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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. What duplex setting does 802.11 use and why?
Configure the timer on the AVG and let it propagate
Half because transmitting and receiving stations use the same frequency
By sending a gratuitous ARP
Critical...used most often for IPT

2. if the switchport is part of an etherchannel - Where is the network assigned
3 seconds. Holdtime =3 hellos + 1
To the virtual port-channel interface
If three are missed in a row - the neighbor is considered down and the data for that neighbor is aged
Use the spanning-tree root macro

3. What is a proxy arp?

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4. what do multilayer switches do?
26-byte header - 4-byte trailer with CRC
1- enable MST - 2-enter MST config mode - 3-assign region name and region configuration rev - 4-map vlans to an MSTI - 5-show pending changes - 6- commit by exiting
Discarding - learning - forwarding
Both layer 2 switching and IVR

5. What is an untrusted port under dhcp snooping?
On the left as you face the connector
Plain text or md5
Any dhcp reply coming from an untrusted port is discarded and the offending port is put in errdisable
Src-dst-ip

6. What is a BSS?
The standby becomes active and stays active by default. Preemption can be configured
Using a single WAP to centralize access and control over a group of wireless devices.
Transmits keystrokes from phone and commands from CCM
They should be an unconditional Etherchannel because the WLC can't negotiate a channel.

7. How do you configure DAI for statically configured IP addresses?
By using an Ether-IP tunnel
By an ARP access list that defines the permitted bindings
Port with alternative path to root less desirable than root
Incoming frames dropped - but MACs learned

8. What does the SP do?
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
Yes
Variation in delay
1-65535 (def 32768) lower priority - higher probability

9. How many tunnels exist between the LAP and WLC?
They are locally significant on an interface. HSRP1 on one VLAN is different from HSRP1 on another
Hosts within a secondary can communicate with each other and with the primary - but not with another secondary vlan
When the AP uplinks to an Ethernet network.
2 - one for control messages and one for data

10. How does packet forwarding work
Can hear only BDPUs
On ports where you never expect to find a root bridge for a VLAN
All user ports that have portfast enabled
Arp for local subnet - if on different subnet - will arp for dgw

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

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12. What do you need to determine to use MSTP?
They are locally significant on an interface. HSRP1 on one VLAN is different from HSRP1 on another
Within a single MST region - an IST instances runs to work out a loop free topology between links where CST meets the region boundary and all switches in the region. It runs at the boundary.
Create 2 hsrp groups - each with the active router being different switches - then have clients point to each
The number of STP instances needed ot support the desired topologies and whether to map a set of VLANs to each instance

13. If one end of an Etherchannel (either type) is set to on and the channel doesn't form - what should you check?

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14. What are the 2 choices for VLANs with IPT?
Promiscuous and host
They must be carried over a voice VLAN (VVID) or over a regular data VLAN (ie. The native VLAN or the PVID)
Virtual Router Redundancy Protocol - pretty much the same as HSRP
Packets are discarded due to an ACL or policy action

15. How often are BDPUs sent?
2 seconds (def)
On all switches in network to enable RLQ request and reply
Via an 802.1Q trunk or a single VLAN access port
The campus network's backbone

16. How do IP phones communicate with each other?
Once the CCM gives them the parameters - they use RTP
LACP port priority
Aggregation - high L3 throughput - security and policy based connectivity functions through access lists and packet filters - QoS - scalable high-speed links
1-1005 (1 and 1002-1005 are reserved)

17. How does IPT behave when the voice VLAN is in untagged mode?
Disabled - init - listen - speak - standby - active
Real-time functions such as beacons and probes - encryption and interactions with the client at L2
Data and voice over native vlan - no QOS but still uses 802.1p trunk
1 per segment

18. What are the characteristics of the core layer
It's a router that maintains routes (static or dynamic) - and populates the FIB
Very high L3 throughput - no access lists or port filtering - redundancy and resilience - advanced QoS
Port is forced to never authorize any connected client
By name - config revision - and instance to vlan mapping table

19. How do VRRP routers handle preemption?
1 per segment
After another forwarding delay - the port can send and receive data frames - collect MAC addresses - and send and receove BDPUs
Yes to both
On by default

20. What is a baby giant frame?
Backbonefast uses RLQ to determine if upstream switches have stable connections to root bridge
A path is pre-arranged for priority along the complete path from source to destination using the RSVP protocol.
Frames that barely exceed 1518B or 1622B due to headers
Checks the sender's ip in all arp requests and checks the sender's IP against target IP in all replies

21. What happens if both 802.1D and RSTP BDPUs are received?
It is enabled by default on all CEF capable switches
Hold time is 3xhello. A skew time of 256ms-routerpriority)/256ms is added
Only for trusted Cisco gear - especially phones
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

22. What are the 5 STP port roles?
Used when ACLs specify port ranges...used by TCAM
Root - designated - blocking - alternate - forwarding (host)
Change in trunk encap
80% of the user traffic should stay in the VLAN

23. What are the steps to configure a PAgP port channel?
A MAC is seen on a different port
One router is the active virtual gateway - has highest priority or IP in group - answers all ARP requests and gives MAC based on load balancing
1-(opt) configure load balancing - 2-select the interface(s) - 3-assign the protocol - 4-select the mode and submode
No

24. How does a DHCP server send WLC addresses?
Protects STP when a physical malfunction only allows traffic in 1 direction - even though the link shows as up (cisco proprietary)
Option 43
1 IP subnet
Switched Virtual Interface - an L3 address can be assigned to a logical interface that represents an entire VLAN - which becomes the DGW for that VLAN

25. What is NSF?
LACP port priority
Nonstop forwarding is an interactive method focusing on rebuilding the RIB after SUP switchover
Trusted ports
802.1x with EAP over LAN (EAPOL)

26. What is common spanning tree (CST)?
Single instance of STP for all VLANs. BDPUs are sent over trunks using the native VLAN with untagged frames. Dot1q based
Can hear only BDPUs
Connects to a router - firewall - or gateway. Can communicate with anything else connected to the primary or any secondary. Ignores pvlan config
Only a single host connects . If one BDPU is received - it is no longer an edge port

27. 802.11a
Single instance of STP for all VLANs. BDPUs are sent over trunks using the native VLAN with untagged frames. Dot1q based
By using a trunk link
Globally
Up to 54Mbps - not cross-compatible - 12 to 23 clean channels - 5.8 Ghz

28. How does ISL handle COS?
The port uses 802.1x exchange to move from unauthorized to authorized. Requires app on client
The frame tag contains a 3 but portion tagged from 0 (low) to 7 (high)
During the time that the FIB entry is in CEF glean waiting for ARP entries - subsequent packet to that host are dropped to keep input queues from filling
Low cost - high density ports - multiple scalable uplinks - vlans - traffic and protocol filtering and QoS

29. How does a Cisco IP phone connect upstream?
Disabled - blocking - listening - learning - forwarding
Via an 802.1Q trunk or a single VLAN access port
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
It updates the L2 headers with the proper src and dst MAC - L3 TTL - L3 checksum - and L2 checksum information

30. What are the 3 redundant supervisor modes?
Only for trusted Cisco gear - especially phones
Causes switch to actively determine whether alternative paths exist to root bridge in case ther eis an indirect failure
All non-edge ports are discarding. After the root bridge is identified - the port with superior BDPU becomes root
RPR - RPR+ - and SSO

31. What is the SDM?
Switching Database Manager - configures and prunes TCAM partitions
One router is the active virtual gateway - has highest priority or IP in group - answers all ARP requests and gives MAC based on load balancing
Virtual Router Redundancy Protocol - pretty much the same as HSRP
Prevents the dhcp binding DB from being checked.

32. Where is the QoS trust boundary usually configured on an IP phone?
26-byte header - 4-byte trailer with CRC
The wireless clients communicate directly with no other means of connectivity such as a WAP
Usually QoS from VOIP but not PC dataa
Root

33. How does RSTP identify a topology change?
Gateway load balancing protocol - cisco proprietary
1- trunking mode - 2-trunk encapsulation - 3-native VLAN - 4-allowed VLAN
Only when a nonedge port transitions to forwarding
Flash override (class 4)

34. What is an SVI?
Port stays up - packets from violating MACs dropped - no logging
Switched Virtual Interface - an L3 address can be assigned to a logical interface that represents an entire VLAN - which becomes the DGW for that VLAN
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.
No

35. On what scope is DAI enabled?
Per VLAN
Routers at the distribution layer become the bottlenecks or broadcast or multicast traffic slows the switches in the switch block
Use the spanning-tree root macro
No shut

36. What is the cost of a 10Gbps link?
Trunk
Group (0-255) - priority (1-254 254 is highest - 100 default)
Forces the router to wait for a period of time after the switch is reloaded before attempting to overthrow
2

37. How often are VRRP advertisements sent?
1 second. Backup routers can learn the interval from the master
The active router. All other routers are in backup state
The station must wait until the frame in progress has completed - then wait a random amount of time before transmitting
The distribution layer should have only L3 links

38. What is a bridge ID made up of?
3 seconds. Holdtime =3 hellos + 1
Bridge priority and MAC
900 MHz - 2.4Ghz - and 5-6GHz
They disguise the origin of an attack

39. Where is bdpu guard enabled?
All user ports that have portfast enabled
Promiscuous and host
Notifies upstream neighbors by sending multicasts on behalf of hosts at the interval of the max update rate parameter.
An instance of RSTP running for each VLAN on the switch. Changing from PVST to RPVST+ is disruptive

40. What is RPR?
The L3 forwarding engine can't forward the packet in hardware because there is no L2 next-hop address - so the packet is sent to the L3 engine to generate the ARP response
Route processor redundancy - redundant sup is partially booted and initialized and must reload module in the switch and init all sup functions
On by default
Interim solution - uses same hardware as WEP - but uses TKIP encryption

41. How many virtual MACs can GLBP have?
Switch(config-if)# vrrp xx where xx= group number
Up to 4 can be used in a group. Called active virtual forwarders (AVF)
Protects STP when a physical malfunction only allows traffic in 1 direction - even though the link shows as up (cisco proprietary)
Only for the offending VLAN on the port

42. What ILP mode are all ports in by default?
Multicasts to 224.0.0.18 (VRRP)
Best effort delivery - integrated services model - and differentiated services model
Auto mode
1 -2 -5.5 and 11 Mbps - Channels 1/6/11 - 2.4Ghz

43. What is DSCP codepoint AF21(18)?
Aggregation - high L3 throughput - security and policy based connectivity functions through access lists and packet filters - QoS - scalable high-speed links
Immediate (class 2)
Packets must be sent to the L3 engine for further processing
Per-port or globally for all fiber-optic ports. Can be enabled globally - but will only affect fiber ports

44. What are the PAgP negotiation modes
All ARP packets that arrive on untrusted ports are inspected.
On (all ports channel) - auto (channels when asked) - and desirable(actively asks to form a channel)
The number of times the entry has been updated since the table was generated
During the time that the FIB entry is in CEF glean waiting for ARP entries - subsequent packet to that host are dropped to keep input queues from filling

45. How do you enable CEF?
By short-circuiting the max age timer
It is enabled by default on all CEF capable switches
Use sh interface on the interface and look for error counts > 10
Lowest cumulative cost to root

46. How much overlap should WAPs have?
Because each frame is checked
10-15%
RPR - RPR+ - and SSO
Port that connects to another switch and becomes a designated port

47. What is dynamic desireable?
Sends a voltage across the receive pairs to detect a 25k ohm resistance
One that can be detected on a switch interface (ie. Up/down)
Port with alternative path to root less desirable than root
The port asks the other end to trunk

48. RSTP alternate port
A packet can't be switched in hardware with the FIB and must go to the L3 engine
The configureable UDLD interval must be less than max age plus two intervals of forward delay
Used when ACLs specify port ranges...used by TCAM
Port with alternative path to root less desirable than root

49. What is the default MTU?
1500B
Variation in delay
Prevents the dhcp binding DB from being checked.
Auto mode

50. One vlan should =
1 IP subnet
Isl - dot1q - negotiate (default)
Makes use of the DHCP snooping database and static ip source binding entries. If enabled - switch will test addresses
Tracks of BDPUs on nondesignated ports. When those BDPUs stop coming - the port is put into loop-inconsistent state and blocks