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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. If there are 2 ports with same root cost - how is the tie broken for designated port?
Yes to both
1-lowest root bridge ID - 2-lowest root path cost - 3-lowest bridgeID - 4-lowest port ID
On ports where you never expect to find a root bridge for a VLAN
All user ports that have portfast enabled

2. What does the src-mac option do when checking ARP replies
The wireless clients communicate directly with no other means of connectivity such as a WAP
Checks the source MAC in the header against the sender MAC in the ARP reply
That they aren't using the same frequencies.
Usually QoS from VOIP but not PC dataa

3. How does loop guard block ports?
Only for the offending VLAN on the port
Port
The point at which a switch decides to trust incoming Qos. Usually at boundary with ISP
1 -2 -5.5 and 11 Mbps - Channels 1/6/11 - 2.4Ghz

4. What is a proxy arp?

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5. How does every VRRP command begin?
Disabled - init - listen - speak - standby - active
Switch(config-if)# vrrp xx where xx= group number
Data goes over native vlan - voice goes over specified VLAN - voice QOS is 802.1p
Globally

6. What is the STP forward delay timer?
Globally
The switch adds its MAC to the option 82 field so that the DHCP reply echoes back the switch's own information
The ASIC
The time that a port spends in both listening and learning states . Default 15 seconds

7. What must the other end be set to if PAgP desirable or LACP active mode is selected?
Port stays up - packets from violating MACs dropped - no logging
Either desirable or auto mode
Some unused bits are used to allow a port to identify its role and state. Also the BDPUs state that they are V2 BDPUs
Globally

8. What is a baby giant frame?
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
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
Port stays up - packets from violating MACs dropped - no logging

9. Does VTP pass private VLAN configuration?
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
Bridge priority and MAC
The configureable UDLD interval must be less than max age plus two intervals of forward delay
No

10. How does L3 QOS classification happen?
Incoming frames are dropped (combination of disabled - blocking - and listening)
Only on ports that have same static VLANs or trunking. It also modifies parameters of the channel if one of the ports is modified
The TOS field in the header is used. 2 methods 3 bits or 6 bits
The ASIC

11. What does the switchport host macro 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
They should be an unconditional Etherchannel because the WLC can't negotiate a channel.
Sets the switchport mode to access - enables portfast - and turns off channel grouping for the port
As a VLAN access map

12. What are the PAgP negotiation modes
The port asks the other end to trunk
A router keeps a routing table and an ARP table. The FIB combines them for every next-hop entry
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)

13. What are the steps to configure a PAgP port channel?
1-(opt) configure load balancing - 2-select the interface(s) - 3-assign the protocol - 4-select the mode and submode
Each network device handles packets individually with no advance reservations
Hold time is 3xhello. A skew time of 256ms-routerpriority)/256ms is added
With portfast

14. What does the reload keyword do in HSRP?
Yes
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
Forces the router to wait for a period of time after the switch is reloaded before attempting to overthrow
A TCN BDPU is sent out of the switch's root port. The switch will continue sending TCN's every hello interval until ack'd by upstream neighbor. The root bridge will send a Config BDPU to all switches

15. How can you load-balance with HSRP?
Create 2 hsrp groups - each with the active router being different switches - then have clients point to each
It can't
On root - because the root bridge propagates timers with config BDPU
A point to point port type but the neighboring device runs traditional 802.1D STP

16. What is SSO?

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17. What happens when the topology changes?

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18. Where shoul dmultilayer switches be implemented?
By sending a gratuitous ARP
Using a single WAP to centralize access and control over a group of wireless devices.
MST attributes must be manually entereed on each switch in the region. They don' t propagate like VTP.
Distribution layer

19. What are the 3 trunk encap modes?
Isl - dot1q - negotiate (default)
VTP server for domain null with no password or secure mode
Via an 802.1Q trunk or a single VLAN access port
An instance of RSTP running for each VLAN on the switch. Changing from PVST to RPVST+ is disruptive

20. What are the 2 choices for VLANs with IPT?
Per-port or globally for all fiber-optic ports. Can be enabled globally - but will only affect fiber ports
They must be carried over a voice VLAN (VVID) or over a regular data VLAN (ie. The native VLAN or the PVID)
Collision domain
The campus network's backbone

21. What are the 5 STP port roles?
Root - designated - blocking - alternate - forwarding (host)
RPR - RPR+ - and SSO
A MAC is seen on a different port
Roughly 50%

22. What types of link can an etherchannel be?
Completed dhcp bindings - mac addresses - IP addresses - etc.
7 switches from root bridge
Access or trunk
Group (0-255) - priority (1-254 254 is highest - 100 default)

23. How can BDPU Guard be configured?
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
Can send and receive BDPUs
If a proposal is received - the recipient isolates - all nonedge ports blocked until proposal sent causing neighbors to synch - which propagates out in waves
Globally or per-port

24. How does IPT behave when the voice VLAN is in untagged mode?
It is enabled by default on all CEF capable switches
Change in trunk encap
802.1D
Data and voice over native vlan - no QOS but still uses 802.1p trunk

25. What is UDLD aggressive mode?

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26. How far chould a VLAN extend?
Per VLAN
Distribution layer
Globally
Sends special layer 2 UDLD frames and expects an echo. Both ends must be configured for UDLD

27. What routing protocols support NSF?
Single instance of STP for all VLANs. BDPUs are sent over trunks using the native VLAN with untagged frames. Dot1q based
A path is pre-arranged for priority along the complete path from source to destination using the RSVP protocol.
PAgP (Cisco proprietary) and LACP (standards-based)
BGP - EIGRP - OSPF - and IS-IS.

28. What can cause a wireless client to switch between Aps?
An ac adaptor that plugs into a wall outlet.
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
Backbonefast uses RLQ to determine if upstream switches have stable connections to root bridge
Missed beacons - dropped packets (max retry) - weak signal (data rate switches down) - an AP periodicallytries to find a stronger signal

29. In a converged fabric - which switch(es) send config BDPUs?
Per VLAN
Root
Manages addition - deletion and renaming VLANs across the network
2 - one for control messages and one for data

30. What is a bridge ID made up of?
Any ports associated with an isolated vlan can reach the primary - but not any other secondary. Hosts withn an isolated vlan can't reach each other
Globally
Makes use of the DHCP snooping database and static ip source binding entries. If enabled - switch will test addresses
Bridge priority and MAC

31. What is DSCP codepoint AF41(34)?
2 seconds (def)
The same as a standby group in HSRP
No because they only participate if asked
Flash override (class 4)

32. What is the STP blocking state?
Only when a nonedge port transitions to forwarding
Single instance of STP for all VLANs. BDPUs are sent over trunks using the native VLAN with untagged frames. Dot1q based
Interim solution - uses same hardware as WEP - but uses TKIP encryption
Can hear only BDPUs

33. What is DSCP codepoint EF(46)?
By sending a gratuitous ARP
Critical...used most often for IPT
On root - because the root bridge propagates timers with config BDPU
Hosts associated with a secondary VLAN can communicate with ports on the primary but not with another secondary VLAN

34. What does BDPU filtering do?
Missed beacons - dropped packets (max retry) - weak signal (data rate switches down) - an AP periodicallytries to find a stronger signal
1-(opt) configure load balancing - 2-select the interface(s) - 3-assign the protocol - 4-select the mode and submode
Effectively stops STP on filtered ports
Full duplex

35. What does MSTP do?
Arp for local subnet - if on different subnet - will arp for dgw
Per-port or globally for all fiber-optic ports. Can be enabled globally - but will only affect fiber ports
Used when there are 1 or more VLANs mapped to a single STP instance
Multicast to 01-80-c2-00-00-00

36. What is DSCP codepoint AF31(26)?
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
If a proposal is received - the recipient isolates - all nonedge ports blocked until proposal sent causing neighbors to synch - which propagates out in waves
Flash (class 3)
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

37. What is the port priority range?
Use sh interface on the interface and look for error counts > 10
0-255 (lower is better)
Automatically negotiates a common trunk mode between switches
5 classes with 3 drop precedences

38. How are frames forwarded across a specific link?
From the DHCP snooping database or from static entries
Missed beacons - dropped packets (max retry) - weak signal (data rate switches down) - an AP periodicallytries to find a stronger signal
Configuration and TCN
Hashing algorithm

39. What is dhcp snooping rate limiting?
Differentiated services code point
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
The configureable UDLD interval must be less than max age plus two intervals of forward delay
Limits the number if dhcp requests on a port

40. What does the static keyword do when applying an arp ACL?
Some unused bits are used to allow a port to identify its role and state. Also the BDPUs state that they are V2 BDPUs
Prevents the dhcp binding DB from being checked.
When each AP stands alone within the larger network.
26-byte header - 4-byte trailer with CRC

41. What must be supported for port-based security to occur?
1- trunking mode - 2-trunk encapsulation - 3-native VLAN - 4-allowed VLAN
802.1x with EAP over LAN (EAPOL)
1-client sends DHCP discover as broadcast - 2-DHCP server sends DHCP offer - client sends DHCP Request - DHCP server sends DHCP ack
Hashing algorithm

42. What does port-security protect do?
All L2 connectivity should be contained within the access layer.
Checks the destination MAC in the header against the target MAC in the ARP reply
Port stays up - packets from violating MACs dropped - no logging
All non-edge ports are discarding. After the root bridge is identified - the port with superior BDPU becomes root

43. What are the port channel load balancing methods?
Real-time functions such as beacons and probes - encryption and interactions with the client at L2
Src-ip - dst-ip - src-dst-ip - src-mac - dst-mac - src-dst-mac - src-port - dst-port - src-dst-port
The active router. All other routers are in backup state
Nonstop forwarding is an interactive method focusing on rebuilding the RIB after SUP switchover

44. What is a service set?
1-client sends DHCP discover as broadcast - 2-DHCP server sends DHCP offer - client sends DHCP Request - DHCP server sends DHCP ack
4
A group of wireless devices that share a common SSID
Switchpotrt nonegotiate

45. What does the SP do?
The ASIC
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
5 classes with 3 drop precedences
Port with redundant - but less deisrable connection to a segment. Possibly root candidate

46. What is 802.1x force-authorized?
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
The port is forced to always authorize any connected client with no authentication necessary (default)
A private VLAN can be logically associated with a special secondary vlan
LACP port priority

47. What is a punt adjacency?
Packets must be sent to the L3 engine for further processing
After another forwarding delay - the port can send and receive data frames - collect MAC addresses - and send and receove BDPUs
The switch checks the MAC and IP reported in the reply against trusted values. If they don't match - it is dropped and logged
MST attributes must be manually entereed on each switch in the region. They don' t propagate like VTP.

48. If a wireless station needs to transmit and another device is transmitting - what happens?
PAgP (Cisco proprietary) and LACP (standards-based)
The number of STP instances needed ot support the desired topologies and whether to map a set of VLANs to each instance
All ports where root isn't expected
The station must wait until the frame in progress has completed - then wait a random amount of time before transmitting

49. What are the three basic types of QOS?
After another forwarding delay - the port can send and receive data frames - collect MAC addresses - and send and receove BDPUs
An instance of RSTP running for each VLAN on the switch. Changing from PVST to RPVST+ is disruptive
Use the spanning-tree root macro
Best effort delivery - integrated services model - and differentiated services model

50. RSTP BPDU structure
Some unused bits are used to allow a port to identify its role and state. Also the BDPUs state that they are V2 BDPUs
16 - IST gets MSTI 0 - 1-15 are available for use. MSTIs are locally significant to the MST region
Automatically using DTP and CDP
Root