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27 Cards in this Set
- Front
- Back
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What are the three steps in spanning tree forwarding logic? |
STEP 1: Determine the vlan in which the frame should be forwarded
STEP 2: Add the source MAC address to the MAC address table STEP 3: Look for the destination MAC address of the frame in MAC address table, but only for entries in the VLAN identified at Step 1. (Odom, 2013 p.17) |
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What are the three classes of problems caused by not using STP in redundant LANs?
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1. Broadcast Storms
2. MAC Table Instability 3. Multiple Frame Transmission (Odom, 2013 p.24) |
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Define Broadcast Storms caused by not using STP in redundant LANs? |
The forwarding of a frame repeatedly on the same links consuming significant parts of the links capacities.
(Odom, 2013 p.24) |
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Define Mac Table Instability caused by not using STP in redundant LANs?
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The continual updating of a switch's MAC address table with incorrect entries, in reaction to looping frames, resulting in frames being sent to the wrong locations
(Odom, 2013 p.24) |
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Define Multiple Frame Transmission caused by not using STP in redundant LANs? |
A side effect of looping frames in which multiple copies of one frame are delivered to the intended host, confusing the host.
(Odom, 2013 p.24) |
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What are the four for forwarding or blocking in STP.
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1. All the root switch's ports
2. Each nonroot switch's root port 3. Each LANs designated port 4. All other working ports (Odom, 2013 p.26) (Odom, 2013 p.26) |
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CHARACTERIZATION of PORT |
STP STATUS: Forwarding
DESCRIPTION: The root switch is always the designated switch on all connected segments (Odom, 2013 p.26) |
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CHARACTERIZATION of PORT |
STP STATUS: Forwarding
DESCRIPTION: The port through which the switch has the least cost to reach the root switch (lowest root cost) (Odom, 2013 p.26) |
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CHARACTERIZATION of PORT |
STP STATUS: Forwarding
DESCRIPTION:The switch forwarding the hello on to the segment, with the lowest root cost, is the designated switch for that segment (Odom, 2013 p.26) |
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CHARACTERIZATION of PORT |
STP STATUS: Blocking
DESCRIPTION: The port is not used for forwarding user frames, nor are any frames received on these interfaces considered for forwarding. (Odom, 2013 p.26) |
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What fields are in the STP Hello BPDU?
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1. Root Bridge
2. Sender's Bridge 3. Sender's root cost 4. Timer values on the root switch (Odom, 2013 p.27) |
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What is the root bridge ID
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The bridge ID of the switch the sender of this hello currently believes to be the root switch.
(Odom, 2013 p.27) |
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What is the sender's bridge ID?
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The bridge ID of the switch sending this hello BDPU
(Odom, 2013 p.27) |
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What is the sender's root cost |
The STP cost between this switch and the current root
(Odom, 2013 p.27) |
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What is the Timer values on the root switch?
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Includes the hello timer, MaxAge timer and forward delay timer
(Odom, 2013 p.27) |
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Summarizing the root election happens through each switch claiming to be root, with the best switch being elected based on the numerically lowest bid. Breaking down the BID into its components, the comparisons can be made as?
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- The lowest Bid
- If that ties, the lowest switch MAC address (Odom, 2013 p.29) |
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DEFAULT PORT COSTS ACCORDING to IEEE |
IEEE COST
100 (Odom, 2013 p.33) |
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DEFAULT PORT COSTS ACCORDING to IEEE
100 Mbps |
IEEE COST
19 (Odom, 2013 p.33) |
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DEFAULT PORT COSTS ACCORDING to IEEE |
IEEE COST
4 (Odom, 2013 p.33) |
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DEFAULT PORT COSTS ACCORDING to IEEE
10 Gbps |
IEEE COST
2 (Odom, 2013 p.33) |
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DEFAULT PORT COSTS ACCORDING to IEEE
100 Gbps |
IEEE COST
1 (Odom, 2013 p.33) |
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What is the steady state operation when nothing is currently changing in the STP topology? |
STEP 1: The root creates and sends a hello BPDU, with a root cost of 0, out all its working interfaces (those in a forwarding state).
STEP 2: The nonroot switches receive the hello on their root ports. After changing the hello to list their own BID as the sender's BID, and listing that switch's root cost, the switch forwards the hello out all designated ports STEP 3: Steps 1 and 2 repeat until something changes (Odom, 2013 p.33) |
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STP Timers
Hello |
The time period between
(Odom, 2013 p.34) |
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STP Timers
Max Age |
How long any switch should wait, after ceasing to hear hellos, before trying to change the STP topology.
(Odom, 2013 p.34) |
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STP Timers
Forward delay |
Delay that affects the process that occurs when an interface change3s from blocking state to forwarding state. A port stays in an interim listening state, and then an interim learning state, for the number of seconds defined by the forward delay timer.
(Odom, 2013 p.34) |
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What occurs during a listening state?
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Like the blocking state, the interface does not forward frames. The switch removed old stale (unused) MAC table entries for which no frames are received from each MAC address during this period. These stale MAC address table entries could be the cause of the temporary loops.
(Odom, 2013 p.36) |
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What occurs during a learning state?
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Interfaces in this state still do not forward frames, but the switch begins to learn the MAC address of frames received on the interface.
(Odom, 2013 p.36) |
