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Part 1 - Chapter 2 (Switch operation)

Luis Domínguez CCNP SWITCH 300-115 300-115 Inglés 42 fichas

Fichas del conjunto (42)

  1. 1CSMA/CDDecides when a device can transmit data on a shared LAN
  2. 2Shared media networkMany host that share network and bandwidth
  3. 3Collision domainCollision occurs when two or more host transmit at the same time and forces to use half-duplex mode. Collisions are heard by all in the network included error frames (shared network).
  4. 4Unknown unicast floodingFrame that is forwarding in best effort fashion when destination MAC address is not found in the MAC table
  5. 5FloodingIs when a frame has a multicast destination address (ffff.ffff.ffff) and is flooded for all ports on the Vlan.
  6. 6MLSMulti Layer Switching are switches capable of forwards frames on Layer 3 and 4
  7. 7Type of multilayer switching (MLS)1.- Route caching (1st-generation) MLS
    2.- Topology based (2nd-generation) MLS
  8. 8Cisco switching methods1. Process switching
    2. Fast switching (route caching)
    3. Cisco Express Forwarding (topology-based switching)
  9. 9Process switching- Slowest method, every packet examined by CPU and all forwarding decisions are made by software
    - It will greatly degrade performance and is generally used only as a last resort or during troubleshooting.
  10. 10Route caching (Fast Switching)- Requiring RP and SE.
    RP must process the first flow's first packet to determinate the destination.
    SE listen the packet and to the resulting destination and set up a "shortcut" entry in the MLS cache. SE forward the same traffic's flow based on the shortcut entry.
  11. 11Topology based (CEF)- Using special hardware
    - With distinct RP and SE functions
    RP uses L3 routing information to populate a single DB of the entire known network topology. Efficient table lookup in hardware, consulted and forwarded at high rates by the SE.
  12. 12CEF- Cisco Express Forwarding
    - Topology based MLS is known as CEF
    - Routing process running on the switch download the current RT DB in to FIB (Forwarding Information Base) area of hardware.
  13. 13CAM table- Used for L2 switching
    - When a frame arrived the src add is learned and recorded in the CAM table
    - The port, vlan and timestamp of arrived both are recorded in the table
    - Entries are kept for 300 sec 5min
  14. 14CAM table commands#mac address-table aging-time (seconds)
    #mac address-table static (mac-add) vlan (vlan-id) interface (interface)
  15. 15CAM structureCAM use a key value (mac add) and lookup a resulting value (port or vlan-id). Lookup is fast and always based on an exactly key match of two values: 0 and 1 bits.
  16. 16TCAM structure- Extension of CAM concept
    - Also uses a table-lookup but is enhanced.
    - binary values (0,1) make ups a key into the table, but a mask value is also used to decide which bits of the key are relevant.
    - This effectively makes a key of three values (0,1,X)
  17. 17TCAM entries- Composed of Value, Mask and Result (VMR) combinations.
  18. 18Value- always 134 bits-quantities
    - SRC and DST addresses and other protocol information-all patterns to be matched.
    - The info concatenated to form the value depend on the type of ACE (up to a maximum of 134 bits).
  19. 19Mask- 134 bits quantities, in exactly same format.
    - Mask select only the value bits of interest.
  20. 20Result- Are numeric values that represent what action to take after the TCAM lookup occurs.
    - Result can be a permit or deny decision, an index value to a QoS policer, and so on.
  21. 21TCAMTCAM are always organized by mask, where each unique mask has eight value patterns associated with it. (8 values per mask eg. 4096 mask and 32,768 value patterns)
  22. 22LOULogical Operation Unit
    - If an ACE has a port operator (gt,lt,neq,range), the FMS compiles the TCAM entry to include the use of the operator and the operand in a LOU register.
  23. 23FMSFeature Manager Software
  24. 24Managing switching tables1.- Display information that sw has learned
    2.- Manage the size of the various switching tables to optimize performance
  25. 25To view the contents of the CAM tableSwitch# show mac address-table dynamic [ address mac-address | interface type
    mod/num | vlan vlan-id ]
    Switch# show mac address-table dynamic address 0050.8b11.54da
  26. 26To see the CAM table sizeSwitch# show mac address-table count
  27. 27CAM table entries can be cleared manuallySwitch# clear mac address-table dynamic [ address mac-address | interface type
    mod/num | vlan vlan-id ]
  28. 28TCAM operation- There is nothing to configure
    - Aware of is how the TCAM resources are being used
  29. 29TCAM utilization- TCAMs have a limited number of usable mask, value pattern, and LOU entries
    - if access lists grow to be large the TCAM can overflow.
    - The switch will generate syslog messages that flag the TCAM overflow situation as it tries to compile the ACL into TCAM entries.
  30. 30View TCAM utilizationSwitch# show platform tcam utilization
  31. 31Managing Switching Table SizesYou can select a preferred type of switching that, affects the relative size of the switching tables.
    To excel at Layer 2 switching, the CAM table should increase in size, whereas the FIB or routing table space should decrease and vice versa.
  32. 32SDMSwitching Device Manager
  33. 33Switching Device ManagerSDM is a flexibility feature that manages the memory partitions in a switch.
    Switch# show sdm prefer
  34. 34show sdm preferThe default template provides a balanced mix of Layer 2 (unicast MAC addresses, or the CAM table) and Layer 3 (IPv4 unicast routes, or the FIB table), in addition to IPv4 ACLs, and some minimal support for IPv6.
  35. 35Configure SDMSwitch(config)# sdm prefer "template"
    - The switch must then be rebooted for the new template to take effect
  36. 36SDM templates- access Access bias
    - default Default bias
    - dual-ipv4-and-ipv6 Support IPv4 &IPv6
    - routing Unicast bias
    - vlan VLAN bias
  37. 37DefaultWhen you unbox a brand new switch, this template will be the enabled template. It provides a mix of unicast, connected, and host routes.
  38. 38RoutingAs one example, you would enable this template if the device is performing routing in the distribution or core of the network. The device is able to carry numerous routes, but only for IPv4
  39. 39AccessThe access template maximizes system resources for access control lists (ACLs) to accommodate many ACLs
  40. 40VLANWhen you enable this template, you allocate most of the table space to Layer 2 unicasts. You would use this template when you have large subnets with many MAC addresses
  41. 41Dual IPv4 and IPv6You would enable this template if you want to turn on the IPv6 capabilities of the device. When enabling this template, you have to choose between
    - default
    - routing
    - VLAN
  42. 42Switch(config)# ipv6? % Unrecognized commandSwitch(config)# sdm prefer dual-ipv4-and-ipv6 default

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300-115 (Part I: Designing Campus Network) CCNP SWITCH 300-115 Fichas sobre Part 1 - Chapter 2 (Switch operation), creado por Luis Domínguez el 11/03/2018.
Creado por
Luis Domínguez
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ccnp switch
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