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Konsep Routing dan Protokol

Konsep Routing dan Protokol. Pengenalan. Latarbelakang Open Shortest Path First (OSPF). Began in 1987 1989 OSPFv1 released in RFC 1131 This version was experimental & never deployed 1991 OSPFv2 released in RFC 1247 1998 OSPFv2 updated in RFC 2328 1999 OSPFv3 published in RFC 2740.

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Konsep Routing dan Protokol

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  1. Konsep Routing dan Protokol

  2. Pengenalan

  3. Latarbelakang Open Shortest Path First (OSPF) • Began in 1987 • 1989 OSPFv1 released in RFC 1131 This version was experimental & never deployed • 1991 OSPFv2 released in RFC 1247 • 1998 OSPFv2 updated in RFC 2328 • 1999 OSPFv3 published in RFC 2740

  4. Pengkapsulan Mesej OSPF (Message Encapsulation) • Data link frame header Contains - Source MAC address Destination MAC address • IP packet header Contains - Source IP address, Destination IP address, & Protocol field set to 89 • OSPF packet header Contains - Router ID and area ID, & Type code for OSPF packet type • OSPF packet type - One of 5 types

  5. Jenis-jenis Paket OSPF

  6. Tujuan Packet Hello OSPF • mencari rakan/jiran (neighbors) OSPF & menubuhkan bersebelahan • mengemukakan garis panduan yang perlu diterima oleh router untuk menjadi neighbors • Digunakan sebagai rangkaian pelbagai akses (multi-access networks) untuk memilih router (designated router) dan router sandaran (backup designated router) yang ditetapkan/direkabentuk DRdesignated router BDR backup designated router

  7. OSPF • Paket Hello (Hello Packets) -kandungan paket jenis Hello -ID router untuk menghantar router • OSPF Hello Selang (OSPF Hello Intervals) • biasanya multicast (224.0.0.5) • Dihantar setiap 30 saat untuk setiap segmen NBMA • OSPF Selang Mati (OSPF Dead Intervals) • adalah masa yang mesti diketahui umum sebelum neighbor dianggap down • Masa lalai (Default time) adalah 4 kali “hello” interval

  8. OSPF • Protokolpaket Hello mengandungimaklumat yang digunakandalampemilihan -Designated Router (DR) • Router yang bertanggungjawabuntukmengemaskinikansemua router OSPF lain -Backup Designated Router (BDR) • Routerinimengambilalihtanggungjawab DR jika DR gagal

  9. OSPF Link-state Updates • Tujuan Link State Update (LSU) - Digunakan untuk membuat sebaran Link State • Tujuan Link State Advertisement (LSA) - Mengandungi maklumat tentang neighbors & path costs

  10. Algorithma OSPF • Router OSPF membina & mengawal pangkalan data link-state yang mengandungi LSA yang diterima daripada router lain • Maklumat yang terdapat di dalam pangkalan data digunakan apabila melaksanakan algoritma SPF dijkstra • algorithma SPF digunakan untuk membina SPF tree • SPF tree digunakan untuk mengisi jadual routing

  11. Administrative Distance

  12. Pengesahan (Authentication) OSPF • Tujuannya adalah untuk menyulitkan & mengesahkan maklumat routing • Ia adalah konfigurasi antaramuka spesifik (interface specific) • Routers hanya akan terima maklumat routing dari router lain yang dikonfigurasi dengan katakunci (password) ataupengesahan maklumat yang sama sahaja

  13. Topologi • Discontiguous IP addressing scheme • Since OSPF is a classless routing protocol the subnet mask is configured in each router

  14. The router OSPF command • To enable OSPF on a router use the following command R1(config)#router ospf process-id Where the Process id • Is a locally significant number between 1 and 65535

  15. OSPF network command Requires: network address wildcard – NOT a subnet mask area-id - refers to the OSPF area. The OSPF area is a group of routers sharing link state information Router(config-router)#networknetwork-address wildcard-ask areaarea-id

  16. Asas Konfigurasi OSPF • Router ID • IP address digunakan untuk kenalpasti router • Tiga kriteria untuk memperolehi ID router: • Router-id IP address • Loopback IP address • Highest IP address on any active interface

  17. Commands used to verify current router ID Show ip protocols Show ip ospf Show ip ospf interface

  18. Commands used to verify current router ID

  19. Arahan yang digunakan untuk mengesahkan ID router semasa • Show ip protocol • show ipospf • Show ipospf interface

  20. Commands used to verify current router ID

  21. OSPF Router ID • Router ID & Loopback addresses -Highest loopback address will be used as router ID if router-id command isn’t used -Advantage of using loopback address the loopback interface cannot fail  OSPF stability • The OSPF router-id command • Introduced in IOS 12.0 • Command syntax • Router(config)#router ospfprocess-id • Router(config-router)#router-idip-address • Modifying the Router ID • Use the commandRouter#clear ipospf process

  22. Verifying OSPF • Use the show ip ospf command to verify & trouble shoot OSPF networks Command will display the following: • Neighbor adjacency -No adjacency indicated if: • Neighboring router’s Router ID is not displayed • A state of full is not displayed -Consequence of no adjacency: • No link state information exchanged • Inaccurate SPF trees & routing tables result

  23. Verifying OSPF - Additional Commands

  24. Examining the routing table • Use the show ip route command to display the routing table NOTE - OSPF does not automatically summarize at major network boundaries

  25. OSPF Metric • OSPF uses cost as the metric for determining the best route -The best route will have the lowest cost -Costis based on bandwidth of an interface • Cost is calculated using the formula - 108 / bandwidth -Reference bandwidth • defaults to 100Mbps • can be modified using the auto-cost reference-bandwidth command

  26. OSPF Metric • Biasanya kelajuan rangkaian sebenar adalah berbeza jika dibandingkan dengan default bandwidth • Ini menjadikan ia amat penting bahawa nilai bandwidth mencerminkan kelajuan sebenar pautan • Alasannya: Jadual routing mempunyai maklumat laluan terbaik • Arahan show interfaceakan memaparkan antaramuka bandwidth -kebanyakan serial link default kepada 1.544Mbps = T1

  27. Modifying the Cost of a link • Kedua-dua belah pautan bersiri sepatutnya dikonfigurasi dengan bandwidth yang sama • Dua arahan yang digunakan untuk mengubahsuai bandwidth: • Bandwidth command • Example: R1(config-if)#bandwidth bandwidth-kbps • ip ospf cost command – allows you to directly specify interface cost -Example: R1(config)#interface serial 0/0/0 R1(config-if)#ip ospf cost 1562

  28. Perubahan (Changing) Bandwidth

  29. Changing Cost

  30. Modifying the Cost of the link • Perbezaan di antara arahan bandwidth & arahan kos IP OSPF • Bandwidth • Link cost is calculated • IP OSPF cost • Sets cost to a specific value

  31. Challenges in Multi-access Networks OSPF defines five network types: • Point-to-point • Broadcast Multi-access • Non-broadcast Multi-access (NBMA) • Point-to-multipoint • Virtual links

  32. Two challenges presented by multi-access networks • Multiple adjacencies • Extensive LSA flooding

  33. OSPF in Multiaccess Networks • Extensive flooding of LSAs For every LSA sent out there must be an acknowledgement of receipt sent back to transmitting router. consequence: lots of bandwidth consumed and chaotic traffic

  34. OSPF in Multiaccess Networks • Solution to LSA flooding issue is the use of • Designated router (DR) • Backup designated router (BDR) • DR & BDR selection • Routers are elected to send & receive LSA • Sending & Receiving LSA • DRothers send LSAs via multicastaddress224.0.0.6to DR & BDR • DR forward LSA via multicast address 224.0.0.5to all other routers

  35. OSPF in Multiaccess Networks

  36. DR/BDR Election Process • DR/BDR elections DO NOToccur in point to point networks

  37. OSPF in Multiaccess Networks • DR/BDR elections will take place on multiaccess networksas shown below

  38. OSPF in Multi-access Networks • Kriteria untuk membuat pilihan samada DR/BDR • DR: Router with the highest OSPF interface priority. • BDR: Router with the second highest OSPF interface priority. If OSPF interface priorities are equal, then the Highest router ID is used to break the tie.

  39. OSPF in Multi-access Networks

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