Parsing of EIGRP Protocol

I. Basic OVERVIEW:

1.EIGRP is a Cisco private-----supports large networks

2. The king of convergence, very fast

3. Enhanced Internal Network routing protocol, is a hybrid routing protocol

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

Two. Basic Features:

1.OSI Hierarchy: Transport layer protocol, based on IP protocol number 88

2. Algorithm features: Distance vector (DUAL algorithm, Dispersion correction algorithm )

3. Operating range: Internal Gateway Protocol

4. There are classes without classes: IGRP is a class, EIGRP is no class

5. Best path: Manage distance 90/170, measure in 5 cases (bandwidth, latency, load, confidence, MTU)

(Baidu, new)

6. Routing Update: Use multicast (224.0.0.10) By default for routing updates, or to support unicast updates

Three. EIGRP's neighbor Establishment

Table entries for 1.EIGRP

① Neighbor Table

Used to store neighbor information show ip eigrp neighbor

② topology Table

Used to store all (all possible) routing entries (regardless of pros or cons) show ip eigrp topology (all-links)

③ routing Table

Used to store the best route entry (computed by the dual algorithm) show IP route eigrp

2.EIGRP Routing Grouping

①hello Grouping

Function: Used to establish and maintain neighbor relationships, send every 5s cycles, 15s hold Time (hold-time)

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

When the bandwidth is greater than 1.544M, the period is 5s and the retention time is 15s;

Hold-time==hello time

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②update Grouping

Features: Used to host and deliver routing entries, update packages, and send routing update information. (If you do not receive an ACK confirmation, it will be re-issued 16 times, 16 times, after the disconnection of the neighbor relationship)

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③query Grouping

Query package: When the router loses its original route, it sends a "query request" to the neighbor.

④reply Grouping

When the router is queried and receives a "query request", it responds to the routing information it knows to the originating query router.

⑤ack Grouping

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

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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 that is larger than the T1 (1.544Mbps) Link, the default is 5 seconds to send a Hello packet. On a multipoint link less than/equal to T1, the default is 60 seconds to send a Hello packet.

②hold Timer

The Hold timer is 3 times times the default for the Hello Timer , and if the hold timer is defined for a time that does not receive the other's Hello packet, the neighbor relationship will reset.

Four, EIGRP Route rollup

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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

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Null0 This interface is the virtual or spoofed interface of the router, which is permanently in the up state, cannot be encapsulated and forwarded traffic, and is primarily intended to prevent routing loops from occurring in the EIGRP rollup.

The route that points to the Null0 interface is that the router itself generates a summary segment and advertises it to its neighbors to reduce the size of the routing table.

How is the Null0 anti-ring?

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①R1 's IP address is summarized as 192.168.0.0/22

②r1 to tell R2 the aggregated information

③ R2 Update routing table: D192.168.0.0/22--->f2

Default routes are default on ④R1 routers: 0.0.0.0

⑤ at this time the intranet has host Ping 192.168.3.1 (default)

⑥

Assuming that R1 does not produce a route table to Null0 at this point, 192.168.3.1 is advertised by the default route and arrives at R2, because R2 has a 192.168.0.0/22-->F2 routing table, and R2 returns the ping packet to R1, which causes the loop.

With a routing entry pointing to Null0, you can avoid loops. Packets that match to this route entry are discarded into the null0 (data black hole), which is discarded by the router and will not be sent out.

Null0 routing is better than the default route.

Summary:

①null0 routing is used to resolve routing loops.

② network subnets are sometimes incomplete, but the aggregated route is still communicated to the neighbor, which can cause a routing loop if the network topology has a packet with a "missing subnet".

③null0 route priority is higher than the default route, which effectively prevents data from being forwarded and suppresses data locally.

Add:

5 Standards for EIGRP metric

Bandwidth (bandwidth)

10 of the 7 divided by the lowest bandwidth between the source and the target multiplied by 256 (10 of the 7 squared divided by the minimum bandwidth in kbit/s, then the sum of the delay divided by 10, and the last multiplied by 256)

Latency (delay)

The cumulative delay of the interface is multiplied by 256, in units of 10 microseconds

Reliability (Reliability)

The most unreliable reliability value between source and destination based on KeepAlive

Load (Loading)

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

Maximum Transmission Unit (MTU)

The smallest mtu.mtu in the path is included in the routing update for EIGRP, but generally does not take part in the arithmetic of EIGRP degrees

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Parsing of EIGRP Protocol