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CCNP Switch Deck

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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 I s distributed CEF (dCEF)?
Critical...used most often for IPT
CEF is distributed completely among multiple L3 forwarding engines.
For hosts that doesn't understand routing - the DGW is configured to reply with its own mac
A port can only forward or relay BDPUs - but can't receive them - disabled by default - enabled per-port - blocks port when superior BDPUs are received

2. Define HSRP
Per-port or globally for all fiber-optic ports. Can be enabled globally - but will only affect fiber ports
Switchpotrt nonegotiate
RADIUS
Host Standby Router protocol. Cisco proprietary. Switch is either active - standby - or listen

3. What is GLBP weight?
1-name the chain - 2-establish a key number - 3-create the key string - 4-apply the chain to the string
By default weight is 100. Can be made dynamic per interface
It is enabled by default on all CEF capable switches
When a specific interface is tracked - HSRP reduces it's priority after a specified interval.

4. How does DSCP handle IP precedence?
Collision domain
If three are missed in a row - the neighbor is considered down and the data for that neighbor is aged
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.
5 classes with 3 drop precedences

5. What is the bridge priority range?
CEF is distributed across multiple L3 forwarding engines - typically on Catalyst 6500 line cards each having only a subset
0-65535 (def 32768) lower=better
5 (0-4 with 4 being the highest)
If a unidirectional link is detected - the switch doesn't try to reestablish the link. ULD msgs are sent once/sec for 8 seconds - then the port is err-disabled

6. What happens when switches receive a configuration BDPU?
Sends a test tone on the transmit pair. If a device is detected - CDP is used to narrow down the power class.
Group (0-1023) priority (1-255 higher better def 100)
They shorten their bridge table aging times from default (300sec) to the fowarding delay (15 sec)
3 seconds. Holdtime =3 hellos + 1

7. What does the src-mac option do when checking ARP replies
Checks the source MAC in the header against the sender MAC in the ARP reply
Can hear only BDPUs
Checks the destination MAC in the header against the target MAC in the ARP reply
Each physical interface has a different IP address. All physical interfaces point to a virtual interface called the standby address or VIP

8. What is an IST instance?
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.
Promiscuous and host
Backbonefast uses RLQ to determine if upstream switches have stable connections to root bridge
Frames are forwarded

9. RSTP forwarding state
300 sec by default
Notifies upstream neighbors by sending multicasts on behalf of hosts at the interval of the max update rate parameter.
The standby becomes active and stays active by default. Preemption can be configured
Frames are forwarded

10. What is the DIFS?
Port with best root path cost
Manages addition - deletion and renaming VLANs across the network
The DCF interframe space- the random backoff time before a wireless set can transmit
Either desirable or auto mode

11. One vlan should =
1- trunking mode - 2-trunk encapsulation - 3-native VLAN - 4-allowed VLAN
1 IP subnet
Admin down
Root

12. On what scope is DAI enabled?
LACP port priority
By name - config revision - and instance to vlan mapping table
Frames are forwarded
Per VLAN

13. can root guard and udld be used together?
Yes
Incoming frames dropped - but MACs learned
Trusted or untrusted
Switches make an effort to move packets as quickly as possible

14. What are the 3 trunk switchport modes?
PAgP (Cisco proprietary) and LACP (standards-based)
When a client roams between Aps in different subnets
Turn on port security
Trunk - dynamic auto - dynamic desireable (default)

15. What are the 3 unlicensed frequencies?
900 MHz - 2.4Ghz - and 5-6GHz
Isl - dot1q - negotiate (default)
Regions and instances
0007.b4xx.xxyy where xx.xx is six 0 bits followed by a 10-bit GLBP group numberr. Yyyy is the virtual forwarder number

16. How are RSTP point to point ports determined?
Automatically by duplex mode in use. Full duplex are point ot point. Half duplex ports use traditional 802.1D convergence is used.
With the skinny protocol
Port that connects to another switch and becomes a designated port
1/2 and 3/6

17. What is UDLD normal mode?
On by default
Data goes over native vlan - voice goes over specified VLAN - voice QOS is 802.1p
The MST instance (MSTI) runs alongside the IST and represents an STP instance
If a unidirectional link is detected - the port continues normally - but the port is marked as undetermined and a syslog is generated

18. What is a discard adjacency?
The number of STP instances needed ot support the desired topologies and whether to map a set of VLANs to each instance
The port uses 802.1x exchange to move from unauthorized to authorized. Requires app on client
All L2 connectivity should be contained within the access layer.
Packets are discarded due to an ACL or policy action

19. At what layer does EAPOL run?
Promiscuous and host
Because each frame is checked
L2
MAC of the end device

20. RSTP root port
Port with best root path cost
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
Every hello interval regardless of whether BDPUs are received from root - allowing any switch to take an active role maintaining the topology
The configureable UDLD interval must be less than max age plus two intervals of forward delay

21. Does GLBP allow preemption?
Yes
Effectively stops STP on filtered ports
Port is forced to never authorize any connected client
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

22. What is a proxy arp?

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23. How does every VRRP command begin?
Incoming frames are dropped (combination of disabled - blocking - and listening)
Stateful switchover - redundant sup is fully booted and init'd. Both start and run config are synched as is L2 information - and switchinterfaces.
134 bits - consisting of source and destination addresses and protocol information from the packet or frame
Switch(config-if)# vrrp xx where xx= group number

24. What does the version number indicate when looking at CEF entries?
Edge - root - and point to point
Cisco ILP and 802.3af
The number of times the entry has been updated since the table was generated
Used to switch packets destined for the null interface

25. Can loop guard and udld be used together?
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
Yes
Via an 802.1Q trunk or a single VLAN access port
Real-time Transport Protocol

26. What does the standby HSRP router do?
Create 2 hsrp groups - each with the active router being different switches - then have clients point to each
Only a single host connects . If one BDPU is received - it is no longer an edge port
Only the standby monitors the hello messages from the active router
Packets are discarded due to an ACL or policy action

27. CAM table entries are purged when....
Using a single WAP to centralize access and control over a group of wireless devices.
Used to switch packets that can't be forwarded normallly due to an encapsulation failure - unresolved address - unsupported protocol - etc.
A MAC is seen on a different port
300 sec

28. What is the default MTU?
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
Used when ACLs specify port ranges...used by TCAM
1500B
Two distribution switches that aggregate one or more access switches

29. What is the STP learning state?
Cisco recommends only on the root bridge
After forwarding delay - port can learn new MAC addresses
They should be an unconditional Etherchannel because the WLC can't negotiate a channel.
The port asks the other end to trunk

30. 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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31. What is a null adjacency?
The link status stays up - but something between them has failed or is filtering traffic
Used to switch packets destined for the null interface
By using a hash of a key string
Trusted ports

32. What contains the next-hop entries?
By an ARP access list that defines the permitted bindings
Real-time Transport Protocol
FIB
Used when there are 1 or more VLANs mapped to a single STP instance

33. What is dhcp snooping rate limiting?
Limits the number if dhcp requests on a port
Bridge priority and MAC
Via an 802.1Q trunk or a single VLAN access port
A point to point port type but the neighboring device runs traditional 802.1D STP

34. What is an MST instance?
Between interfaces that are assigned to L2 VLANs or L2 trunks
The MST instance (MSTI) runs alongside the IST and represents an STP instance
Needs hardware upgrade over WEP - uses AES encryption
Can send and receive BDPUs

35. What is best effort delivery QOS?
Differentiated services
1-(opt) set system priority - 2-select interface(s) - 3-assign the protocol - 4-set the mode - 5-(opt) set the port priority
Each frame transmits its expected duration time
Switches make an effort to move packets as quickly as possible

36. How many links can be used in an EtherChannel?
Missed beacons - dropped packets (max retry) - weak signal (data rate switches down) - an AP periodicallytries to find a stronger signal
2-8 FE - GE - or 10GE are bundled.
802.1w
RADIUS

37. How does GLBP work?
Routers are assigned to common GLBP group. All routers can be active and can load balance
Per VLAN
FIB
By encapsulating each frame in a header and trailer

38. What does the epoch number indicate when looking at cef entries?
Must be same type - speed - VLAN(s) - native vlan - pass the same set of vlans -duplex - and spanning tree settings
The number of times the CEF table has bee flushed and regenerated as a whole
Isolated and community
The number of STP instances needed ot support the desired topologies and whether to map a set of VLANs to each instance

39. Where is UDLD enabled?
Port
All fiber-optic links between switches (must be enabled on both ends)
The station must wait until the frame in progress has completed - then wait a random amount of time before transmitting
A router keeps a routing table and an ARP table. The FIB combines them for every next-hop entry

40. What is the STP hello timer?
Automatically by duplex mode in use. Full duplex are point ot point. Half duplex ports use traditional 802.1D convergence is used.
Time between BDPUs sent by root bridge. Default of 2 seconds
63 kbps
Packets must be sent to the L3 engine for further processing

41. Where is the QoS trust boundary usually configured on an IP phone?
Data and voice over native vlan no QOS and no 802.1p trunk
19
Between interfaces that are assigned to L2 VLANs or L2 trunks
Usually QoS from VOIP but not PC dataa

42. What is SSO?

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43. What is unique about HSRP group numbers?
The master router can share the VIP
They are locally significant on an interface. HSRP1 on one VLAN is different from HSRP1 on another
The time interval that a switch stores a DBPU before discarding it. Default 20 seconds
Gateway load balancing protocol - cisco proprietary

44. How does IPT behave when the voice VLAN is in dot1p mode?
19
1-(opt) configure load balancing - 2-select the interface(s) - 3-assign the protocol - 4-select the mode and submode
Data goes over native vlan - voice goes over VLAN0 - voice QOS is 802.1p
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. What is the access layer best practice?
Option 43
Packets must be sent to the L3 engine for further processing
Route once - switch many
All L2 connectivity should be contained within the access layer.

46. How often are CAM table entries aged?
A private VLAN can be logically associated with a special secondary vlan
Each peer sends and receives hellos. Def hello is 3 sec - def hold is 10 sec
Immediate (class 2)
300 sec

47. How does an LAP bind with a WLC?
On all switches in network to enable RLQ request and reply
80% of the user traffic should stay in the VLAN
3 seconds. Holdtime =3 hellos + 1
By brining up a tunnel between them to carry 802.11 related messages and client data.

48. How is an RSTP edge port configured
By using an Ether-IP tunnel
Used to switch packets destined for the null interface
The station can transmit immediately and wait for an ack
With portfast

49. Where is loop guard enabled?
If a unidirectional link is detected - the port continues normally - but the port is marked as undetermined and a syslog is generated
Both layer 2 switching and IVR
MST attributes must be manually entereed on each switch in the region. They don' t propagate like VTP.
All nondesignated ports - but ok for all ports

50. What is a bridge ID made up of?
Real-time functions such as beacons and probes - encryption and interactions with the client at L2
Route processor redundancy - redundant sup is partially booted and initialized and must reload module in the switch and init all sup functions
Each frame transmits its expected duration time
Bridge priority and MAC