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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.
Don't refresh. All questions and answers are randomly picked and ordered every time you load a test.

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. RSTP forwarding state
Isl - dot1q - negotiate (default)
Frames are forwarded
The MST instance (MSTI) runs alongside the IST and represents an STP instance
0000.0c07.acxx where xx is the group number as a 2-digit hex value

2. What is jitter?
Variation in delay
A private VLAN can be logically associated with a special secondary vlan
16 - IST gets MSTI 0 - 1-15 are available for use. MSTIs are locally significant to the MST region
The topology is pre-populated by downloading the topology DB into the FIB and dynamically updated. Called Cisco Express Forwarding

3. What is DSCP?
Group (0-255) - priority (1-254 254 is highest - 100 default)
Differentiated services code point
1 IP subnet
Forces the router to wait for a period of time before attempting overthrow

4. What is the traditional MLS view of switching?
16 - of which up to 8 are active. The others are in standby
They are locally significant on an interface. HSRP1 on one VLAN is different from HSRP1 on another
On root - because the root bridge propagates timers with config BDPU
Route once - switch many

5. How do you configure a DHCP gateway?
19
First configure a L3 interface in same VLAN as clients - then use the ip helper-address command to ID the DHCP server
Switch(config-if)# vrrp xx where xx= group number
With portfast

6. What are the characteristics of the distribution layer?
Hashing algorithm
Aggregation - high L3 throughput - security and policy based connectivity functions through access lists and packet filters - QoS - scalable high-speed links
The time interval that a switch stores a DBPU before discarding it. Default 20 seconds
Global config (vlan - vtp mode - and vtp domain) and VLAN DB mode commands. Global config is preferred because VLAN DB mode commands are legacy

7. How does UDLD work?
Sends special layer 2 UDLD frames and expects an echo. Both ends must be configured for UDLD
Only when a nonedge port transitions to forwarding
Data and voice over native vlan no QOS and no 802.1p trunk
80% of the user traffic should stay in the VLAN

8. What is the STP blocking state?
Notifies upstream neighbors by sending multicasts on behalf of hosts at the interval of the max update rate parameter.
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
0000.0c07.acxx where xx is the group number as a 2-digit hex value
Can hear only BDPUs

9. What address does HSRP send hello packets to?
All nondesignated ports - but ok for all ports
224.0.0.2 (all routers)
1-enable AAA on switch - 2-define RADIUS servers - 3-define authentication method - 4-enable 802.1x on switch - 5-conf. 802.1x ports - 6-allow hosts
Weak key rotation

10. What does the standby HSRP router do?
Flash (class 3)
Only the standby monitors the hello messages from the active router
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
All nondesignated ports - but ok for all ports

11. What are the VRRP group and priority numbers?
Group (0-255) - priority (1-254 254 is highest - 100 default)
Host Standby Router protocol. Cisco proprietary. Switch is either active - standby - or listen
3 seconds. Holdtime =3 hellos + 1
Checks the source MAC in the header against the sender MAC in the ARP reply

12. How does IPT behave when the voice VLAN is in vlan-id mode?
An L2 switch can only forward frames best effort unless going across a trunk
Once the CCM gives them the parameters - they use RTP
Data goes over native vlan - voice goes over specified VLAN - voice QOS is 802.1p
Those that connect to other switches

13. What is a microcell?
0000.0c07.acxx where xx is the group number as a 2-digit hex value
Virtual Router Redundancy Protocol - pretty much the same as HSRP
By an ARP access list that defines the permitted bindings
When the size of a cell is intentionally reduced

14. RSTP uses which standard?
1- enable qos - 2-define qos parameters to be trusted - 3-make trust conditional - 4-instruct IP phone how to extnd boundary
802.1w
Group (0-1023) priority (1-255 higher better def 100)
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

15. What is the size of ISL encapsulation?
26-byte header - 4-byte trailer with CRC
They should be an unconditional Etherchannel because the WLC can't negotiate a channel.
A point to point port type but the neighboring device runs traditional 802.1D STP
Etherchannel ports have inconsistent config

16. What is NSF?
Per-port or globally for all fiber-optic ports. Can be enabled globally - but will only affect fiber ports
They shorten their bridge table aging times from default (300sec) to the fowarding delay (15 sec)
Nonstop forwarding is an interactive method focusing on rebuilding the RIB after SUP switchover
0-65535 (def 32768) lower=better

17. What is a direct topology change?
FE and GE
Packets must be sent to the L3 engine for further processing
Roughly 50%
One that can be detected on a switch interface (ie. Up/down)

18. How does HSRP plain text authentication work?
Real-time functions such as beacons and probes - encryption and interactions with the client at L2
Multicasts to 224.0.0.18 (VRRP)
A key string of up to 8 characters is sent. Default is cisco.
Cisco proprietary. 1 instance of STP/VLAN. Requires ISL instead of dot1q

19. What is a null adjacency?
By an ARP access list that defines the permitted bindings
1 per segment
The number of times the entry has been updated since the table was generated
Used to switch packets destined for the null interface

20. What is the default 10mbps Enet duplex?
Disabled - init - listen - speak - standby - active
The station can transmit immediately and wait for an ack
Half-duplex
The port uses 802.1x exchange to move from unauthorized to authorized. Requires app on client

21. What is the port number range?
0-255
A router keeps a routing table and an ARP table. The FIB combines them for every next-hop entry
All L2 connectivity should be contained within the access layer.
Data goes over native vlan - voice goes over VLAN0 - voice QOS is 802.1p

22. What is portfast?
Hosts associated with a secondary VLAN can communicate with ports on the primary but not with another secondary VLAN
802.11
Almost eliminates listening and learning states for single hosts on an access link
5 classes with 3 drop precedences

23. What does a LAP do if it loses communication with it's WLC?
Causes switch to actively determine whether alternative paths exist to root bridge in case ther eis an indirect failure
CEF is distributed across multiple L3 forwarding engines - typically on Catalyst 6500 line cards each having only a subset
Reboots and searches for a new WLC
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

24. What is DSCP codepoint EF(46)?
Hosts within a secondary can communicate with each other and with the primary - but not with another secondary vlan
Limits the number if dhcp requests on a port
The switch adds its MAC to the option 82 field so that the DHCP reply echoes back the switch's own information
Critical...used most often for IPT

25. Can ARP replies be checked
Yes
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
A MAC is seen on a different port
2 seconds (def)

26. What is DSCP codepoint AF21(18)?
3 seconds. Holdtime =3 hellos + 1
Immediate (class 2)
1- trunking mode - 2-trunk encapsulation - 3-native VLAN - 4-allowed VLAN
They must be carried over a voice VLAN (VVID) or over a regular data VLAN (ie. The native VLAN or the PVID)

27. What is the access layer best practice?
Switch(config-if)# standby xx where x= group number
Every hello interval regardless of whether BDPUs are received from root - allowing any switch to take an active role maintaining the topology
By brining up a tunnel between them to carry 802.11 related messages and client data.
All L2 connectivity should be contained within the access layer.

28. By default - what submode does PAgP operate in with the desirable and auto modes?
Silent
The master router can share the VIP
Only for the offending VLAN on the port
Used when ACLs specify port ranges...used by TCAM

29. How is an RSTP edge port configured
No
Connects with SONET or SDH
With portfast
Disabled - blocking - listening - learning - forwarding

30. What does UDLD do?
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
By configuring every switch port to have an expected and controlled behavior
19
Protects STP when a physical malfunction only allows traffic in 1 direction - even though the link shows as up (cisco proprietary)

31. What are the steps of RSTP convergence?
They are locally significant on an interface. HSRP1 on one VLAN is different from HSRP1 on another
By short-circuiting the max age timer
Auto mode
1- root bridge is elected - 2-the state of eery switch port in the STP domain must be brought from blocking state to the appropriate state

32. Where is UDLD enabled?
Dynamic arp inspection
It is enabled by default on all CEF capable switches
All fiber-optic links between switches (must be enabled on both ends)
Two distribution switches that aggregate one or more access switches

33. What does the switchport host macro do?
Only a single host connects . If one BDPU is received - it is no longer an edge port
Sets the switchport mode to access - enables portfast - and turns off channel grouping for the port
The TOS field in the header is used. 2 methods 3 bits or 6 bits
Manages addition - deletion and renaming VLANs across the network

34. How does HSRP election work?
Frames are forwarded
Access or trunk
1-lowest root bridge ID - 2-lowest root path cost - 3-lowest bridgeID - 4-lowest port ID
Based on priority (0-255). Default is 100. Highest IP is tie breaker

35. What 2 tunnelling mechanisms do the LAP and WLC use to communicate?
LWAPP (Cisco proprietary) and CAP-WAP (standards based)
Can hear only BDPUs
Distribution
Up to 4 can be used in a group. Called active virtual forwarders (AVF)

36. What is an ESS?
When the AP uplinks to an Ethernet network.
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
By an ARP access list that defines the permitted bindings
12 kbps with headers and compression

37. How is an instance defined?
By name - config revision - and instance to vlan mapping table
When a port moves into forwarding or from fowarding or learning to blocking.
If a proposal is received - the recipient isolates - all nonedge ports blocked until proposal sent causing neighbors to synch - which propagates out in waves
That they aren't using the same frequencies.

38. When looking at the sh spanning tree output - What does P2P peer(STP) denote?
A point to point port type but the neighboring device runs traditional 802.1D STP
Distributed coordinion function - the use of timers to prevent wireless collisions
Matching SSID - compatible data rate - authentication credentials
Show standby

39. How should the switch port to which a WLC be configured?
A router keeps a routing table and an ARP table. The FIB combines them for every next-hop entry
Trunk
Single instance of STP for all VLANs. BDPUs are sent over trunks using the native VLAN with untagged frames. Dot1q based
Gateway load balancing protocol - cisco proprietary

40. FE connectors use...
2 strand MMF with MT-RJ or SC connectors
Automatically using DTP and CDP
Data goes over native vlan - voice goes over specified VLAN - voice QOS is 802.1p
Port with best root path cost on segment

41. What types of link can an etherchannel be?
By default weight is 100. Can be made dynamic per interface
Access or trunk
Route processor redundancy - redundant sup is partially booted and initialized and must reload module in the switch and init all sup functions
Packets must be sent to the L3 engine for further processing

42. What is the portr ID?
Each physical interface has a different IP address. All physical interfaces point to a virtual interface called the standby address or VIP
Incoming frames dropped - but MACs learned
16 bits (8b port priority - 8b port number)
Data and voice over native vlan - no QOS but still uses 802.1p trunk

43. RSTP BPDU structure
Connects to a host on an isolated or community vlan. Communicates only with promiscuous port or ports on same community vlan
Time between BDPUs sent by root bridge. Default of 2 seconds
The ASIC
Some unused bits are used to allow a port to identify its role and state. Also the BDPUs state that they are V2 BDPUs

44. Can MSTP interoperate with 802.1q and/or PVST+?
1- trunking mode - 2-trunk encapsulation - 3-native VLAN - 4-allowed VLAN
Yes to both
Collision domain
19

45. What are the PAgP negotiation modes
Determines when the AVG will stop using the old VMAC in ARP replies
Change in trunk encap
Only a single host connects . If one BDPU is received - it is no longer an edge port
On (all ports channel) - auto (channels when asked) - and desirable(actively asks to form a channel)

46. What is route caching?

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47. How do you configure DAI for statically configured IP addresses?
By an ARP access list that defines the permitted bindings
Multicast to 01-80-c2-00-00-00
Port stays up - packets from violating MACs dropped - no logging
RPR - RPR+ - and SSO

48. What are the 3 trunk switchport modes?
Trunk - dynamic auto - dynamic desireable (default)
Forces the router to wait for a period of time before attempting overthrow
Packets are discarded due to an ACL or policy action
16 - IST gets MSTI 0 - 1-15 are available for use. MSTIs are locally significant to the MST region

49. What is the LACP priority range?
Root - designated - alternate - and backup
Feature Manager - after the ACL is created - the FM compiles the ACEs into the table
1-65535 (def 32768) lower priority - higher probability
Control functions

50. How much BW does a PSTN connection use?
They are locally significant on an interface. HSRP1 on one VLAN is different from HSRP1 on another
Any dhcp reply coming from an untrusted port is discarded and the offending port is put in errdisable
63 kbps
All ARP packets that arrive on untrusted ports are inspected.