1. Institute of Technology, Sligo Dept of Computing Cisco Semester 4 Chapter 1, version 2.1.3 Review

2. Overview Chapter 1 is a review of the following subjects:  1.2 LAN Switching  1.2 Virtual LANs  1.3 LAN Design  1.4 Routing Protocols  1.5 Access Control Lists  and 1.6 IPX Routing

3. 1.1 LAN Switching 1.1.1 Congestion and Bandwidth As more people utilize a network to share large files, access file servers and connect to the Internet, network congestion occurs. To relieve network congestion, more bandwidth is needed or the available bandwidth must be used more efficiently.

4. 1.1 LAN Switching 1.1.2 Why Segment LANs?  By using segments in a network, less users & devices are sharing the same bandwidth when communicating within the segment.  This process of creating smaller collision and broadcast domains is referred to as segmentation.

5. 1.1 LAN Switching 1.1.3 Segmentation with LAN Switches  A LAN that uses a switched Ethernet topology creates a network that behaves like it only has two nodes - the sending node and the receiving node. They share the 10Mbps bandwidth between them, which means that nearly all the bandwidth is available for the transmission of data.

6. 1.1 LAN Switching 1.1.4 LAN Switching Overview  Switching increases the bandwidth available on a network by creating dedicated network segments and connecting those segments in a virtual network within the switch. This circuit exists only when two nodes need to communicate.

7. 1.1 LAN Switching 1.1.5 How a LAN Switch Learns Addresses  Switches learn device addresses by:  Reading the source address of each packet transmitted  Noting the port where the frame was heard

8. 1.1 LAN Switching 1.1.6 Symmetric Switching  A symmetric switch provides switched connections between ports with the same bandwidth, such as all 10 Mbps or all 100 Mbps ports.

9. 1.1 LAN Switching 1.1.7 Asymmetric Switching  An asymmetric LAN switch provides switched connections between ports of unlike bandwidth, such as a combination of 10 Mbps and 100 Mbps ports.

10. 1.1 LAN Switching 1.1.8 Two Switching Methods  Store and Forward - (entire frame is received)  Cut-through - (destination MAC address is read)  Fast Forward - No error checking  and Fragment Free - Checks for collisions

11. 1.2 Virtual LANs 1.2.1 Introduction to VLANs  VLANs logically segment the physical LAN infrastructure so that broadcast frames are switched only between ports within the same VLAN.

12. 1.2 Virtual LANs 1.2.2 and 1.2.3 Frame Filtering and Frame Tagging  Two ways to implement VLANs are:  Frame filtering, which uses the MAC addresses already within the frame to base switching decisions, and  Frame tagging, in which extra information is added to the frame to identify the VLAN the frame belongs to.

13. 1.2 Virtual LANs 1.2.4 VLANs Establish Broadcast Domains  Members of the same VLAN are members of the same broadcast (but not collision) domain. VLANs break up broadcast domains. Regularly configured bridges and switches segment collision domains.

14. 1.2 Virtual LANs 1.2.5 Port-Centric Virtual LANs  VLAN membership by port maximizes forwarding performance because:  Users are assigned by port  VLANs are easily administered  Security between VLANs is maximized  Packets do not "leak" into other domains  VLANs and VLAN membership are easily controlled across the network

15. 1.2 Virtual LANs 1.2.6 Static VLANs  Static VLANs have the same characteristics as static routes: they are secure, easy to configure, and straightforward to monitor, but they must be setup by an administrator.

16. 1.2 Virtual LANs 1.2.7 Dynamic VLANs Dynamic VLANs are ports on a switch that can automatically determine their VLAN assignments. More administration is required up front to set up the database within the VLAN management software.

17. 1.3 LAN Design 1.3.1 LAN Design Goals  General requirements of network design:  Functionality -- It must work  Scalability -- It must be able to grow  Adaptability -- It must work with future technologies  Manageability -- It must be monitored

18. 1.3 LAN Design 1.3.2 Design Methodology  Three steps describe a simple model that could be used in network design:  Analyze requirements  Develop a LAN structure (topology)  Set up addressing and routing

19. 1.3 LAN Design 1.3.3 What Problem are you Trying to Solve?  The decision to use an internetworking device depends on which problems you are trying to solve for your client.

20. 1.3 LAN Design Types of Problems Include:  Media contention  Excessive broadcasts  Need to transport new payloads  Need for more bandwidth  Overloaded backbone  Network addressing issues

21. 1.3 LAN Design 1.3.4 Developing a LAN Topology  The topology design can be broken into three OSI categories:  Layer 1 - Physical Layer (wire media type)  Layer 2 - Data Link Layer (bridges & switches)  Layer 3 - Network Layer (routers and network addressing)

22. 1.3 LAN Design 1.3.5 Developing Layer 1 LAN Topology  The Physical layer controls the way data is transmitted between nodes. The type of media and topology selected will determine how much and how fast data can travel across the network.

23. 1.3 LAN Design 1.3.6 Extended Star Topology  In larger networks it is not unusual to have more than one wiring closet. By creating multiple wiring closets, multiple catchment areas are created. The secondary wiring closets are referred to as Intermediate Distribution Facilities.

24. 1.3 LAN Design 1.3.7 Developing Layer 2 LAN Topology  The purposes of Layer 2 devices in the network are to provide flow control, error detection and correction, and to reduce congestion in the network.

25. 1.3 LAN Design 1.3.8 Layer 2 Switching  By installing LAN switching at the MDF and IDFs we can start to look at the size of the collision domains and the speed for each horizontal cable and vertical cable run.

26. 1.3 LAN Design 1.3.9 Layer 3 Router for Segmentation  Where there are multiple physical networks, all data traffic from Network 1 destined for Network 2 has to go through the router. The router is the central point in the LAN for traffic destined for the WAN port.

27. 1.3 LAN Design 1.3.10 Server Placement  If servers are to be distributed around the network topology according to function, the networks Layer 2 and 3 must be designed to accommodate this. The Layer 2 LAN switches must have high speed ports allocated for these servers.

28. 1.4 Routing Protocols 1.4.1 Dynamic Routing Operations  The success of dynamic routing depends on two basic router functions:  Maintenance of a routing table  Timely distribution of knowledge in the form of routing updates to other routers

29. 1.4 Routing Protocols 1.4.1 Dynamic Routing Operations  Dynamic routing relies on a routing protocol to share knowledge. A routing protocol describes:  How updates are sent  What is contained in these updates  When to send this information  How to locate recipients of the updates

30. 1.4 Routing Protocols 1.4.2 Representing Distance with Metrics  The metrics most commonly used are:  Bandwidth, Delay, Load Reliability, Hop count, Ticks and Cost  Typically, the smaller the metric number, the better the path.

31. 1.4 Routing Protocols 1.4.3 Classes of Routing Protocols  Most routing protocols are based on one of two routing algorithms: distance vector or link state.  The balanced hybrid approach combines aspects of the link-state and distance vector algorithms.

32. 1.4 Routing Protocols 1.4.4 One Issue: Time to Convergence  The concept of convergence - that is, the time it takes all the routers in a network to share a consistent view of the network - is a key issue for evaluating the performance of routing protocols.

33. 1.4 Routing Protocols 1.4.5 Distance Vector Concept  Distance vector based routing algorithms pass periodic copies of a routing table from router to router. Periodic updates between routers communicate topology changes.

34. 1.4 Routing Protocols 1.4.6 Interior or Exterior Routing Protocols  Exterior routing protocols are used to communicate between autonomous systems. Interior routing protocols are used within a single autonomous system.

35. 1.4 Routing Protocols 1.4.7 Interior IP Routing Protocols  Examples of IP routing protocols are:  RIP- A distance vector routing protocol.  IGRP- Cisco's distance vector routing protocol.  OSPF- A link-state routing protocol.  Enhanced IGRP- A balanced hybrid routing protocol.

36. 1.4 Routing Protocols 1.4.8 IGRP Overview  A primary advantage of IGRP over RIP is that IGRP can use 7 metrics to determine best paths. Of course, the price of all of this extra information is added complexity in configuring and monitoring IGRP.

37. 1.4 Routing Protocols 1.4.9 IGRP Configuration Router(config)# router igrp AS number  selects IGRP as a routing protocol. Router(config-router)# network number  specifies any directly connected networks to be included.

38. 1.5 Access List Overview 1.5.1 What are Access Lists?  Access lists allow an administrator to specify conditions that determine how a router will control traffic flow. Access lists are used to permit or deny traffic through a router interface. The two main types of access lists are standard and extended.

39. 1.5 Access List Overview 1.5.2 How Access Lists Work  Access lists express the set of rules that give added control for packets that enter inbound interfaces, packets that relay through the router, and packets that exit outbound interfaces of the router. Access lists do not act on packets that originate in the router itself.

40. 1.5 Access List Overview 1.5.3 A List of Tests: Deny or Permit  Access list statements operate in sequential, logical order. They evaluate packets from the top down. If a packet header and access list statement match, the packet skips the rest of the statements. If a condition match is true, the packet is permitted or denied.

41. 1.5 Access List Overview 1.5.4 How to Identify Access Lists  Some numbering conventions apply to ACLs:  1-99 are standard IP, 100-199 extended IP, 600-699 Apple Talk, 800-899 standard IPX, 900-999 extended IPX, 1000-1099 IPX SAP.

42. 1.5 Access List Overview 1.5.5 Testing Packets with Access Lists  For TCP/IP packet filters, Cisco IOS access lists check the packet and upper-layer headers.

43. 1.5 Access List Overview 1.5.6 How to Use Wildcard Mask Bits  A wildcard mask bit 0 means "check the corresponding bit value."  A wildcard mask bit 1 means "do not check (ignore) that corresponding bit value."

44. 1.5 Access List Overview 1.5.7 How to Use the Wildcard “Any”  "Any" is an IOS shortcut for 0.0.0.0 255.255.255.255 in an access list statement. It might be used to permit all traffic in one statement, preceding a statement where some specific network traffic is denied.

45. 1.5 Access List Overview 1.5.8 How to Use the Wildcard “Host”  Another IOS shortcut is the "host" command, which replaces 0.0.0.0 as a wildcard mask - meaning all bits must be checked and must match for the access-list statement to be true.

46. 1.5 Access List Overview 1.5.9 Where to Place IP Access Lists  A design rule for placing ACLs is: put the extended ACL as close as possible to the source of traffic denied. In the case of standard ACLs, they can only filter using source address, so they should be put as close to the destination as possible.

47. 1.6 IPX Routing Overview 1.6.1 Cisco Routers in Netware Networks  Cisco's routers offer the following features in Novell network environments:  Access lists and filters for IPX, RIP, SAP, and NetBIOS  Scalable routing protocols, including Enhanced IGRP and NLSP

48. 1.6 IPX Routing Overview  Cisco's routers offer the following features in Novell network environments:  Configurable RIP and SAP updates and packet sizes  Serverless LAN support  Rich diagnostics, management, and troubleshooting features

49. 1.6 IPX Routing Overview 1.6.2 Novell Netware Protocol Suite  Novell IPX has the following characteristics:  It is a connectionless protocol that does not require acknowledgments for each packet (best effort delivery)  It is a Layer 3 protocol that defines internetwork and internode addresses

50. 1.6 IPX Routing Overview 1.6.3 Novell IPX Addressing  Novell IPX addressing uses a two-part address, the network number and the node number. The IPX network number can be up to 8 hexadecimal digits in length. This number is assigned by the network administrator.

51. 1.6 IPX Routing Overview 1.6.4 Cisco Encapsulation Names  When you configure Cisco IOS software for Novell IPX, use the Cisco name for the appropriate encapsulation. If you do not specify an encapsulation type when you configure the router for IPX, the router will use the default encapsulation type on its interfaces.

52. 1.6 IPX Routing Overview 1.6.4 Cisco Encapsulation Names  The default encapsulation types on Cisco router interfaces and their keywords are:  Ethernet-novell-ether  Token Ring-sap  FDDI-snap

53. 1.6 IPX Routing Overview 1.6.5 Novell Uses RIP for Routing  Novell RIP is a distance vector routing protocol. Novell RIP uses two metrics to make routing decisions: ticks (a time measure) and hop count (a count of each router traversed).

54. 1.6 IPX Routing Overview 1.6.6 SAP Service Advertisements  A powerful feature of NetWare networks is the use of SAPs to facilitate client-server transactions.  By default, service advertisements occur at 60- second intervals.

55. 1.6 IPX Routing Overview 1.6.7 GNS Get Nearest Server Protocol  GNS is a broadcast that comes from a client using SAP. The nearest NetWare file server responds with a GNS reply. From that point on, the client can log in to the target server, make a connection, set the packet size, and proceed to use server resources.

56. 1.6 IPX Routing Overview 1.6.8 Novell IPX Configuration Tasks  Four major tasks for configuring IPX exist: enable the IPX routing process, enable load-sharing if appropriate, assign unique network numbers to each router interface, and finally set the IPX encapsulation type if it is different from the default Ethernet_II (arpa).

57. 1.6 IPX Routing Overview  show ipx interface  show ipx route  show ipx servers  show ipx traffic  debug ipx routing activity  debug ipx sap 1.6.9 Verifying IPX Operation Once IPX routing is configured, you can monitor and troubleshoot it using commands such as:

58. 1.6 IPX Routing Overview Summary  This chapter is a review of semester 3, whose focus is on LANs. In the forthcoming chapters, you will shift your focus to WANs. And your case study tasks will shift to WANs as well.