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CCNP Switch Deck

Instructions:

Answer 50 questions in 15 minutes.
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Match each statement with the correct term.
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This is a study tool. The 3 wrong answers for each question are randomly chosen from answers to other questions. So, you might find at times the answers obvious, but you will see it re-enforces your understanding as you take the test each time.

1. How should the switch port to which a LAP be configured?
Port stays up - but packets from violating MACs are dropped. Switch logs violating packets
Access
By short-circuiting the max age timer
Roughly 2000

2. At what layer should the WLC be connected?
300 sec by default
By sending a gratuitous ARP
Distribution
Immediate (class 2)

3. What is the default MTU?
Globally
Feature Manager - after the ACL is created - the FM compiles the ACEs into the table
Real-time functions such as beacons and probes - encryption and interactions with the client at L2
1500B

4. How does backbonefast determine whether alternative paths exist?
If the client maintains the same IP address as it roams between Aps. All must have same VLAN - SSID - and subnet
1- inferior BDPU on blocked-considered alternative - 2-inferior on root-all blocked ports considered alternate - 3-if inferior arrives on root and no blocked ports - assumes loss of connectivity to root
The wireless clients communicate directly with no other means of connectivity such as a WAP
No

5. How should the switch port to which a WLC be configured?
Trunk
Only when a nonedge port transitions to forwarding
Port with alternative path to root less desirable than root
Half because transmitting and receiving stations use the same frequency

6. What is DSCP codepoint AF41(34)?
Incoming frames dropped - but MACs learned
Flash override (class 4)
300 sec
Per-port or globally for all fiber-optic ports. Can be enabled globally - but will only affect fiber ports

7. What is a VRRP group?
The same as a standby group in HSRP
1 IP subnet
Time between BDPUs sent by root bridge. Default of 2 seconds
The MST instance (MSTI) runs alongside the IST and represents an STP instance

8. How does the standby handle ARP issues after it becomes active?
By sending a gratuitous ARP
Port with redundant - but less deisrable connection to a segment. Possibly root candidate
Will trunk if asked
The station must wait until the frame in progress has completed - then wait a random amount of time before transmitting

9. What can the Etherchannel hash use?
Configure the timer on the AVG and let it propagate
Source IP - dest IP - combination of source and dest IP - source and dest MAC - or TCP/UDP port numbers
134 bits - consisting of source and destination addresses and protocol information from the packet or frame
Half because transmitting and receiving stations use the same frequency

10. Which 4 things must be agreeable to trunk?
Causes switch to actively determine whether alternative paths exist to root bridge in case ther eis an indirect failure
80% of the user traffic should stay in the VLAN
Connects with SONET or SDH
1- trunking mode - 2-trunk encapsulation - 3-native VLAN - 4-allowed VLAN

11. How does IPT behave when the voice VLAN is in untagged mode?
Data and voice over native vlan - no QOS but still uses 802.1p trunk
Tracks of BDPUs on nondesignated ports. When those BDPUs stop coming - the port is put into loop-inconsistent state and blocks
If a proposal is received - the recipient isolates - all nonedge ports blocked until proposal sent causing neighbors to synch - which propagates out in waves
Connects to a router - firewall - or gateway. Can communicate with anything else connected to the primary or any secondary. Ignores pvlan config

12. What feedback mechanism does wireless use?
When a wireless station transmits a frame - the receiving one must send an ack
Cisco recommends only on the root bridge
0007.b4xx.xxyy where xx.xx is six 0 bits followed by a 10-bit GLBP group numberr. Yyyy is the virtual forwarder number
1- trunking mode - 2-trunk encapsulation - 3-native VLAN - 4-allowed VLAN

13. What does the rewrite engine do?
Distribution layer
It updates the L2 headers with the proper src and dst MAC - L3 TTL - L3 checksum - and L2 checksum information
Roughly 2000
CEF is distributed across multiple L3 forwarding engines - typically on Catalyst 6500 line cards each having only a subset

14. On what scope is DAI enabled?
Per VLAN
The priority is a 2 byte value followed by the MAC that decides which ports are actively participating in Etherchannel (lower=higher priority)
If a unidirectional link is detected - the port continues normally - but the port is marked as undetermined and a syslog is generated
Via an 802.1Q trunk or a single VLAN access port

15. When looking at the sh spanning tree output - What does P2P denote?
900 MHz - 2.4Ghz - and 5-6GHz
The TOS field in the header is used. 2 methods 3 bits or 6 bits
CEF is distributed across multiple L3 forwarding engines - typically on Catalyst 6500 line cards each having only a subset
A point to point port type

16. What is the distribution layer best practice?
CEF is distributed completely among multiple L3 forwarding engines.
Connects to a host on an isolated or community vlan. Communicates only with promiscuous port or ports on same community vlan
The distribution layer should have only L3 links
A group of wireless devices that share a common SSID

17. How should backbonefast be configured?
When a wireless station transmits a frame - the receiving one must send an ack
The redundant SUP is booted and sup and route engine is init'd. No L2 or L3 functions are started. Allows switchports to retain state
On all switches in network to enable RLQ request and reply
Hashing algorithm

18. What does the SP do?
One that can be detected on a switch interface (ie. Up/down)
The number of times the CEF table has bee flushed and regenerated as a whole
Very high L3 throughput - no access lists or port filtering - redundancy and resilience - advanced QoS
Listens to the first packet going to router and away from the router. If it can switch in both directions - it learns a shortcut path so subsequent packets can be switched without the RP

19. How much BW does a PSTN connection use?
Switch(config-if)# glbp xx where xx = group number
Best effort delivery - integrated services model - and differentiated services model
Per-port or globally for all fiber-optic ports. Can be enabled globally - but will only affect fiber ports
63 kbps

20. How do you renable an err-disable port by default?
Dynamic WEP keys that change periodically
1- inferior BDPU on blocked-considered alternative - 2-inferior on root-all blocked ports considered alternate - 3-if inferior arrives on root and no blocked ports - assumes loss of connectivity to root
Notifies upstream neighbors by sending multicasts on behalf of hosts at the interval of the max update rate parameter.
Manually

21. If the WLC connects to an Etherchannel - how should the channel be configured and why?

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22. One vlan should =
By brining up a tunnel between them to carry 802.11 related messages and client data.
1 IP subnet
Between interfaces that are assigned to L2 VLANs or L2 trunks
From the DHCP snooping database or from static entries

23. In a converged fabric - which switch(es) send config BDPUs?
On all switches in network to enable RLQ request and reply
Every switch and router in a network must be configured with appropriate QoS features and policies
Root
1500B

24. How does ISL do trunking?
134 bits - consisting of source and destination addresses and protocol information from the packet or frame
VTP server for domain null with no password or secure mode
By encapsulating each frame in a header and trailer
Because each frame is checked

25. Automatically configure STP timers
Use the spanning-tree root macro
Normal and aggressive
Root - designated - blocking - alternate - forwarding (host)
The port will operate under 802.1D rules. If they are received on the same port - it will run 802.1D until the migration delay expires

26. Can two switches in the auto(PAgP) or passive (LACP) mode create a channel? Why?
The configureable UDLD interval must be less than max age plus two intervals of forward delay
No because they only participate if asked
Switchpotrt nonegotiate
L2

27. What types of ports autonegotiate?
FE and GE
The time interval that a switch stores a DBPU before discarding it. Default 20 seconds
Will trunk if asked
A VLAN that spans the entire fabric

28. What are TCAM entries composed of?
Trunk
RPR - RPR+ - and SSO
Value - mask - and result (VMR) combinations
Two distribution switches that aggregate one or more access switches

29. What is the traditional MLS view of switching?
2 seconds
Route once - switch many
On by default
Distributed coordinion function - the use of timers to prevent wireless collisions

30. Where is UDLD enabled?
All fiber-optic links between switches (must be enabled on both ends)
1- enable qos - 2-define qos parameters to be trusted - 3-make trust conditional - 4-instruct IP phone how to extnd boundary
Host Standby Router protocol. Cisco proprietary. Switch is either active - standby - or listen
Src-ip - dst-ip - src-dst-ip - src-mac - dst-mac - src-dst-mac - src-port - dst-port - src-dst-port

31. Where is bdpu guard enabled?
All user ports that have portfast enabled
0000.0c07.acxx where xx is the group number as a 2-digit hex value
PAgP (Cisco proprietary) and LACP (standards-based)
Nonstop forwarding is an interactive method focusing on rebuilding the RIB after SUP switchover

32. What are the 5 STP states?
Only for the offending VLAN on the port
Can hear only BDPUs
The time interval that a switch stores a DBPU before discarding it. Default 20 seconds
Disabled - blocking - listening - learning - forwarding

33. How does a LAP and a WLC authenticate between each other?
If the switch or the powered device doesn't suport power class discovery
Differentiated services code point
Using digital certificates
On root - because the root bridge propagates timers with config BDPU

34. How do you configure DAI for statically configured IP addresses?
By an ARP access list that defines the permitted bindings
That they aren't using the same frequencies.
By default weight is 100. Can be made dynamic per interface
Distributed coordinion function - the use of timers to prevent wireless collisions

35. How do you disable DTP when you configure both ends of the ISL manually?
16 - of which up to 8 are active. The others are in standby
Any dhcp reply coming from an untrusted port is discarded and the offending port is put in errdisable
Switchpotrt nonegotiate
Some unused bits are used to allow a port to identify its role and state. Also the BDPUs state that they are V2 BDPUs

36. What is the RSTP default hello interval?
Using a single WAP to centralize access and control over a group of wireless devices.
A point to point port type
Yes
2 seconds

37. What is the switch block?
First configure a L3 interface in same VLAN as clients - then use the ip helper-address command to ID the DHCP server
Two distribution switches that aggregate one or more access switches
The point at which a switch decides to trust incoming Qos. Usually at boundary with ISP
Between any type of interface as long as the interface can have an L3 address assigned

38. How does every HSRP config command begin?
Route processor redundancy - redundant sup is partially booted and initialized and must reload module in the switch and init all sup functions
Enables switches at the end of the spanning tree branches to have a functioning root port while keeping 1 or more redundant potential ports in blocking mode. When the main fails - the other comes up.
Cisco ILP and 802.3af
Switch(config-if)# standby xx where x= group number

39. What are the gotchas for uplinkfast?

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40. RSTP discarding state
By configuring every switch port to have an expected and controlled behavior
Incoming frames are dropped (combination of disabled - blocking - and listening)
0-255
A key string of up to 8 characters is sent. Default is cisco.

41. How are VACLs applied
To a VLAN and not to a VLAN interface (SVI)
Based on priority (0-255). Default is 100. Highest IP is tie breaker
Cisco ILP and 802.3af
The number of STP instances needed ot support the desired topologies and whether to map a set of VLANs to each instance

42. How often are HSRP hellos sent?
Should be used on access switches - can't be used on root - keeps enabled switch from becoming root by raising priority of switch and all ports - making them undesirable
Low cost - high density ports - multiple scalable uplinks - vlans - traffic and protocol filtering and QoS
On the left as you face the connector
3 seconds. Holdtime =3 hellos + 1

43. How does RSTP identify a topology change?
The port asks the other end to trunk
Only when a nonedge port transitions to forwarding
Priority (class 1)
Cisco recommends only on the root bridge

44. RSTP BPDU structure
Isl - dot1q - negotiate (default)
1- inferior BDPU on blocked-considered alternative - 2-inferior on root-all blocked ports considered alternate - 3-if inferior arrives on root and no blocked ports - assumes loss of connectivity to root
0-65535 (def 32768) lower=better
Some unused bits are used to allow a port to identify its role and state. Also the BDPUs state that they are V2 BDPUs

45. What does the skinny protocol do?
Transmits keystrokes from phone and commands from CCM
1- trunking mode - 2-trunk encapsulation - 3-native VLAN - 4-allowed VLAN
Automatically by duplex mode in use. Full duplex are point ot point. Half duplex ports use traditional 802.1D convergence is used.
Trunk

46. WEP encryption
TCAM
The frame tag contains a 3 but portion tagged from 0 (low) to 7 (high)
Switch(config-if)# vrrp xx where xx= group number
Weak key rotation

47. What does the static keyword do when applying an arp ACL?
Gateway load balancing protocol - cisco proprietary
Compatible with 802.11b - up to 54Mbps in 12 data rates - 3 channels - 2.4Ghz
Using a mobility exchange message
Prevents the dhcp binding DB from being checked.

48. What does UDLD do?
No
Switches make an effort to move packets as quickly as possible
All nondesignated ports - but ok for all ports
Protects STP when a physical malfunction only allows traffic in 1 direction - even though the link shows as up (cisco proprietary)

49. How does dot1q do trunking?
Immediate (class 2)
Embeds the tag within the frame
All nondesignated ports - but ok for all ports
Port with redundant - but less deisrable connection to a segment. Possibly root candidate

50. How does HSRP port tracking work?

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