1 / 127

Routing & Protocols

Routing & Protocols. Paul Traina cisco Engineering. xx. 2. Job Number Goes Here. Today's Talk. Terminology Routing Static Routes Interior Gateway Protocols Exterior Gateway Protocols Building an ISP network. Paul Traina / INET '95 Developing Countries Workshop. 3. Terminology.

arva
Télécharger la présentation

Routing & Protocols

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Routing & Protocols

  2. Paul Trainacisco Engineering xx 2 Job Number Goes Here

  3. Today's Talk • Terminology • Routing • Static Routes • Interior Gateway Protocols • Exterior Gateway Protocols • Building an ISP network Paul Traina / INET '95 Developing Countries Workshop 3

  4. Terminology • network number • prefix • mask (or length) Paul Traina / INET '95 Developing Countries Workshop 4

  5. Static routes hand configured routing • tell the router which way to send packets • based upon final packet destination Paul Traina / INET '95 Developing Countries Workshop 5

  6. Static routes • ip route 10.0.0.0 255.0.0.0 serial 3 • ip route 131.108.0.0 255.255.0.0 171.65.3.4 S3 171.65.3.4 Paul Traina / INET '95 Developing Countries Workshop 6

  7. Terminology Interior Gateway Protocol (IGP) • RIP, IGRP, HELLO, OSPF • Primary goal is optimal connectivity • Strong distance metrics • May not have good administrative controls Paul Traina / INET '95 Developing Countries Workshop 7

  8. Terminology Distance vector protocols • listen to neighboring routers • install routes in table, lowest distance wins • advertise all routes in table • very simple • very stupid Paul Traina / INET '95 Developing Countries Workshop 8

  9. Terminology Distance vector protocols D A G E B A 2 B 2 C 2 D 1 E sup F 1 G 1 H 1 I1 H I F A 1 B 1 C 1 G sup H 1 C Paul Traina / INET '95 Developing Countries Workshop 9

  10. Terminology Link state protocols • information about adjacencies sent to all routers • each router builds a topology database • a "shortest path" algorithm is used to find best route • converge as quickly as databases can be updated Paul Traina / INET '95 Developing Countries Workshop 10

  11. Terminology Link state protocols D A 2 1 G E B 3 H I F C router 3 H, I router 1 A, B, C, G, H router 2 D, E, F, G, I A - 1 - G - 2 - D Paul Traina / INET '95 Developing Countries Workshop 11

  12. Interior Gateway Protocols Routing Information Protocol (RIP) • IP only • distance vector protocol • slow convergence • does not carry mask information • reasonably simple design & configuration • does not scale (maximum 15 hops) • poor metrics (hop-count) Paul Traina / INET '95 Developing Countries Workshop 12

  13. Interior Gateway Protocols Interior Gateway Routing Protocol (IGRP) • IP only • distance vector protocol • slow convergence (like RIP) • does not carry mask information (like RIP) • very simple design & configuration • powerful proprietary metric • load sharing across diverse links Paul Traina / INET '95 Developing Countries Workshop 13

  14. Interior Gateway Protocols The IGRP metric • always get optimal routing • metric vector, not single value • bandwidth • delay • hops • reliability • loading Paul Traina / INET '95 Developing Countries Workshop 14

  15. Interior Gateway Protocols Enhanced IGRP • multi-protocol (IP, IPX, Appletalk) • fast convergence (like OSPF) • very simple design & configuration (like IGRP) • IGRP metric • allows load sharing across diverse links Paul Traina / INET '95 Developing Countries Workshop 15

  16. Interior Gateway Protocols Enhanced IGRP • distance vector based protocol • NOT a Bellman-Ford protocolUses "dual" algorithm • alternative to OSPF & I-ISIS • can be bandwidth intensive on slow links Paul Traina / INET '95 Developing Countries Workshop 16

  17. Interior Gateway Protocols Integrated IS-IS (I-ISIS) • multi-protocol (CLNP, IP, IPX, ...) • link state protocol • fast convergence • design and architecture moderately complex • configuration may be simple Paul Traina / INET '95 Developing Countries Workshop 17

  18. Interior Gateway Protocols Open Shortest Path First (OSPF) • IS - IS = 0 Paul Traina / INET '95 Developing Countries Workshop 18

  19. Interior Gateway Protocols Open Shortest Path First (OSPF) • IP only • link state protocol • fast convergence • design and architecture very complex • configuration can be simple Paul Traina / INET '95 Developing Countries Workshop 19

  20. Interior Gateway Protocols Which to use? • Your interior network is actually VERY simple. • Your IGP should only carry your routes and your direct customers' Paul Traina / INET '95 Developing Countries Workshop 20

  21. Interior Gateway Protcols Problems with "classic" protocols • slow convergence • count to infinity • no mask information • no CIDR • no VLSM • no subnet 0 Paul Traina / INET '95 Developing Countries Workshop 21

  22. Interior Gateway Protocols Slow convergence • advertisement period • entire routing table dumped every n seconds • timeout period • usually 3 times advertisement period • RIP values are normally 30 and 90 seconds! Paul Traina / INET '95 Developing Countries Workshop 22

  23. 1 4 2 3 A B C 1 4 2 3 A B C 1 4 2 3 A B C Interior Gateway Protocols Count to infinty problem 1 (1 hop) 1 (2 hops) 1 (3 hops) route cleared 1 (3 hops) 1 (4 hops) 1 (3 hops) Paul Traina / INET '95 Developing Countries Workshop 23

  24. Interior Gateway Protocols Count to infinity: split-horizon • Don't feed selected route back to source • no feedback on source interface • no feedback to source neighbor Paul Traina / INET '95 Developing Countries Workshop 24

  25. 1 4 2 3 A B C 1 (1 hop) 1 (2 hops) 1 4 2 3 A B C 1 route cleared 4 2 3 A B C route cleared Interior Gateway Protocols Count to infinity: split-horizon 1 (3 hops) 1 (3 hops) route cleared Paul Traina / INET '95 Developing Countries Workshop 25

  26. Interior Gateway Protocols Count to infinity: hold-down • Split horizon not sufficient! • Holddown period • interval during which "less attractive" updates are ignored Paul Traina / INET '95 Developing Countries Workshop 26

  27. Interior Gateway Protocols Count to infinity: hold-down Paul Traina / INET '95 Developing Countries Workshop 27

  28. Interior Gateway Protocols The universal rule • You will always trade bandwidth for speed of convergence Paul Traina / INET '95 Developing Countries Workshop 28

  29. Interior Gateway Protocols OSPF configuration • myth • OSPF is hard to use • reality: • router ospf 1network 192.111.107.0 0.0.0.255 area 0 Paul Traina / INET '95 Developing Countries Workshop 29

  30. Interior Gateway Protocols OSPF operation • every OSPF router sends out 'hello' packets • hello packets used to determine if neighbor is up • hello packets are small easy to process packets • hello packets are sent periodically (usually short interval) Paul Traina / INET '95 Developing Countries Workshop 30

  31. Interior Gateway Protocols OSPF operation • once an adjacency is established, trade information with your neighbor • topology information is packaged in a "link state announcement" • announcements are sent ONCE, and only updated if there's a change • (or every 45mins...) Paul Traina / INET '95 Developing Countries Workshop 31

  32. Interior Gateway Protocols OSPF operation • change occurs • broadcast change • run SPF algorithm • install output into forwarding table Paul Traina / INET '95 Developing Countries Workshop 32

  33. Interior Gateway Protocols making OSPF scale • each link transition causes a broadcast and SPF run • OSPF can group routers to appear as one single router • OSPF areas Paul Traina / INET '95 Developing Countries Workshop 33

  34. Interior Gateway Protocols OSPF areas (before) Paul Traina / INET '95 Developing Countries Workshop 34

  35. Interior Gateway Protocols OSPF areas (after) Paul Traina / INET '95 Developing Countries Workshop 35

  36. Interior Gateway Protocols OSPF areas - partitioning Paul Traina / INET '95 Developing Countries Workshop 36

  37. Interior Gateway Protocols OSPF areas - partition repair Paul Traina / INET '95 Developing Countries Workshop 37

  38. Interior Gateway Protocols OSPF areas • rule of thumb:no more than 150 routers/area • reality:no more than 500 routers/area • backbone "area" is an area • proper use of areas reduce bandwidth & CPU utilization Paul Traina / INET '95 Developing Countries Workshop 38

  39. Interior Gateway Protocols EIGRP operation • design goals were • make it as fast as OSPF & IS-IS • make it trivial to configure • easy migration from IGRP Paul Traina / INET '95 Developing Countries Workshop 39

  40. Interior Gateway Protocols EIGRP operation • router eigrp 1network 192.108.0.0 mask 255.255.0.0 Paul Traina / INET '95 Developing Countries Workshop 40

  41. Interior Gateway Protocols EIGRP operation - caveats • nothing is for free • EIGRP works best on high speed links • EIGRP doesn't scale well in high-meshed frame-relay networks • star networks OK Paul Traina / INET '95 Developing Countries Workshop 41

  42. 150.196 150.196.4.0 .1.0 .3.0 131.108.3.0 .2.0 131.108 Interior Gateway Protocols summarization • classful routing protocols naturally summarize to network numbers at boundaries Paul Traina / INET '95 Developing Countries Workshop 42

  43. Interior Gateway Protocols summarization • classless routing protocols summarize at arbitrary bit boundaries 131.108.0.0/16 131.108.4.32/29 131.108.3.64/27 131.108.4.0/24 Paul Traina / INET '95 Developing Countries Workshop 43

  44. Interior Gateway Protocols route filtering • pseudo-security (bad idea!) • low bandwidth links • eliminate unnecessary information Paul Traina / INET '95 Developing Countries Workshop 44

  45. 131.108/16 150.136/16 44/8 0/0 Interior Gateway Protocols route filtering B C A Paul Traina / INET '95 Developing Countries Workshop 45

  46. Interior Gateway Protocols redistribution • you run OSPF • your neighbor runs RIP OSPF RIP Paul Traina / INET '95 Developing Countries Workshop 46

  47. Interior Gateway Protocols redistribution • run RIP on their interface • router ripnetwork 192.111.107.0 • configure OSPF to redistribute RIP • router ospf 1network 135.111.104.0 0.0.0.255 area 0redistribute rip metric 10 Paul Traina / INET '95 Developing Countries Workshop 47

  48. Interior Gateway Protocols redistribution • bi-directional redistribution MUST be filtered! Paul Traina / INET '95 Developing Countries Workshop 48

  49. Interior Gateway Protocols redistribution • router ripnetwork 192.111.107.0 • router ospf 1network 135.111.104.0 0.0.0.255 area 0redistribute rip metric 10distribute-list 1 out rip • access-list 1 permit 192.111.107.0 0.0.0.255 Paul Traina / INET '95 Developing Countries Workshop 49

  50. Exterior routing xx 50 Job Number Goes Here

More Related