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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 is an insignificant topology change?
A host port goes up or down
Trusted ports
Needs hardware upgrade over WEP - uses AES encryption
1-name the chain - 2-establish a key number - 3-create the key string - 4-apply the chain to the string

2. What is RPVST+?
Each physical interface has a different IP address. All physical interfaces point to a virtual interface called the standby address or VIP
An instance of RSTP running for each VLAN on the switch. Changing from PVST to RPVST+ is disruptive
Route once - switch many
Variation in delay

3. What is the port number range?
Port stays up - but packets from violating MACs are dropped. Switch logs violating packets
Multicasts to 224.0.0.18 (VRRP)
Source IP and MAC must match those addresses learned by DHCP snooping or a static entry
0-255

4. When a host is connected to a switchport - why aren't frame errors propagated?
Because each frame is checked
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
The active router. All other routers are in backup state

5. What is the portr ID?
The campus network's backbone
The point at which a switch decides to trust incoming Qos. Usually at boundary with ISP
Show standby
16 bits (8b port priority - 8b port number)

6. How does HSRP plain text authentication work?
Per-port or globally for all fiber-optic ports. Can be enabled globally - but will only affect fiber ports
4
Incoming frames dropped - but MACs learned
A key string of up to 8 characters is sent. Default is cisco.

7. How does an L2 switch do QOS?
The time that a port spends in both listening and learning states . Default 15 seconds
Frames that barely exceed 1518B or 1622B due to headers
An L2 switch can only forward frames best effort unless going across a trunk
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

8. What is DSCP?
Differentiated services code point
Real-time Transport Protocol
Port with best root path cost on segment
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

9. What is a null adjacency?
The number of STP instances needed ot support the desired topologies and whether to map a set of VLANs to each instance
Use the spanning-tree root macro
Used to switch packets destined for the null interface
Used when there are 1 or more VLANs mapped to a single STP instance

10. What does the SP do?
Completed dhcp bindings - mac addresses - IP addresses - etc.
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
Global config (vlan - vtp mode - and vtp domain) and VLAN DB mode commands. Global config is preferred because VLAN DB mode commands are legacy
Effectively stops STP on filtered ports

11. How do you enable CEF?
Critical...used most often for IPT
It is enabled by default on all CEF capable switches
5 (0-4 with 4 being the highest)
Up to 54Mbps - not cross-compatible - 12 to 23 clean channels - 5.8 Ghz

12. What functions does a LAP perform?
Real-time functions such as beacons and probes - encryption and interactions with the client at L2
Frames that barely exceed 1518B or 1622B due to headers
They shorten their bridge table aging times from default (300sec) to the fowarding delay (15 sec)
Access

13. what should you do if you expect a PAgP capable switch at the other end vs. a server or host?
Configure non-silent submode
CEF is distributed completely among multiple L3 forwarding engines.
Distribution layer
Determines when the AVG will stop using the old VMAC in ARP replies

14. What are the characteristics of the core layer
Very high L3 throughput - no access lists or port filtering - redundancy and resilience - advanced QoS
Yes to both
The same as a standby group in HSRP
The ASIC

15. What are the 5 steps to manualy configure STP?
5 classes with 3 drop precedences
The same as a standby group in HSRP
The number of STP instances needed ot support the desired topologies and whether to map a set of VLANs to each instance
1-ID link path costs - 2-ID roodt bridge - 3-select root port (1/switch) - 4-select designated port (1/segment) - 5-ID blocking port

16. What must be supported for port-based security to occur?
Compatible with 802.11b - up to 54Mbps in 12 data rates - 3 channels - 2.4Ghz
Per-port or globally for all fiber-optic ports. Can be enabled globally - but will only affect fiber ports
802.1x with EAP over LAN (EAPOL)
Disabled - init - listen - speak - standby - active

17. What are the gotchas for uplinkfast?

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18. How does a DHCP server send WLC addresses?
Option 43
A point to point port type but the neighboring device runs traditional 802.1D STP
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
On by default

19. can root guard and udld be used together?
Connects to a host on an isolated or community vlan. Communicates only with promiscuous port or ports on same community vlan
If any BDUP is received on a port - it puts the port into the errdisable state
Yes
LACP port priority

20. Can loop guard and udld be used together?
Each frame transmits its expected duration time
Round robin - weighted - or host-dependent
When a specific interface is tracked - HSRP reduces it's priority after a specified interval.
Yes

21. RSTP BPDU structure
When a wireless station transmits a frame - the receiving one must send an ack
The number of times the CEF table has bee flushed and regenerated as a whole
Some unused bits are used to allow a port to identify its role and state. Also the BDPUs state that they are V2 BDPUs
Cisco ILP and 802.3af

22. What happens when switches receive a configuration BDPU?
They shorten their bridge table aging times from default (300sec) to the fowarding delay (15 sec)
Backbonefast uses RLQ to determine if upstream switches have stable connections to root bridge
When each AP stands alone within the larger network.
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

23. What are the 2 UDLD modes?
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
Another router must have a higher HSRP priority and have preemt set up
VTP server for domain null with no password or secure mode
Normal and aggressive

24. What is the 80/20 rule?
80% of the user traffic should stay in the VLAN
Frames are forwarded
A router keeps a routing table and an ARP table. The FIB combines them for every next-hop entry
Normal and aggressive

25. What does the minimum keyword do in HSRP?
Round robin - weighted - or host-dependent
They must be carried over a voice VLAN (VVID) or over a regular data VLAN (ie. The native VLAN or the PVID)
Makes use of the DHCP snooping database and static ip source binding entries. If enabled - switch will test addresses
Forces the router to wait for a period of time before attempting overthrow

26. What does the standby HSRP router 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
Only the standby monitors the hello messages from the active router
Turn on port security
Root - designated - alternate - and backup

27. What are the PAgP negotiation modes
Yes
By using a trunk link
On (all ports channel) - auto (channels when asked) - and desirable(actively asks to form a channel)
FIB

28. What is DCF?
Root - designated - alternate - and backup
Interim solution - uses same hardware as WEP - but uses TKIP encryption
Distributed coordinion function - the use of timers to prevent wireless collisions
Receives the first packet of a traffic flow and routes it

29. RSTP learning state
0-255
By using an Ether-IP tunnel
802.1w
Incoming frames dropped - but MACs learned

30. What is the default network diameter?
Route processor redundancy - redundant sup is partially booted and initialized and must reload module in the switch and init all sup functions
Can hear only BDPUs
7 switches from root bridge
Only a single host connects . If one BDPU is received - it is no longer an edge port

31. What does the RP do?
Receives the first packet of a traffic flow and routes it
A client can roam to any WLC as long as it stays in a mobility group
Use sh interface on the interface and look for error counts > 10
If the client maintains the same IP address as it roams between Aps. All must have same VLAN - SSID - and subnet

32. What is the VRRP skew time?
Yes
Hold time is 3xhello. A skew time of 256ms-routerpriority)/256ms is added
A group of wireless devices that share a common SSID
The MST instance (MSTI) runs alongside the IST and represents an STP instance

33. What are the 5 steps a LAP uses to establish communication with a WLC?
Isolated and community
Full duplex
The same as a standby group in HSRP
1-LAP gets a DHCP address - 2-LAP learns IP of available WLC - 3-LAP sends a join request to WLC and receives join reply - 4-WLC sends code image - if necessary - 5-Tunnels are created

34. What feedback mechanism does wireless use?
Traffic types and patterns - amount of L3 switching cap. At dist. Layer - # users at access layer - geography - size of spanning tree domains
The point at which a switch decides to trust incoming Qos. Usually at boundary with ISP
When a wireless station transmits a frame - the receiving one must send an ack
One that can be detected on a switch interface (ie. Up/down)

35. What is the format of the VRRP virtual MAC?
L2
An L2 switch can only forward frames best effort unless going across a trunk
0000.5e00.01xx
Notifies upstream neighbors by sending multicasts on behalf of hosts at the interval of the max update rate parameter.

36. How do you show HSRP status
Show standby
2
By using a hash of a key string
Switch(config-if)# glbp xx where xx = group number

37. can root guard and loop guard be used together
The DCF interframe space- the random backoff time before a wireless set can transmit
Single instance of STP for all VLANs. BDPUs are sent over trunks using the native VLAN with untagged frames. Dot1q based
The active router. All other routers are in backup state
No

38. What is errdisable dtp-flap?
Time between BDPUs sent by root bridge. Default of 2 seconds
Change in trunk encap
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
Via an 802.1Q trunk or a single VLAN access port

39. What can cause a wireless client to switch between Aps?
An instance of RSTP running for each VLAN on the switch. Changing from PVST to RPVST+ is disruptive
Plain text or md5
Missed beacons - dropped packets (max retry) - weak signal (data rate switches down) - an AP periodicallytries to find a stronger signal
Configuration and TCN

40. RSTP root port
19
Port with best root path cost
Full duplex
Determines when the AVG will stop using the old VMAC in ARP replies

41. What is the switch block?
VTP server for domain null with no password or secure mode
1-name the chain - 2-establish a key number - 3-create the key string - 4-apply the chain to the string
Two distribution switches that aggregate one or more access switches
Root - designated - blocking - alternate - forwarding (host)

42. How does L3 QOS classification happen?
A group of wireless devices that share a common SSID
The TOS field in the header is used. 2 methods 3 bits or 6 bits
1-ID link path costs - 2-ID roodt bridge - 3-select root port (1/switch) - 4-select designated port (1/segment) - 5-ID blocking port
Local only

43. What is unique about HSRP group numbers?
They are locally significant on an interface. HSRP1 on one VLAN is different from HSRP1 on another
Data and voice over native vlan no QOS and no 802.1p trunk
Based on priority (0-255). Default is 100. Highest IP is tie breaker
Data goes over native vlan - voice goes over VLAN0 - voice QOS is 802.1p

44. What is an ESS?
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
Manually
When a wireless station transmits a frame - the receiving one must send an ack
When the AP uplinks to an Ethernet network.

45. What is best effort delivery QOS?
CEF is distributed completely among multiple L3 forwarding engines.
Dynamic arp inspection
No
Switches make an effort to move packets as quickly as possible

46. What is DSCP codepoint AF11(10)?
Port stays up - packets from violating MACs dropped - no logging
Priority (class 1)
The MST instance (MSTI) runs alongside the IST and represents an STP instance
Frames that barely exceed 1518B or 1622B due to headers

47. What is the range of PAgP channel group numbers?
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
300 sec by default
1 to 64
The switch adds its MAC to the option 82 field so that the DHCP reply echoes back the switch's own information

48. What are 2 ways to configure VLAN and VTP information?
Global config (vlan - vtp mode - and vtp domain) and VLAN DB mode commands. Global config is preferred because VLAN DB mode commands are legacy
Plain text or md5
The topology is pre-populated by downloading the topology DB into the FIB and dynamically updated. Called Cisco Express Forwarding
FE - GE - and aggregated FE/GE Etherchannels

49. What is a bridge ID made up of?
The distribution layer should have only L3 links
Bridge priority and MAC
Yes
Automatically negotiates a common trunk mode between switches

50. How do you configure DAI for statically configured IP addresses?
The station must wait until the frame in progress has completed - then wait a random amount of time before transmitting
Stateful switchover - redundant sup is fully booted and init'd. Both start and run config are synched as is L2 information - and switchinterfaces.
By an ARP access list that defines the permitted bindings
Port with best root path cost on segment