbors----View neighbor table

R1#sh ip eigrp topology ------View topology table

R1#sh ip eigrp topology all-links----View topology table

3. EIGRP Timer

①Hello Timer

On a point-to-point link, the default is to send a Hello packet once every 5 seconds. On multipoint links less than or equal to T1, Hello packets are sent once every 60 seconds by default.

②Hold Timer

Hold timer is 3 times of Hello Timer by default. If no Hello packet is received within the time defined by Hold Timer, the neighbor relationship will be Reset.

IV. EIGRP routing summary

interface Loopback2

ip address 172.16.1.1 255.255.255.0 secondary

ip address 172.16.2.1 255.255.255.0 secondary

ip address 172.16.3.1 255.255.255.0 secondary

ip address 172.16.0.1 255.255.255.0

router eigrp 90

network 1.1.1.1 0.0.0.0

network 12.1.1.0 0.0.0.255

network 13.1.1.0 0.0.0.255

network 172.16.0.0

no auto-summary

Summary Configuration:

R1(config)#int range f0/0 , f1/0

R1(config-if-range)#ip summary-address eigrp 90 172.16.0.0 255.255.252.0

Null0:

Null0 This interface is the virtual or disguised interface of the router. This interface is permanently up and cannot be encapsulated and forwarded traffic. In the summary of EIGRP, it is mainly to prevent routing loops from occurring.

Routes pointing to the null0 interface are generated by the router itself and advertised to its neighbors to reduce the size of the routing table.

How is Null0 protected?

① The IP address summary of R1 is 192.168.0.0/22

②R1 tells R2 the summary information

③R2 updates routing table: D192.168.0.0/22--->F2

④R1 router has default route by default: 0.0.0.0

④ At this time, there is a host in the intranet ping 192.168.3.1 (default)

⑥

Assuming that R1 does not generate a routing table pointing to Null0 at this time, 192.168.3.1 will be advertised by the default route to R2. Since R2 has a routing table of 192.168.0.0/22-->F2, R2 will return a ping packet to R1, which will cause a loop.

A route entry pointing to Null0 prevents loops. When a packet matches this route entry, it is dropped into null0 (data black hole), which is discarded by the router and not sent out.

The null0 route is superior to the default route.

Summary:

①Null0 route is used to solve routing loop

② Sometimes the network subnet is incomplete, but it will still inform the neighbors of the summary route. If there is a packet passing through the "missing subnet" in the network topology, it may cause a routing loop.

The null0 route has higher priority than the default route, which can effectively prevent data from being forwarded and suppress data locally.

Additional:

Five criteria for EIGRP Metric

Bandwidth (bandwidth)

10 to the 7th power divided by the lowest bandwidth between source and destination multiplied by 256(10 to the 7th power divided by the minimum bandwidth in Kbit/s, then add the sum of delays divided by 10, finally multiplied by 256)

delay (delay)

Cumulative delay of interface multiplied by 256 in 10 microseconds

Reliability (reliability)

The value of the least reliable reliability between source and destination depending on keepalive

Load (loading)

The value of the least bad load between source and destination based on packet rate and interface configuration bandwidth

Maximum Transmission Unit (MTU)

The smallest MTU in the path. MTU is included in EIGRP routing updates, but generally does not participate in EIGRP metric calculations.

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