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CCIE R&S - LAN Swt
CCIE R&S - Written - LAN Switching
| Question | Answer |
|---|---|
| 3 Unicast Flooding Causes | Asymmetric Routing, STP Topology Changes, MAC Table Overflow |
| 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 |
| 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. |
| 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 |
| What is another name for STP System ID Extension? | MAC address reduction |
| How is priority adjusted to accommodate VLAN ID? | In increments of 4096 |
| What is the default priority? | 32768 |
| Two ways to set priority? | With a macro (primary or secondary) or direct numeric value |
| How can STP parameters be set for all VLANs? | By leaving off the 'VLAN' parameter in the command |
| What is the default STP Hello Timer? | 2 seconds |
| Each switch updates these 4 fields in the Hello before forwarding. | Cost, Bridge ID, Port Priority, Port Number |
| Every port on the root bridge is a __________. | designated port |
| 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 |
| 5 STP Port States in order of occurrence | Disabled, Block, Listening, Learning, Forwarding |
| 802.1d blocking timer, name and length? | max-age, 10 times hello timer |
| 802.1d listening timer name and length? | forward delay, 15 seconds |
| 802.1d learning timer name and length | forward delay, 15 seconds |
| 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 |
| 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 |
| 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 |
| 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 |
| In 802.1d, how does port fast speed convergence? | It ignores the listening and learning states on the ports |
| 802.1d enhancement for access layer switches | UplinkFast |
| 802.1d enhancement for entire topology | BackboneFast |
| 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 |
| In 802.1d, what is the purpose of a RLQ? | To see if the neighboring switch is still receiving Hellos from the root |
| 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 |
| IN 802.1d, what does the BackboneFast requesting switch do once it learns of the indirect link failure? | Skip max-age timer and converge |
| What will UplinkFast manipulate for redundancy | Bridge priority value to 49,152, and all ports costs to 3,000 |
| What does UplinkFast track? | Alternate root ports |
| 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 |
| Lowest possible Root Bridge ID | 0 |
| Recommended bridge priority for backup root | 8192 |
| UplinkFast default priority | 49152 |
| Default STP Extended System ID | 4107 |
| 3 Port States of 802.1w | Discarding, Learning, and Forwarding |
| 4 Port Roles of 802.1w | Root Port, Designated Port, Alternate Port, Backup Port |
| 802.1w Alternate Port is backup to what? | Root Port |
| 802.1w Backup Port is backup to what? | Designated port |
| 802.1w replaces simple use of timers with what? | Proposal and Agreement process |
| In 802.1w, what is the 'max-age' equivalent timer? | 3 times the hello timer |
| 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 |
| In 802.1w, how are edge ports different from point-to-point ports? | TCNs are not sent when edge ports go down |
| 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 |
| In 802.1w, what are the three types of links? | Point-to-point, shared, and edge |
| What is the default instance for MST? | 0 |
| 3 important steps for 802.s configuration | Region Name, Revision Number, VLAN to Instance Mappings |
| In 802.1s, how can all ports be used? | Some ports block for one VLAN, while forwarding for another |
| 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 |
| What is true of QoS configurations in an ether-channel setup? | It must match on all physical ports, not configured on logical interface |
| What 8 things can a port-channel interface load-balance on? | source and destination mac or ip address, tcp and udp ports |
| What 5 port items have to be identical for PortChannel? | Speed, Duplex, Access VLAN Info, Trunk info, STP cost on all links per switch |
| How does UDLD detect a uni-directional link? | Layer 2 messaging |
| 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) |
| This STP Protection Mechanism prevents against hardware or software failures | LoopGuard |
| This STP Protection Mechanism prevents against fiber optic problems | UDLD |
| This STP Prevention mechanism enforces the STP domain borders and keeps the active topology predictable | BPDUGuard |
| This STP Prevention mechanism enforces the Layer 2 STP topology | RootGuard |
| This STP Prevention mechanism stops BPDUs from being sent on a port and also ignores received BPDUs | BPDUFilter |
| This L2 prevention mechanism monitors traffic by traffic type in 1 second intervals | Storm Control |
| What is the size of ISL encapsulation? | 26-byte header, 4-byte CRC trailer |
| What does ISL use for source address in the header? | source address of trunking device |
| What multicast MAC destinations are used in ISL? | 0100.0C00.0000 or 0300.0C00.0000 |
| What is the size of dot1q encapsulation? | 4-byte header after the source address |
| What spanning-tree does 802.1q support on non-Cisco switches? | Common Spanning Tree (CST) |
| When 802.1Q operates with CST, what tunnel MAC address destination is used? | 0100.0CCC.CCCD |
| Which trunk modes don't send DTP frames? | off, auto, nonegotiate |
| Which trunk modes send DTP frames? | on, desirable |
| 3 modes of VTP? | Server, Client, Transparent |
| This VTP mode only learns its database from server | Client |
| This VTP mode is the default | Server |
| This VTP mode ignores, but forwards messages | Transparent |
| 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 |
| What VLANs can be advertised in VTP versions 1 and 2? | Normal-range (1-1005) |
| What VTP credential can prevent trunk formation? | VTP domain |
| What is the size of the PPP header? | 8 bytes |
| What are the cabling pin matchings for a straight-through cable? | 1-1, 2-2, 3-3, 6-6 |
| What are the cabling pin matchings for a cross-over cable? | 1-3; 2-6; 3-1; 6-2 |
| What pins do PC NIC cards transmit and receive on? | Tx 1,2; Rx 3,6 |
| What pins do switch ports transmit and receive on? | Tx 3,6; Rx 1,2 |
| What is the assumed duplex for un-negotiated 10M, 100M, and 1000M links? | 10M, 100M - half, 1000M - full |
| What is HDX loopback circuitry? | NIC sends Tx signal to the Rx side. If another device is sending, it will detect the overlapping signals |
| What is 802.3u? | FastEthernet (copper and optical) |
| What is 802.3z? | GigabitEthernet over optical |
| What is 803.ab | GigabitEthernet over copper |
| 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 |
| This MAC address code is in the first 3 bytes? | Organization Unique Identifier (OUI) |
| What is canonical or little-endian bit significance? | In each byte, the left most bit is least significant |
| 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 |
| 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 |
| What is the ARP EtherType? | 0x0806 |
| When does traffic modification take place in Rx SPAN? | No traffic modified |
| When does traffic modification take place in Tx SPAN? | Before frames are sent |
| In SPAN, if the 'encapsulation replicate' command is types, what other frames are forwarded? | CDP, STP BPDUs, VTP, DTP, PagP |
| What are the valid session numbers in SPAN? | 1 to 66 |
| What percent of errors are acceptable when running in half-duplex mode? | 1 to 2% |
| What types of errors are expected in Half Duplex mode? | FCS, Alignment, Runts, and Collisions |
| 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) |
Created by:
ajballer15
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