Basic static routing and dynamic routing Rifki Indra, S.Kom., M.Eng. http://learning.upnyk.ac.id

Basic Routing Concept

Definisi Static Routing Static routing adalah salah satu teknik mentransmisikan/mengirimkan paket data dari network satu ke network lain melalui rute yang sudah ditetapkan. (oleh admin)

Basic Router concept Pastikan paket data yang akan dikirim dengan tujuan yang satu network atau beda network…?

Define a route and its three key parts

Explain how routes are manually configured to build routing table

Router#ip route 0.0.0.0 0.0.0.0 <exit interface> Command routing static Router#ip route <net id tujuan> <netmask> <ip next hop> Router#ip route 0.0.0.0 0.0.0.0 <exit interface>

Advantages and Disadvantages Advantages of static routing It can backup multiple interfaces/networks on a router Easy to configure No extra resources are needed More secure Disadvantages of static routing Network changes require manual reconfiguration Does not scale well in large topologies

Studi kasus : Bagaimana agar paket dari PC1 sampai ke PC3?

Pahami dahulu tabel berikut Device Port IP Gateway Router 1 S0/0/0 - DCE 192.168.2.1 N/A Fa0/0 172.16.1.1 Router 2 S0/0/0 192.168.2.2 S0/0/1 - DCE 192.168.1.1 172.16.2.1 Router 3 192.168.1.2 172.16.3.1 PC1 - 172.16.1.10 PC2 172.16.2.10 PC3 172.16.3.10

Routing Dynamic Routing dynamis adalah teknik mengirimkan paket data antar network melalui rute yang dipilih oleh router dengan mempertimbangkan best path.

Dynamic Routing Protocols Function(s) of Dynamic Routing Protocols: Dynamically share information between routers. Automatically update routing table when topology changes. Determine best path to a destination.

The purpose of a dynamic routing protocol is to: Discover remote networks Maintaining up-to-date routing information Choosing the best path to destination networks Ability to find a new best path if the current path is no longer available

Components of a routing protocol Algorithm In the case of a routing protocol algorithms are used for facilitating routing information and best path determination Routing protocol messages These are messages for discovering neighbors and exchange of routing information

Classifying Routing Protocols Dynamic routing protocols are grouped according to characteristics. Examples include: RIP IGRP EIGRP OSPF IS-IS BGP BGP ospf IS IS RIP 1 IGRP RIP 2 EIGRP

Routing RIP Routing Information Protocol (RIP) adalah sebuah protokol routing dinamis yang digunakan dalam jaringan LAN (Local Area Network) dan WAN (Wide Area Network). Oleh karena itu protokol ini diklasifikasikan sebagai Interior Gateway Protocol (IGP). Protokol ini menggunakan algoritma Distance-Vector Routing. Pertama kali didefinisikan dalam RFC 1058 (1988). Protokol ini telah dikembangkan beberapa kali, sehingga terciptalah RIP Versi 2 (RFC 2453). Kedua versi ini masih digunakan sampai sekarang, meskipun begitu secara teknis mereka telah dianggap usang oleh teknik-teknik yang lebih maju, seperti Open Shortest Path First (OSPF) dan protokol OSI IS-IS.

Cara Kerja RIP Host mendengar pada alamat broadcast jika ada update routing dari gateway. Host akan memeriksa terlebih dahulu routing table lokal jika menerima update routing . Jika rute belum ada, informasi segera dimasukkan ke routing table . Jika rute sudah ada, metric yang terkecil akan diambil sebagai acuan. Rute melalui suatu gateway akan dihapus jika tidak ada update dari gateway tersebut dalam waktu tertentu. Khusus untuk gateway, RIP akan mengirimkan update routing pada alamat broadcast di setiap network yang terhubung

Distance vector routing protocol Hop count sebagi metric untuk memilih rute, Maximum hop count 15, hop ke 16 dianggap unreachable Secara default routing update 30 detik sekali RIPv1 (classfull routing protocol) tidak mengirimkan subnet mask pada update RIPv2 (classless routing protocol) mengirimkan subnet mask pada update

RIP v1 dan RIP v2 RIP v1 tidak mendukung vlsm RIP v1 tidak mengirimkan update routing dan netmask RIP v1 perbaikan broadcat RIP v2 mendukung vlsm RIP v2 mengirimkan update routing serta netmask RIP v2 perbaikan multicast

Syntax Router (config-router)#passive interface fastethernet directly connected

Studi kasus : RIP v1

RIP v2 Syntax : Untuk masing-masing router berlaku : Router(config)#router rip Router(config-router)#version 2 Router(config-router)#network directly connect Router(config-router)#no auto summary

Studi kasus : RIP v2

Distance Vector Routing Protocols Factors used to determine whether to use RIP or EIGRP include -Network size -Compatibility between models of routers -Administrative knowledge

Distance Vector Routing Protocols

Classifying Routing Protocols

Classifying Routing Protocols Classful routing protocols Do NOT send subnet mask in routing updates Classless routing protocols Do send subnet mask in routing updates.

Classifying Routing Protocols Convergence is defined as when all routers’ routing tables are at a state of consistency

Routing Protocols Metrics A value used by a routing protocol to determine which routes are better than others.

Routing Protocols Metrics Metrics used in IP routing protocols Bandwidth Cost Delay Hop count Load Reliability

Routing Protocols Metrics The Metric Field in the Routing Table Metric used for each routing protocol -RIP - hop count -IGRP & EIGRP - Bandwidth (used by default), Delay (used by default), Load, Reliability -IS-IS & OSPF – Cost, Bandwidth (Cisco’s implementation)

Routing Protocols Metrics Load balancing This is the ability of a router to distribute packets among multiple same cost paths

Administrative Distance of a Route Purpose of a metric It’s a calculated value used to determine the best path to a destination Purpose of Administrative Distance It’s a numeric value that specifies the preference of a particular route

Administrative Distance of a Route Identifying the Administrative Distance (AD) in a routing table It is the first number in the brackets in the routing table

Administrative Distance of a Route Dynamic Routing Protocols

Routing Loops Routing loops are A condition in which a packet is continuously transmitted within a series of routers without ever reaching its destination.

Routing Loops Routing loops may be caused by: -Incorrectly configured static routes -Incorrectly configured route redistribution -Slow convergence -Incorrectly configured discard routes Routing loops can create the following issues -Excess use of bandwidth -CPU resources may be strained -Network convergence is degraded -Routing updates may be lost or not processed in a timely manner

Routing Loop Prevention Setting a maximum Distance Vector routing protocols set a specified metric value to indicate infinity Once a router “counts to infinity” it marks the route as unreachable

Routing Loop Prevention Preventing loops with holddown timers Holddown timers allow a router to not accept any changes to a route for a specified period of time. Point of using holddown timers Allows routing updates to propagate through network with the most current information.

Routing Loop Prevention The Split Horizon Rule is used to prevent routing loops Split Horizon rule: A router should not advertise a network through the interface from which the update came.

Routing Loop Prevention Split horizon with poison reverse The rule states that once a router learns of an unreachable route through an interface, advertise it as unreachable back through the same interface

Routing Loop Prevention IP & TTL Purpose of the TTL field The TTL field is found in an IP header and is used to prevent packets from endlessly traveling on a network How the TTL field works TTL field contains a numeric value. The numeric value is decreased by one by every router on the route to the destination. If numeric value reaches 0 then Packet is discarded.

Link-State Routing Dikjstra’s algorithm also known as the shortest path first (SPF) algorithm

Link-State Routing The shortest path to a destination is not necessarily the path with the least number of hops

Link-State Routing Link-State Routing Process How routers using Link State Routing Protocols reach convergence -Each routers learns about its own directly connected networks -Link state routers exchange hello packet to “meet” other directly connected link state routers. -Each router builds its own Link State Packet (LSP) which includes information about neighbors such as neighbor ID, link type, & bandwidth. -After the LSP is created the router floods it to all neighbors who then store the information and then forward it until all routers have the same information. -Once all the routers have received all the LSPs, the routers then construct a topological map of the network which is used to determine the best routes to a destination

Link-State Routing Sending Hello Packets to Neighbors Connected interfaces that are using the same link state routing protocols will exchange hello packets. Once routers learn it has neighbors they form an adjacency -2 adjacent neighbors will exchange hello packets -These packets will serve as a keep alive function

Link-State Routing Constructing a link state data base Routers use a database to construct a topology map of the network

Link-State Routing

Link-State Routing Once the SPF algorithm has determined the shortest path routes, these routes are placed in the routing table.