1 / 82

IS-IS Intermediate System-to-Intermediate System

IS-IS Intermediate System-to-Intermediate System. Rick Graziani Cabrillo College graziani@cabrillo.edu Fall 2009. Sources. Sources used in creating this IS-IS presentation: Cisco Online curriculum, CCNP 1 version 3.0 IS-IS Network Design Solutions, Cisco Press Very Good Reference

travis
Download Presentation

IS-IS Intermediate System-to-Intermediate System

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. IS-ISIntermediate System-to-Intermediate System Rick Graziani Cabrillo College graziani@cabrillo.edu Fall 2009

  2. Sources • Sources used in creating this IS-IS presentation: • Cisco Online curriculum, CCNP 1 version 3.0 • IS-IS Network Design Solutions, Cisco Press • Very Good Reference • CCNP Self-Study (BSCI), Cisco Press • Routing TCP/IP Volume I by Jeff Doyle Rick Graziani graziani@cabrillo.edu

  3. IS-IS versus OSPF “IS-IS is exactly the same as OSPF only completely different.”

  4. IS-IS versus OSPF • OSPF – discussed in CCNA and CCNP (Single Area and Multi-Area) • The following slides show terminology differences between IS-IS and OSPF. • Similar to the differences between Spanish and Italian. • Suggestion: Put the following on the board. Rick Graziani graziani@cabrillo.edu

  5. IS-IS versus OSPF - Terminology Rick Graziani graziani@cabrillo.edu

  6. IS-IS versus OSPF - Terminology Rick Graziani graziani@cabrillo.edu

  7. IS-IS versus OSPF – ISs (Routers) Rick Graziani graziani@cabrillo.edu

  8. IS-IS versus OSPF - Timers Rick Graziani graziani@cabrillo.edu

  9. History of IS-IS and OSPF Just like the MacIntosh versus Windows debate

  10. History of IS-IS and OSPF http://www.nanog.org • 1985 • Originally called DECnet Phase V • 1987 • IS-IS (from DEC) selected by ANSI as OSI intradomain protocol (CLNP only) • 1988 • NSFnet deployed, IGP based on early IS-IS draft • OSPF work begins, loosely based on IS-IS mechanisms • IP extensions to IS-IS defined • 1989 • OSPF v.1 RFC published • IS-IS becomes ISO proposed standard • Public bickering ensues--OSPF and IS-IS are blessed as equals by IETF, with OSPF somewhat more equal • Private cooperation improves both protocols • 1990 • Dual-mode IS-IS RFC published Rick Graziani graziani@cabrillo.edu

  11. History of IS-IS and OSPF http://www.nanog.org • 1991 • OSPF v.2 RFC published • Cisco ships OSI-only IS-IS • 1992 • Cisco ships dual IS-IS • Lots of OSPF deployed, but very little IS-IS • 1993 • Novell publishes NLSP (IPX IS-IS knockoff) • 1994 • Large ISPs need an IGP; IS-IS is recommended due to recent rewrite and OSPF field experience (and to lesser extent, NSF CLNP mandate) • 1995 • ISPs begin deployment of IS-IS, Cisco implementation firms up, protocol starts to become popular in niche Rick Graziani graziani@cabrillo.edu

  12. History of IS-IS and OSPF http://www.nanog.org • 1996-1998 • IS-IS niche popularity continues to grow (some ISPs switch to it from OSPF) • IS-IS becomes barrier to entry for router vendors targeting large ISPs • Juniper and other vendors ship IS-IS capable routers • 1999-present • Extensions continue for both protocols Rick Graziani graziani@cabrillo.edu

  13. Who uses IS-IS? • IS-IS is popular amongst telcos and large ISPs (at least in U.S.). • A Tier 1 carrier is a telco or ISP that is at the top of the telecommunications peering and settlements food chain. • Tier 1 operators typically have operations in more than one country • Tier 1 operators own and operate their own physical networks, and either own or part-own their international submarine cable links. • Example of Tier 1 carriers (not necessarily IS-IS users): • AT&T • Global Crossing • Level 3 • NTT/Verio • Qwest • Sprint • Verizon Business (UUNET) Rick Graziani graziani@cabrillo.edu

  14. Introduction to IS-IS Protocol Routers Areas

  15. OSI: Two Network Services, Two Network Protocols • CMNS (Connection Mode Network Service) – Requires establishment of a path between transport layer entites. • CONP (Connection-Oriented Network Protocol) – OSI network layer protocol that carries upper layer data over connection-oriented links. • CLNS (Connectionless Network Service) – Performs datagram support, does not require circuit to be established • CLNP (Connectionless Network Protocol) – OSI network layer protocol that carries upper layer data over connectionless links. (Similar to IP) Rick Graziani graziani@cabrillo.edu

  16. IS-IS Protocol Options • IS-IS (ISO 10589) • Dynamic link state routing protocol used in an ISO CLNS environment. • Integrated IS-IS (RFC 1195) • IS-IS for mixed ISO CLNS and IP environments. • Either: • Purely ISO • Purely IP (CCNP 1) • Both Rick Graziani graziani@cabrillo.edu

  17. OSI Routing Protocols: ES-IS and IS-IS ES-IS • Analogous to Address Resolution Protocol (ARP) in IP • Not technically a routing protocol • Sometimes referred to as Level 0 routing. • ESs (hosts) discover nearest IS (router) by listening to IS Hello (ISH) packets • ISs (routers) know which hosts are on their subnetwork by listening to ES Hello (ESH) packets. • Not applicable for IP networks ISH ESH Rick Graziani graziani@cabrillo.edu

  18. OSI Routing Protocols: ES-IS and IS-IS IS-IS • OSI distinguishes between Level 1, Level 2, and Level 3 routing. • Level 1 Routing • If DA is an ES on another subnetwork in the same area, the IS knows the correct route and forwards packet appropriately. • Level 2 Routing • If DA is an ES on another area, the Level 1 IS sends the packet to the nearest Level 2 IS. (coming) • Level 3 Routing is between separate domains. • Pure CLNS environment IDRP or ISO-IGRP can be used, in IP, BGP is used. (Not applicable to CCNP) Boundary areas in IS-IS exists on a link between routers and not on a router itself as in OSPF. These routers should be entirely in Area 1 and Area 2. Rick Graziani graziani@cabrillo.edu

  19. IS-IS Areas IS-IS Routers: • Level 1 IS (L1 IS, router) • Analogous to OSPF Internal non-backbone router (Totally Stubby) • Responsible for only routing to ESs inside an area. • Level 2 IS (L2 IS, router) • Analogous to OSPF Internal Backbone router • Responsible for routing between areas • Level 1 and Level 2 IS (L1-L2 IS, router) • Analogous to OSPF ABR router • Participate in both L1 intra-area routing and L2 inter-area routing. Rick Graziani graziani@cabrillo.edu

  20. Level 1 Router • Level 1 IS (L1 IS, router) • Analogous to OSPF Internal non-backbone router (Totally Stubby) • Responsible for only routing to ESs inside an area. • Level 1 routers maintain the Level 1 database for the area and exit points to neighboring areas. Rick Graziani graziani@cabrillo.edu

  21. Level 2 Router • Level 2 IS (L2 IS, router) • Analogous to OSPF Internal Backbone router • Responsible for routing between areas • Also referred to as area routers. • Interconnects the Level 1 areas • Store separate database of only inter-area topology Rick Graziani graziani@cabrillo.edu

  22. Level 1 – Level 2Router • Level 1 and Level 2 IS (L1-L2 IS, router) • Analogous to OSPF ABR router • Participate in both L1 intra-area routing and L2 inter-area routing. • Maintain both Level 1 and Level 2 LSDB • Support Level 1 function communicating with other Level 1 routers in their area • Inform other Level 1 routers that they are the exit point (default route) from the area. • Support Level 2 function communicating with the rest of the backbone path. Rick Graziani graziani@cabrillo.edu

  23. IS-IS Backbone • IS-IS does not share the concept of a backbone area 0 with OSPF. • IS-IS backbone a set of distinct areas interconnected by a chain of Level 2 routers, weaving their way through and between the Level 1 Areas. • The IS-IS backbone (path) consists of a contiguous set of Level 1-2 and Level 2 routers. • Where is the backbone (path)? Rick Graziani graziani@cabrillo.edu

  24. OSI Addressing NSAP (Area, System ID, NSEL) SNAP

  25. OSI Addressing • IS-IS uses OSInetwork layer addressing • In IP only networks used to identify the router (IS) • A variety of NSAP formats exist, which we will not go into. • Represented in hexadecimal (up to 40 hex digits) • Cisco format: Area – System ID – NSEL (always 00 on ISs) 49.0001.2222.2222.2222.00 NSAP Rick Graziani graziani@cabrillo.edu

  26. NSAPs • Format of the Cisco NSAP address consists of three parts. • Area address • System ID • NSAP selector byte • Area address is a variable length field • The system ID is the ES or IS identifier in an area, similar to theOSPF router ID. • The system ID has a fixed length of six bytes as engineered in the Cisco IOS. • The NSAP selector byte is a service identifier. • Analogous to that of a port or socket in TCP/IP. Rick Graziani graziani@cabrillo.edu

  27. Do I have to know this, I am only routing IP? • Even in IP only networks, IS-IS uses OSI addresses: • Identify the router (IS) • Build the topology table • Build the SPF tree • LSPs • Hello and other PDUs Rick Graziani graziani@cabrillo.edu

  28. NSAPs – Cisco Format Area • Addresses starting with 49 (AFI=49) are considered private IP address, analogous to RFC 1918. • Routed by IS-IS • Should not be advertised to other CLNS networks (outside this IS-IS domain) • Additional 2 bytes (0001) added for the area ID • All routers in the same are must have the same area address Area – System ID – NSEL 49.0001.2222.2222.2222.00 Rick Graziani graziani@cabrillo.edu

  29. NSAPs – Cisco Format System ID • Cisco fixes the System ID at 6 bytes. • Customary to use one of the following: • MAC address from the router • IP address of loopback interface • 192.168.111.3 -> 192.168.111.003 -> 1921.6811.1003 • Each device (IS and ES) must have a unique System ID within the area. (Recommended to make them unique within the domain.) Area – System ID – NSEL 49.0001.2222.2222.2222.00 Rick Graziani graziani@cabrillo.edu

  30. NSAPs – Cisco Format NSEL (NSAP Selector) • NSEL is a service identifier. • Loosely equivalent to that of a port or socket in TCP/IP. • Not used in routing decisions. NET (Network Entity Title) • When NSEL = 00, it identifies the device itself, the network level address. • The NSAP with a NSEL = 00 is known as a Network Entity Title (NET) • A NET is an NSAP with the NSEL set to (00) Area – System ID – NSEL 49.0001.2222.2222.2222.00 Rick Graziani graziani@cabrillo.edu

  31. NSAP (NETs) Area – System ID – NSEL 49.0001.2222.2222.2222.00 Example 1: NSAP 47.0001.aaaa.bbbb.cccc.00 • Area ID is: • 47.0001 • System ID is: • aaaa.bbbb.cccc • NSAP selector byte is: • 00 Example 2: NSAP 39.0f01.0002.0000.0c00.1111.00 • Area ID is: • 39.0f01.0002 • System ID is: • 0000.0c00.1111 • NSAP selector byte is: • 00 Other Examples Rick Graziani graziani@cabrillo.edu

  32. Configuring IS-IS (so far) Area 49.0001 • ip router isis: IS-IS must be enabled on the interface • Note: IS-IS routing cannot be enabled on an interface until an IP address has been configured on the interface. • IOS: Cisco IOS 12.2(12) with Enterprise Plus (16 MB Flash/48 MB RAM) or Enter Plus IPSec56 (16 MB Flash/64 MB RAM) SanJose1 interface FastEthernet0/0 ip address 172.16.0.1 255.255.255.0 ip router isis isis priority 100 router isis net 49.0001.1111.1111.1111.00 SanJose2 interface FastEthernet0/0 ip address 172.16.0.2 255.255.255.0 ip router isis router isis net 49.0001.2222.2222.2222.00 Area . System ID . NSEL SanJose3 interface FastEthernet0/0 ip address 172.16.0.3 255.255.255.0 ip router isis router isis net 49.0001.3333.3333.3333.00 Rick Graziani graziani@cabrillo.edu

  33. Configuring IS-IS (so far) Area 49.0001 • To display both ES and IS neighbors. • SNPA (Subnetwork Point of Attachment) address is the interface circuit ID. • Ethernet: MAC address of the remote router. • Serial, would show encapsulation, I.e. HDLC • Type: Cisco routers default to L1-L2 type routers. • We will see how to change this in a moment. Rick Graziani graziani@cabrillo.edu

  34. IS-IS Adjacencies Are we half way yet?

  35. Hello Messages • IS-IS uses Hello PDUs to establish adjacencies with other routers (ISs) and ESs. • IS-IS has three types of Hello PDUs: • ESH, sent by ES to an IS • ISH, sent by IS to an ES • IIH, used between two ISs (CCNP) Rick Graziani graziani@cabrillo.edu

  36. Neighbors and Adjacencies • IS-IS discover neighbors and forms adjacencies using IS-IS Hello PDUs. • Transmitted every 10 seconds • Can be changed using the interface command, is hello-interval • Hold time defaults to 3 times the Hello time (30 seconds), before declaring a neighbor dead. • Changed using the interface command is hello-multiplier • Default is 3 Rick Graziani graziani@cabrillo.edu

  37. LAN Representation and Adjacencies • Similar to the DR in OSPF… • DIS (Designated IS) is elected to generate the LSP (Link State Packet, ie. LSA) representing the virtual router connecting all attached routers to a star-shaped topology • LAN uses a virtual node called pseudonode. • Represents the LAN • Sent by the DIS DIS Rick Graziani graziani@cabrillo.edu

  38. LAN Representation and Adjacencies • Election of DIS: • Router with highest priority (Cisco default is 64) • Router with highest MAC address • No “BDR” • No way to make a router ineligible from being DIS (no OSPF priority 0) • New router (IS) can cause a new election, unlike OSPF • Periodically broadcasts CSNPs (OSPF DBD) every 10 seconds DIS Rick Graziani graziani@cabrillo.edu

  39. Configuring IS-IS (so far) DIS Area 49.0001 • isis priority: Sets DIS priority on a LAN interface, default 64 SanJose1 interface FastEthernet0/0 ip address 172.16.0.1 255.255.255.0 ip router isis isis priority 100 router isis net 49.0001.1111.1111.1111.00 SanJose2 interface FastEthernet0/0 ip address 172.16.0.2 255.255.255.0 ip router isis router isis net 49.0001.2222.2222.2222.00 Area . System ID . NSEL SanJose3 interface FastEthernet0/0 ip address 172.16.0.3 255.255.255.0 ip router isis router isis net 49.0001.3333.3333.3333.00 Rick Graziani graziani@cabrillo.edu

  40. Adjacencies • L1 routers form L1 adjacencies with L1 and L1-L2 routers in their area. • L2 routers form L2 adjacencies with L2 and L1-L2 routers in their area or another area. • L1 router does not form an adjacency with an L2 router LAN Adjacencies Rick Graziani graziani@cabrillo.edu

  41. Adjacencies • What are the adjacencies? L1? L2? L1L2? None? • The adjacencies also determine what type of routes the IS (router) will have in its routing table. • L1 – Intra-area routes (routes only within that area) • L2 – Inter-area routes (routes from other areas) • Or both Rick Graziani graziani@cabrillo.edu

  42. Adjacencies • For an adjacency to be formed and maintained, routers must agree on: • If they are both Level 1, them must be in the same area • The System ID must be unique to each router. • The Hello timers do not have to match. Rick Graziani graziani@cabrillo.edu

  43. Metric and Calculate the Shortest Path • Four types of metrics: • Default – Cisco only supports this metric. • Delay • Expense • Error • Each metric expressed as an integer between 0 and 63. Rick Graziani graziani@cabrillo.edu

  44. Metric • Cisco assigns a default metric of 10 to every interface regardless of interface type. • Total cost of any route = sum of metrics of the outgoing interfaces. • By default, IS-IS metric becomes a simple measure of hop count. • Interface command: isis metric changes the default value. Rick Graziani graziani@cabrillo.edu

  45. Multi-Area IS-IS Example

  46. Note: ip router isis command must be added not only to transit interfaces but also to interfaces connected to stub networks whose IP addresses should be advertised by IS-IS. Levels L1L2 • is-type {level-1 | level-1-2 | level-2-only} SanJose1 interface FastEthernet0/1 ip address 192.168.10.1 255.255.255.252 ip router isis interface FastEthernet0/0 ip address 172.16.0.1 255.255.255.0 ip router isis interface Serial0/0 ip address 10.0.0.2 255.255.255.252 ip router isis router isis net 49.0001.1111.1111.1111.00 is-type level-1-2 SanJose2 interface FastEthernet0/0 ip address 172.16.0.2 255.255.255.0 ip router isis interface FastEthernet0/1 ip address 192.168.20.1 255.255.255.0 ip router isis router isis net 49.0001.2222.2222.2222.00 is-type level-1 L1 L2 Phoenix interface Serial0/0 ip address 10.0.0.1 255.255.255.252 ip router isis interface FastEthernet0/1 ip address 192.168.30.1 255.255.255.0 ip router isis router isis net 49.0002.3333.3333.3333.00 is-type level-2-only Rick Graziani graziani@cabrillo.edu

  47. show clns neigh L1L2 SanJose1#show clns neighbors System Id Interface SNPA State Holdtime Type Protocol SanJose2 Fa0/0 0003.6be9.d480 Up 26 L1 IS-IS Phoenix Se0/0 *HDLC* Up 28 L2 IS-IS SanJose2#show clns neighbors System Id Interface SNPA State Holdtime Type Protocol SanJose1 Fa0/0 0002.b9ee.5ee0 Up 4 L1 IS-IS Phoenix#show clns neighbors System Id Interface SNPA State Holdtime Type Protocol SanJose1 Se0/0 *HDLC* Up 27 L2 IS-IS • System ID – Cisco IOS uses the hostname. • SNPA is the MAC of the remote router or HDLC on the serial link. • The Type is the is-type of the remote router. L1 L2 Rick Graziani graziani@cabrillo.edu

  48. show isis data L1L2 SanJose1#show isis database IS-IS Level-1 Link State Database: LSPID LSP Seq Num LSP Checksum LSP Holdtime ATT/P/OL SanJose1.00-00 * 0x00000005 0xDE15 916 1/0/0 SanJose1.01-00 * 0x00000003 0xBBFE 1165 0/0/0 SanJose2.00-00 0x00000006 0xBDFB 470 0/0/0 IS-IS Level-2 Link State Database: LSPID LSP Seq Num LSP Checksum LSP Holdtime ATT/P/OL SanJose1.00-00 * 0x0000001B 0xAB48 914 0/0/0 SanJose1.01-00 * 0x0000001B 0x5526 480 0/0/0 Phoenix.00-00 0x0000001E 0xA3D3 912 0/0/0 Phoenix.01-00 0x00000002 0x54A6 826 0/0/0 • SanJose1 has a L1 LSDB and a L2 LSDB. L1 L2 Rick Graziani graziani@cabrillo.edu

  49. show isis data L1L2 SanJose2#show isis database IS-IS Level-1 Link State Database: LSPID LSP Seq Num LSP Checksum LSP Holdtime ATT/P/OL SanJose1.00-00 0x00000005 0xDE15 907 1/0/0 SanJose1.01-00 0x00000003 0xBBFE 1155 0/0/0 SanJose2.00-00 * 0x00000006 0xBDFB 464 0/0/0 Phoenix#show isis database IS-IS Level-2 Link State Database: LSPID LSP Seq Num LSP Checksum LSP Holdtime ATT/P/OL SanJose1.00-00 0x0000001B 0xAB48 893 0/0/0 SanJose1.01-00 0x0000001B 0x5526 459 0/0/0 SanJose2.00-00 0x00000024 0x2FD3 0 (932) 0/0/0 Phoenix.00-00 * 0x0000001E 0xA3D3 895 0/0/0 Phoenix.01-00 * 0x00000002 0x54A6 808 0/0/0 • SanJose2 only has a L1 LSDB. • Phoenix only has a L2 LSDB. L1 L2 Rick Graziani graziani@cabrillo.edu

  50. show ip route L1L2 SanJose1#show ip route i L2 192.168.30.0/24 [115/20] via 10.0.0.1, Serial0/0 C 192.168.10.0/24 is directly connected, FastEthernet0/1 172.16.0.0/24 is subnetted, 1 subnets C 172.16.0.0 is directly connected, FastEthernet0/0 i L1 192.168.20.0/24 [115/20] via 172.16.0.2, FastEthernet0/0 10.0.0.0/30 is subnetted, 1 subnets C 10.0.0.0 is directly connected, Serial0/0 • Because SanJose1 is an L1L2 router, it contains both: • L1 routes for Area 49.0001 and • L2 routes for the other area 49.0002. L1 L2 Rick Graziani graziani@cabrillo.edu

More Related