CCIE R&S - Written - LAN Switching
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| 3 Unicast Flooding Causes | Asymmetric Routing, STP Topology Changes, MAC Table Overflow
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| 4 Steps of 802.1D Election Process | Elect the root bridge, Select root ports on all non-root bridges, Select designated ports per link, Block all other ports
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| How is the root bridge elected? | All switches begin forwarding Hellos out all ports claiming to be root. If a switch receives a superior Hello, it stops origination and forwards the superiors until only one switch is claiming to be root.
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| What does the Bridge ID consist of? | 2 Byte Priority, 6 Byte Mac Address, VLAN ID mapped to 12 lower order bits of Priority field
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| What is another name for STP System ID Extension? | MAC address reduction
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| How is priority adjusted to accommodate VLAN ID? | In increments of 4096
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| What is the default priority? | 32768
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| Two ways to set priority? | With a macro (primary or secondary) or direct numeric value
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| How can STP parameters be set for all VLANs? | By leaving off the 'VLAN' parameter in the command
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| What is the default STP Hello Timer? | 2 seconds
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| Each switch updates these 4 fields in the Hello before forwarding. | Cost, Bridge ID, Port Priority, Port Number
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| Every port on the root bridge is a __________. | designated port
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| What are the 3 steps of the STP tiebreaking process on a designated port? | Lowest path cost to root bridge, lowest sender Bridge ID, Lowest Port ID
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| 5 STP Port States in order of occurrence | Disabled, Block, Listening, Learning, Forwarding
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| 802.1d blocking timer, name and length? | max-age, 10 times hello timer
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| 802.1d listening timer name and length? | forward delay, 15 seconds
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| 802.1d learning timer name and length | forward delay, 15 seconds
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| In 802.1d, what does a non-root switch do when there is a STP port change? | Sends TCN BPDU out its root port every hello timer until acknowledged
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| In 802.1d, what two actions are taken by a non-root switch receiving a TCN from downstream switch? | Responds to downstream switch with the next hello BPDU with the Topology Change Acknowledgment (TCA) bit set, sends TCN BPDU out root port
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| In 802.1d, what does the root switch do when it receives the TCN BPDU? | Sets TC flag on next several hellos that are forwarded to all non-root switches
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| In 802.1d, what does a non-root switch do when it receives the hell o with the TC flag set? | Use forward delay timer to time out CAM entries
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| In 802.1d, how does port fast speed convergence? | It ignores the listening and learning states on the ports
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| 802.1d enhancement for access layer switches | UplinkFast
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| 802.1d enhancement for entire topology | BackboneFast
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| In 802.1d when a BackboneFast switch misses a hello, what action will it take? | It sends out a Root Link Query (RLQ) BPDU out the port on which the Hello should have arrived
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| In 802.1d, what is the purpose of a RLQ? | To see if the neighboring switch is still receiving Hellos from the root
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| In 802.1d, if a BackboneFast switch has a direct link failure, how would it respond to the received RLQ? | It would respond with a RLQ saying that the root path is lost
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| IN 802.1d, what does the BackboneFast requesting switch do once it learns of the indirect link failure? | Skip max-age timer and converge
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| What will UplinkFast manipulate for redundancy | Bridge priority value to 49,152, and all ports costs to 3,000
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| What does UplinkFast track? | Alternate root ports
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| What three things does an UplinkFast switch do when a failure occurs? | Immediately puts backup link in forwarding state, Sends one multicast frame per local MAC address as the source MAC, clear out its own CAM table
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| Lowest possible Root Bridge ID | 0
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| Recommended bridge priority for backup root | 8192
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| UplinkFast default priority | 49152
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| Default STP Extended System ID | 4107
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| 3 Port States of 802.1w | Discarding, Learning, and Forwarding
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| 4 Port Roles of 802.1w | Root Port, Designated Port, Alternate Port, Backup Port
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| 802.1w Alternate Port is backup to what? | Root Port
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| 802.1w Backup Port is backup to what? | Designated port
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| 802.1w replaces simple use of timers with what? | Proposal and Agreement process
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| In 802.1w, what is the 'max-age' equivalent timer? | 3 times the hello timer
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| How are BPDUs different in 802.1w? | It carries more information, like standard version of Cisco's 'RLQ' and is also used as a keepalive mechanism
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| In 802.1w, how are edge ports different from point-to-point ports? | TCNs are not sent when edge ports go down
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| How is the origin of TCNs different in 802.1w than 802.1d? | TCNs are originated on the bridge where the change occurs as opposed to just from the root bridge
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| In 802.1w, what are the three types of links? | Point-to-point, shared, and edge
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| What is the default instance for MST? | 0
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| 3 important steps for 802.s configuration | Region Name, Revision Number, VLAN to Instance Mappings
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| In 802.1s, how can all ports be used? | Some ports block for one VLAN, while forwarding for another
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| When connected an MST region to a non-MST region, how are loops prevented? | Internal Spanning Tree (IST), entire MST region appears to be one switch
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| What is true of QoS configurations in an ether-channel setup? | It must match on all physical ports, not configured on logical interface
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| What 8 things can a port-channel interface load-balance on? | source and destination mac or ip address, tcp and udp ports
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| What 5 port items have to be identical for PortChannel? | Speed, Duplex, Access VLAN Info, Trunk info, STP cost on all links per switch
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| How does UDLD detect a uni-directional link? | Layer 2 messaging
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| What are the 2 modes of UDLD and what actions do they take? | Aggressive (attempts to reconnect 8 times and err-disables if unsuccessfully), Enable (falls into loop-inconsistent state)
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| This STP Protection Mechanism prevents against hardware or software failures | LoopGuard
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| This STP Protection Mechanism prevents against fiber optic problems | UDLD
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| This STP Prevention mechanism enforces the STP domain borders and keeps the active topology predictable | BPDUGuard
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| This STP Prevention mechanism enforces the Layer 2 STP topology | RootGuard
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| This STP Prevention mechanism stops BPDUs from being sent on a port and also ignores received BPDUs | BPDUFilter
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| This L2 prevention mechanism monitors traffic by traffic type in 1 second intervals | Storm Control
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| What is the size of ISL encapsulation? | 26-byte header, 4-byte CRC trailer
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| What does ISL use for source address in the header? | source address of trunking device
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| What multicast MAC destinations are used in ISL? | 0100.0C00.0000 or 0300.0C00.0000
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| What is the size of dot1q encapsulation? | 4-byte header after the source address
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| What spanning-tree does 802.1q support on non-Cisco switches? | Common Spanning Tree (CST)
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| When 802.1Q operates with CST, what tunnel MAC address destination is used? | 0100.0CCC.CCCD
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| Which trunk modes don't send DTP frames? | off, auto, nonegotiate
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| Which trunk modes send DTP frames? | on, desirable
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| 3 modes of VTP? | Server, Client, Transparent
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| This VTP mode only learns its database from server | Client
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| This VTP mode is the default | Server
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| This VTP mode ignores, but forwards messages | Transparent
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| How will a VTP server or client behave if no VTP domain is configured? | It will assume the domain of the first received VTP update
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| What VLANs can be advertised in VTP versions 1 and 2? | Normal-range (1-1005)
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| What VTP credential can prevent trunk formation? | VTP domain
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| What is the size of the PPP header? | 8 bytes
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| What are the cabling pin matchings for a straight-through cable? | 1-1, 2-2, 3-3, 6-6
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| What are the cabling pin matchings for a cross-over cable? | 1-3; 2-6; 3-1; 6-2
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| What pins do PC NIC cards transmit and receive on? | Tx 1,2; Rx 3,6
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| What pins do switch ports transmit and receive on? | Tx 3,6; Rx 1,2
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| What is the assumed duplex for un-negotiated 10M, 100M, and 1000M links? | 10M, 100M - half, 1000M - full
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| What is HDX loopback circuitry? | NIC sends Tx signal to the Rx side. If another device is sending, it will detect the overlapping signals
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| What is 802.3u? | FastEthernet (copper and optical)
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| What is 802.3z? | GigabitEthernet over optical
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| What is 803.ab | GigabitEthernet over copper
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| What can a link that has one side HDX and one side FDX cause? | Occasional connection failures due to duplicate packets received on FDX side
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| This MAC address code is in the first 3 bytes? | Organization Unique Identifier (OUI)
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| What is canonical or little-endian bit significance? | In each byte, the left most bit is least significant
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| In MAC addresses, which bit is the Individual/Group (I/G) bit? Explain the bit settings. | Most significant bit of most significant byte; 0 = unicast, 1 = broadcast or multicast
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| In MAC addresses, which bit is the Universal/Local (U/L) bit? Explain the bit settings. | 2nd most significant bit of most significant bye; 0 = vendor assigned, 1 = administratively assigned
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| What is the ARP EtherType? | 0x0806
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| When does traffic modification take place in Rx SPAN? | No traffic modified
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| When does traffic modification take place in Tx SPAN? | Before frames are sent
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| In SPAN, if the 'encapsulation replicate' command is types, what other frames are forwarded? | CDP, STP BPDUs, VTP, DTP, PagP
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| What are the valid session numbers in SPAN? | 1 to 66
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| What percent of errors are acceptable when running in half-duplex mode? | 1 to 2%
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| What types of errors are expected in Half Duplex mode? | FCS, Alignment, Runts, and Collisions
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| What are the three types of Switch Internal Processing Methods? | Store-and-Forward (waits for entire frame), Cut-through (waits for destination address), Fragment-free (waits for first 64 bytes)
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