Shulou(Shulou.com)06/02 Report--

Routing Foundation

What is routing:

Routing: routing is the path information that guides the sending of IP messages

ICMP protocol (Internet interconnection detection protocol)

Function: used for sending control messages between IP network devices, transmitting error, control, query and other information.

Composition of routing table: next-hop destination network exit interface

The router must know the following information:

1. Destination network segment

2, neighboring routers, and can get information about remote networks from there.

3, discover possible routes to all remote networks

4, choose the best path

5, how to maintain and verify routing information

The router can discover information about the target connection:

A routing entry: multiple options for the next hop of the route to the destination, the path to the destination route and the optimal path to the destination network

What is the next hop: to the next interface or router of the destination network

The data is going to one target:

First: directly connected routing: the cost is relatively small, the router discovers the routing interface independently, and a reasonable IP address should be configured.

Second: static routing: need to be manually configured by the administrator to tell the route how to go, suitable for small and medium-sized networks, manually added, almost will not occupy the router

The third kind: dynamic routing: a route that can be sent and learned by itself, suitable for large networks, can automatically discover routes, and occupies a large amount.

Several dynamic routes:

RIP is based on UDP port number 520

OSPF is based on IP protocol number 89

ECIGRP is based on the IP protocol number 88

BGP is based on TCP port number 179

Routing protocols:

Routing protocols share some information about network status and network accessibility

Routing protocols maintain routing tables and provide the best forwarding path

Be able to communicate with each other

Defines the rules when communicating.

AS: (the two are separate) refers especially to a group of routers managed by the relevant authorities that run the same routing protocol (Chinese can only talk to Chinese, foreigners and foreigners)

IGP: (interior Gateway routing Protocol) specifically refers to RIP OSPF ISIS that can only communicate within AS (Chinese and Chinese say)

EGP: (external Gateway routing Protocol) can also talk in different AS (Chinese can also talk to foreigners) BGP

Algorithm of the protocol:

Distance routing vector protocol: measured by distance, which distance is close to which is used, including RIP BGP

Link-state protocols: also known as shortest path first routing protocols, including OSPF and ISIS

Unicast routing protocols include RIP OSPF BGP IS-IS

Multicast routing protocols include DVMRP,PIM-SM,PIM-DM Anhui Satellite TV

Classful routing protocols do not contain subnet masks to pass RIPV1

Classless routing protocols can include subnet masks for delivery

The main metrics to measure routing protocols:

Correctness of protocol calculation

The algorithm used by the protocol can calculate the optimal route.

The AD value compares the quality of different protocols. The AD value of direct connection is 0. The smaller the AD value, the better.

COST (metric): the distance to the destination address is called cost

Under what circumstances will routing protocol priorities be compared?

If the same route entry is advertised through different routing protocols, the priority needs to be compared, and the smaller the priority, the better.

Under what circumstances do you need to compare COST values?

If the same route is advertised through different neighbors of the same routing protocol, you need to compare the COST value, the smaller the better. If the COST is the same, load sharing is carried out.

Protocol external priority internal priority

Direct (directly connected) 0 0

Static (static) 60 60

OSPF (intra-domain / inter-domain) 10 10

OSPF ASE (external) 150 150

ISIS (Level-1) 15 17

ISIS (Level-2) 15 18

RIP 100 100

BGP (IBGP) 255200

BGP (EBGP) 255 20

Rules for choosing the best path for a router:

Longest mask match

Small is the best for AD.

The measure value should be small first.

First of all, the longer the subnet mask, the better.

Finally, it is passed on by default route.

What is a routing loop:

Routing loop: packets are routed in a loop between two or more routers until the TTL value is reduced to 0 and discarded

Load sharing: there are two or more paths with the same cost or attributes to a destination network.

Features generated by directly connected routes: automatically appear in the routing table

Destination network segment: the network number of the interface IP address

Next hop: interface itself

Summary static: the destination network segment is the network number after the subnet is summarized.

Function: reduce the number of route entries in the routing table and increase the speed at which the router forwards data

How static routes are configured:

Ip route-static 192.168.1.0 255.255.255.0 10.0.12.1\\ destination subnet mask next hop

Ip route-static 0.0.0.0 0.0.0.0 12.1.1.2\\ configure a default route that matches all IP addresses.

To any route, the next hop is 12.1.1.2

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