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S4 C1

S4 C1. REVIEW. Review Topics. Switching, VLANs, LAN Design, Routing Protocols (especially IGRP), ACLs, and IPX Why use LAN switching and VLANs Must gather and assess user requirements Select best routing protocol

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S4 C1

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  1. S4 C1 REVIEW

  2. Review Topics • Switching, VLANs, LAN Design, Routing Protocols (especially IGRP), ACLs, and IPX • Why use LAN switching and VLANs • Must gather and assess user requirements • Select best routing protocol • Device a method to control data packet flow based on access control lists (ACLs) • Design for multiple protocols – IPX and IP

  3. Network Demands • Increase in large graphic files, images, and full-motion video – place strain on 10 Mbps • Network utilization sharing large files, accessing database servers, etc. results in network congestion which is evidenced by slower response times, longer file transfers, and decreased productivity • SOLUTION – MORE BANDWIDTH

  4. Why Segmentation? • Decrease network congestion • Data passed between segments is transmitted on backbone which is its own collision domain

  5. LAN Switch Segmentation • Switch eliminates impact of collisions through microsegmentation • Switch results in low latency and high frame-forwarding rate • LAN segmentation works with 802.3 (CSMA/CD) compliant interfaces and cabling

  6. How a LAN Switch Operates • Enables dedicated access, eliminates collisions, increases capacity, and supports multiple conversations • Acts as multiport bridge creating smaller collisions domains; transparent to upper layers and uses layer 2 MAC address • Forwards frames based on forwarding table and MAC addresses

  7. How the LAN Switch Learns Addresses • Examines source address of frames coming in to switch • Sends frame out all ports expect the port the frame entered when the address is broadcast, multicast, or unknown • Forwards frame when the destination is on a different segment (interface) • Filters when the destination is on the same interface

  8. Symmetric/Asymmetric • Symmetric • Provides switching between like bandwidths • Multiple simultaneous conversations increase network throughput • Asymmetric • Provides switching between unlike bandwidths • Requires the switch to use memory buffering

  9. Switching Types • Cut Through • Lowest latency; only reads 6 bytes • No error checking – sends as soon as outgoing interface is determined • Fragment Free • Low latency • Checks for collisions (filters most errors) – reads 64 bytes • Store and Forward • Highest latency • All errors filtered • Does CRC before looking up destination tables and forwarding the frame

  10. VLANS • Group of ports or users in same broadcast domain • Based on port ID, MAC address, protocol, or application • Created with switches and network management software • Frame tagged with VLAN ID

  11. LVAN & Broadcast Transmission • Logical network independent of members’ physical locations • Administratively defined broadcast domain • Users reassigned to different VLAN using software • Broadcast Transmission • Single data packet sent into network and copies and set to every network node

  12. Frame Filtering • A filtering table is developed for each switch • Switches share address table information • Table entries are compared to frames • Switch takes appropriate action

  13. Frame Tagging • Developed for multi-VLAN interswitched communication • Places unique identifier in header of each frame as it travels across vertical cabling • Identifier removed before frame exits switch on non-backbone links • Layer 2 Protocol • Requires little processing and administrative overhead

  14. VLAN Broadcast Demands • VLANS and routers restrict broadcasts to domain of origin • Adjacent ports do not receive broadcast traffic generated from other VLANs • Control the size of broadcast domain by limiting the size of the VLAN

  15. Port-Centric VLANS • All nodes attached to the same router port must be in the same broadcast domain • 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 network

  16. Static VLANs • Statically assigned ports (port-centric is one type of static VLAN) • Secure – only ports identified with VLAN receive broadcast • Easy to configure and monitor • Easy to reassign port to another VLAN

  17. Dynamic VLANs • Assigned using centralized VLAN management application • Based on MAC address, logical address, or protocol type • Less administration in wiring closet • Notification when unrecognized user is added to network • More administration required up front to set up database within VLAN management software and to maintain accurate database of users

  18. LAN Design Goals • Functionality • Scalability • Adaptability • Manageability

  19. Design Methodology • Know Client – Determine Client goals • Analyze requirements • Develop LAN structure (physical and logical topology) • Set up addressing and routing

  20. Problems LAN Design Solves • Media contention • Excessive broadcasts • Need to transport new payloads • Need for more bandwidth • Overloaded backbone • Network layer addressing issues

  21. Topology Issues • Where are routers placed? • Where are switches placed? • What type of network media is used? • Do you use hubs, repeaters? • Design Goals • MDF (concentration point) with IDFs • LAN switching and microsegmentation

  22. Design Goals Continued • Create LAN segments that will filter flow of data packets • Isolate ARP broadcasts • Isolate collisions between segments • Filter Layer 4 services between segments • Router is the central point in the LAN for traffic destined for the WAN port.

  23. More Design Goals • Within the MDF and IDFs, the Layer 2 LAN switches must have high speed (100Mbps) ports allocated for servers.

  24. Routing Metrics • A number used to represent distance and costs • Bandwidth, delay, load reliability, hops, ticks, Costs • Information used to select best path for routing

  25. Routing Protocols • Distance vector – adds metrics • Link State (SPF) re-creates the exact topology of entire internetwork • Balanced hybrid – combines aspects of link-state and distance vector

  26. Distance VectorBellman-Ford • Pass periodic copies of routing table from router to router • Routers do not know exact topology of network

  27. Exterior / Interior Routing Protocols • Exterior – communicate between autonomous systems • BGP and EGP • Interior – communicate within autonomous system • IGRP, EIGRP, OSPF, RIP

  28. IGRP • Cisco Proprietary • Uses bandwidth, delay, load, reliability, and MTU (Maximum transmission Unit) • Versatile, complex topologies, flexible for segments with different bandwidths, scalable • Router igrp autonomous-system • Network network-number

  29. Access Lists • Standard • Simpler address specifications • Generally permits or denies entire protocol suite • Extended • More complex address specifications • Generally permits or denies specific protocols • Permits or denies with more granularity M

  30. How Access Lists Work • For logical completeness, an access list must have conditions that test true for all packets using the access list. A final implied statement covers all packets for which conditions did not test true. This final test condition matches all other packets. It results in a deny. Instead of proceeding in or out an interface, all these remaining packets are dropped.

  31. Access List Numbers • IP standard 1-99 • IP Extended 100-199 * Named (Cisco IOS 11.2 and higher) • IPX standard 800-899 • IPX extended 900-999 • SAP Filters 1000-1099 • AppleTalk 600-699

  32. Access Lists Check For • Source IP address • Destination IP address • Specific protocols • Upper-level TCP or UDP port

  33. Wildcard Masks • 0 bit means check the corresponding bit value • 1 bit means do not check the corresponding bit value • ANY can replace 0.0.0.0 255.255.255.255 • 0.0.0.0 means any network • 255.255.255.255 means do not check any • Host ip address means check all bits

  34. Placing IP Access Lists • Place standard access lists close to destination • Place extended access lists close to the source

  35. Cisco/Novell Compatibility • Uses Access lists and filters for IPX, RIP, SAP, and NetBIOS • Scalable routing protocols, including Enhanced IGRP and NLSP • Configurable RIP and SAP updates and packet sizes • Server-less LAN support • Rich diagnostics, management, and troubleshooting features

  36. Novell • Network protocol stack supports all common media access protocols. Data link and physical layers accessed through ODI (Open Data Link Interface) • RIP routing information • SAP advertise network services • NCP provides client-to-server connections and applications • SPX connection oriented services

  37. Novell Addressing • 80 bits • 32 network • 48 host – MAC address • No subnets • No need for ARP

  38. Cisco Encapsulation • Ethernet • Ethernet_802.3 novell-ethernet • Ethernet_802.2 sap • Ethernet_II arpa • Ethernet_Snap snap • Token Ring • Token-ring sap • Token-ring_snap snap • FDDI FDDI_SNAP snap • FDDI=802.2 sap • FDDI_Raw novell-fddi

  39. Novell Routing • Uses ticks and top counts • Broadcasts every 60 seconds • Uses simple split horizon • Does not advertise routes that were learned from the same port • Load shares based on IPX maximum-paths

  40. SAPs • SAP packets advertise all NetWare services • Can add excessive broadcast traffic • Routers listen to SAPS and build tables for known services and broadcast table every 60 seconds • Router responds to queries by providing network address – client contacts device directly

  41. GNS • Broadcast from client needing a server • Server and router get SAP packet • Servers provide GNS response

  42. IPX Routing Configuration • Global • IPX Routing • Load Sharing • Interface Configuration • Network numbers • Encapsulation Type

  43. Show Commands and Troubleshooting • Show ipx interface • Show ipx route • Show ipx servers • Show ipx traffic • Debug ipx routing activity • Debug ipx sap

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