ICND2 Section 1 - LAN Switching Flashcards Preview

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Flashcards in ICND2 Section 1 - LAN Switching Deck (31)
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1

3 problems caused by not using STP

1. Broadcast Storms
2. MAC table instability
3. Multiple copies of the same frame delivered to a host.

2

What types of packets are processed by a port in Blocking?

STP control traffic only

3

4 general steps for a switched network to get from nothing to full STP convergence

1. Elect a root switch
2. Select the root ports
3. Select the Designated ports
4. Select the Blocked ports

4

What does BPDU stand for?

Bridge Protocol Data Unit

5

What is the BID?
How is it calculated?

Bridge ID
2 byte priority field + 6 byte system ID (BIA)

6

For STP, is higher or lower priority better?

Lower

7

In STP, if the priority is equal, what is used to determine the root bridge?

The lowest System ID, aka MAC address used in the BID

8

How is cost to the root bridge calculated?

The sum of all ports exited to reach the root bridge

9

How does a switch determine it's neighbor's cost to get to the root bridge?

It's a value listed in the neighbor's BPDU root cost.

10

What is the default bridge priority?

32768

11

STP IEEE standard?

802.1D

12

Time interval for BPDUs

2 seconds

13

4 STP port states

Listening
Learning
Forwarding
Blocking

14

Roughly speaking, what is used to calculate STP port cost

Port Speed

15

What is a switch doing while a port is in Listening

Listening for and processing BPDUs, trying to see if it gets any info that would cause it to go to a Blocking state.

16

Does a switch populate the MAC table while in Listening?

No

17

What is a switch doing in Learning?

Learning source MAC addresses and populating the MAC address table, preparatory to beginning Forwarding.

18

Default STP port costs for the following speeds:
10M
100M
1G
10G

10M = 100
100M = 19
1G = 4
10G = 2

19

When a non-root switch receives a Hello BPDU, what does it change before forwarding it on?

It adds it's root cost to the root cost present in the BPDU.

20

What are the 3 types of BPDUs?

Hello BPDU
CBDPU - Configuration BPDU
TCN BPDU - Topology Change Notification BPDU

21

Command to configure an etherchannel

conf t
interface *int*
channel-group *group number* mode on

22

Command to show the status of an etherchannel

show etherchannel *group number*

23

What are the 2 protocols that can be used to create dynamic etherchannels?

PAgP
LACP

24

What does PAgP stand for?

Port Aggregation Protocol

25

What does LACP stand for?

Link Aggregation Control Protocol

26

What is the IEEE standard for PAgP and LACP?

PAgP is Cisco proprietary
LACP is 802.1ad

27

Syntax to enable PAgP on a interface

conf t
int gi1/0
channel-group *group number* mode {desirable | auto}

28

Syntax to enable LACP on a interface

conf t
int gi1/0
channel-group *group number* mode {active | passive}

29

In PAgP configurations, what does the keyword desirable tell the switch to do vs auto?

It tells the switch “use this protocol and begin negotiations”
versus “use this protocol and wait for the other switch to begin negotiations.”

30

In LACP configurations, what does the keyword active tell the switch to do vs passive?

It tells the switch “use this protocol and begin negotiations”
versus “use this protocol and wait for the other switch to begin negotiations.”