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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 does Root Guard do?
Controls where candidate root bridges can be connected and found on a network
Traffic types and patterns - amount of L3 switching cap. At dist. Layer - # users at access layer - geography - size of spanning tree domains
Normal and aggressive
First configure a L3 interface in same VLAN as clients - then use the ip helper-address command to ID the DHCP server

2. How should the switch port to which a LAP be configured?
Access
1 to 64
Makes use of the DHCP snooping database and static ip source binding entries. If enabled - switch will test addresses
Packets are discarded due to an ACL or policy action

3. What 2 conditions does IP source guard check for?
Differentiated services code point
Source IP and MAC must match those addresses learned by DHCP snooping or a static entry
Via an 802.1Q trunk or a single VLAN access port
Discarding - learning - forwarding

4. How does DSCP handle IP precedence?
5 classes with 3 drop precedences
Switches make an effort to move packets as quickly as possible
Switch(config-if)# vrrp xx where xx= group number
Used to switch packets that can't be forwarded normallly due to an encapsulation failure - unresolved address - unsupported protocol - etc.

5. What is RPVST+?
Reboots and searches for a new WLC
5 (0-4 with 4 being the highest)
0-255
An instance of RSTP running for each VLAN on the switch. Changing from PVST to RPVST+ is disruptive

6. What types of ports autonegotiate?
Round robin - weighted - or host-dependent
FE and GE
Feature Manager - after the ACL is created - the FM compiles the ACEs into the table
3 seconds. Holdtime =3 hellos + 1

7. How does RSTP converge?
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
If a proposal is received - the recipient isolates - all nonedge ports blocked until proposal sent causing neighbors to synch - which propagates out in waves
It updates the L2 headers with the proper src and dst MAC - L3 TTL - L3 checksum - and L2 checksum information
By name - config revision - and instance to vlan mapping table

8. How many designated ports are there?
Use sh interface on the interface and look for error counts > 10
1-lowest root bridge ID - 2-lowest root path cost - 3-lowest bridgeID - 4-lowest port ID
1 per segment
Sends special layer 2 UDLD frames and expects an echo. Both ends must be configured for UDLD

9. How does every VRRP command begin?
Yes
MST attributes must be manually entereed on each switch in the region. They don' t propagate like VTP.
When the size of a cell is intentionally reduced
Switch(config-if)# vrrp xx where xx= group number

10. How does an L2 switch do QOS?
By default weight is 100. Can be made dynamic per interface
An L2 switch can only forward frames best effort unless going across a trunk
When a wireless station transmits a frame - the receiving one must send an ack
It can't

11. Define VRRP
L2
Virtual Router Redundancy Protocol - pretty much the same as HSRP
Group (0-1023) priority (1-255 higher better def 100)
When the AP uplinks to an Ethernet network.

12. How do you implement MST?

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13. What are the 5 steps a LAP uses to establish communication with a WLC?
A point to point port type but the neighboring device runs traditional 802.1D STP
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
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
VTP server for domain null with no password or secure mode

14. Where are security and QoS ACLs stored?
The port uses 802.1x exchange to move from unauthorized to authorized. Requires app on client
TCAM
First configure a L3 interface in same VLAN as clients - then use the ip helper-address command to ID the DHCP server
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.

15. what if a secondary VLAN?
An AP's coverage area
Checks the destination MAC in the header against the target MAC in the ARP reply
They disguise the origin of an attack
Hosts associated with a secondary VLAN can communicate with ports on the primary but not with another secondary VLAN

16. What is accelerated CEF (aCEF)?
CEF is distributed across multiple L3 forwarding engines - typically on Catalyst 6500 line cards each having only a subset
Src-dst-ip
A VLAN that spans the entire fabric
Yes

17. What are the 3 trunk encap modes?
Used when there are 1 or more VLANs mapped to a single STP instance
Two distribution switches that aggregate one or more access switches
Isl - dot1q - negotiate (default)
Round robin - weighted - or host-dependent

18. What is the default FE duplex?
Full duplex
Switchpotrt nonegotiate
An AP's coverage area
The same as a standby group in HSRP

19. What does the SP do?
Connects to a host on an isolated or community vlan. Communicates only with promiscuous port or ports on same community vlan
Using digital certificates
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
Prevents the dhcp binding DB from being checked.

20. Where is loop guard enabled?
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.
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
1 second. Backup routers can learn the interval from the master
All nondesignated ports - but ok for all ports

21. What is a community secondary VLAN?
Show standby
After forwarding delay - port can learn new MAC addresses
Hosts within a secondary can communicate with each other and with the primary - but not with another secondary vlan
Usually QoS from VOIP but not PC dataa

22. How does HSRP do MD5 authentication?
Checks the sender's ip in all arp requests and checks the sender's IP against target IP in all replies
Makes use of the DHCP snooping database and static ip source binding entries. If enabled - switch will test addresses
When a specific interface is tracked - HSRP reduces it's priority after a specified interval.
By using a hash of a key string

23. What is the range of HSRP group numbers?
0-255
1/2 and 3/6
Matching SSID - compatible data rate - authentication credentials
When each AP stands alone within the larger network.

24. What is the STP hello timer?
Show standby
Time between BDPUs sent by root bridge. Default of 2 seconds
FE - GE - and aggregated FE/GE Etherchannels
L2

25. What are the 2 UDLD modes?
Normal and aggressive
Port with best root path cost
The campus network's backbone
Very high L3 throughput - no access lists or port filtering - redundancy and resilience - advanced QoS

26. What is the switch block?
Each network device handles packets individually with no advance reservations
Two distribution switches that aggregate one or more access switches
The time interval that a switch stores a DBPU before discarding it. Default 20 seconds
Used when there are 1 or more VLANs mapped to a single STP instance

27. What is DAI?
Roughly 50%
Using a mobility exchange message
2 strand MMF with MT-RJ or SC connectors
Dynamic arp inspection

28. How long are TCAM masks?
134 bits
The port is forced to always authorize any connected client with no authentication necessary (default)
Port with redundant - but less deisrable connection to a segment. Possibly root candidate
From the DHCP snooping database or from static entries

29. What feedback mechanism does wireless use?
To a VLAN and not to a VLAN interface (SVI)
Yes
When a wireless station transmits a frame - the receiving one must send an ack
16 bits (8b port priority - 8b port number)

30. What is the STP disabled state?
Admin down
Used when there are 1 or more VLANs mapped to a single STP instance
Prevents the dhcp binding DB from being checked.
Interim solution - uses same hardware as WEP - but uses TKIP encryption

31. What is a vlan?
Will trunk if asked
The time that a port spends in both listening and learning states . Default 15 seconds
A single broadcast domain
Host Standby Router protocol. Cisco proprietary. Switch is either active - standby - or listen

32. How do IP phones communicate with each other?
Between interfaces that are assigned to L2 VLANs or L2 trunks
900 MHz - 2.4Ghz - and 5-6GHz
CEF is distributed across multiple L3 forwarding engines - typically on Catalyst 6500 line cards each having only a subset
Once the CCM gives them the parameters - they use RTP

33. How does IPT behave when the voice VLAN is in untagged mode?
To a VLAN and not to a VLAN interface (SVI)
Via an 802.1Q trunk or a single VLAN access port
Data and voice over native vlan - no QOS but still uses 802.1p trunk
They should be an unconditional Etherchannel because the WLC can't negotiate a channel.

34. What is arp throttling?
Automatically using DTP and CDP
Makes use of the DHCP snooping database and static ip source binding entries. If enabled - switch will test addresses
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
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

35. What does BDPU filtering do?
Traffic types and patterns - amount of L3 switching cap. At dist. Layer - # users at access layer - geography - size of spanning tree domains
Effectively stops STP on filtered ports
1- enable qos - 2-define qos parameters to be trusted - 3-make trust conditional - 4-instruct IP phone how to extnd boundary
Time between BDPUs sent by root bridge. Default of 2 seconds

36. How do you find duplex mismatches?
The RP listens to a flow's 1st packet for the dest. The SE listens to the packet and dest and puts a shortcut in the MSL cache. Netflow switching - route once - switch many
Any dhcp reply coming from an untrusted port is discarded and the offending port is put in errdisable
Use sh interface on the interface and look for error counts > 10
Because each frame is checked

37. Can ARP replies be checked
Port with redundant - but less deisrable connection to a segment. Possibly root candidate
Immediate (class 2)
Yes
The frame tag contains a 3 but portion tagged from 0 (low) to 7 (high)

38. What is DSCP?
Feature Manager - after the ACL is created - the FM compiles the ACEs into the table
Differentiated services code point
It updates the L2 headers with the proper src and dst MAC - L3 TTL - L3 checksum - and L2 checksum information
Route once - switch many

39. What is the STP learning state?
Makes use of the DHCP snooping database and static ip source binding entries. If enabled - switch will test addresses
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
After forwarding delay - port can learn new MAC addresses
A client can roam to any WLC as long as it stays in a mobility group

40. What is an SVI?
After forwarding delay - port can learn new MAC addresses
Used when there are 1 or more VLANs mapped to a single STP instance
Group (0-255) - priority (1-254 254 is highest - 100 default)
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

41. FE connectors use...
Yes
Between any type of interface as long as the interface can have an L3 address assigned
1- trunking mode - 2-trunk encapsulation - 3-native VLAN - 4-allowed VLAN
2 strand MMF with MT-RJ or SC connectors

42. What does port-security restrict do?
Half-duplex
63 kbps
Port stays up - but packets from violating MACs are dropped. Switch logs violating packets
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

43. What is the access layer best practice?
All L2 connectivity should be contained within the access layer.
To the virtual port-channel interface
1-lowest root bridge ID - 2-lowest root path cost - 3-lowest bridgeID - 4-lowest port ID
The switch adds its MAC to the option 82 field so that the DHCP reply echoes back the switch's own information

44. RSTP BPDU structure
1/2 and 3/6
LACP port priority
Weak key rotation
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 method of QOS does voice traffic use most frequently?
Gateway load balancing protocol - cisco proprietary
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.
2
Differentiated services

46. What is the SDM?
Checks the destination MAC in the header against the target MAC in the ARP reply
Switching Database Manager - configures and prunes TCAM partitions
By creating a static IP binding
1-client sends DHCP discover as broadcast - 2-DHCP server sends DHCP offer - client sends DHCP Request - DHCP server sends DHCP ack

47. How does PAgP form etherchannels?
It is enabled by default on all CEF capable switches
The station must wait until the frame in progress has completed - then wait a random amount of time before transmitting
Only on ports that have same static VLANs or trunking. It also modifies parameters of the channel if one of the ports is modified
A point to point port type

48. where does L2 switching occur?
Between interfaces that are assigned to L2 VLANs or L2 trunks
Receives the first packet of a traffic flow and routes it
Port with alternative path to root less desirable than root
First configure a L3 interface in same VLAN as clients - then use the ip helper-address command to ID the DHCP server

49. What is the portr ID?
0007.b4xx.xxyy where xx.xx is six 0 bits followed by a 10-bit GLBP group numberr. Yyyy is the virtual forwarder number
Variation in delay
16 bits (8b port priority - 8b port number)
As a VLAN access map

50. What is dynamic desireable?
Limits the number if dhcp requests on a port
Src-ip - dst-ip - src-dst-ip - src-mac - dst-mac - src-dst-mac - src-port - dst-port - src-dst-port
One that can be detected on a switch interface (ie. Up/down)
The port asks the other end to trunk