Chap2er 5-6 Flashcards
Sem 2 Chap 5-6
What does STP do
logically blocks physical loops in layer 2 networks
What is the main function of STP
disables redundant paths to eliminate layer 2 loops
Outcome of broadcast storm
new traffic is discarded by the switch and unable to be processed
Problems when turning spanning tree off
MAC address table becomes unstable, broadcast frames are transmitted indefinitely
Network features that require STP
redundant links between Layer 2 switches, removing single point of failure with multiple Layer 2 switches
3 Components of bridge ID
Extended sys ID (VLAN #), MAC address, bridge priority
T/F: A bridge priority of 1 is the lowest valid bridge priority
False (increments of 4096)
Highest possible bridge priority
61440
If switch priority is all the same, the root switch is determined by
lowest MAC address
The root port is the port closest to the
root switch
What is used to determine the root port?
path cost
In which two roles can interfaces function in the forwarding state?
designated, root
In which two port states does a switch learn MAC addresses and process BPDUs in a PVST network
forwarding, learning
What STP field has a default value of 32768
bridge priority
What field is used to specify a vlan id
extended system id
What is the reference port for all path calculations
root bridge
What is a non-root port that is permitted to forward traffic across the network
designated port
What is the closest overall port to the root bridge (in terms of cost) called
root port
Spanning tree standard that supports only one root bridge
802.1D
Protocol that provides up to 16 instances of RSTP, combines many VLANs with the same phys/logi topology into common RSTP instance, and provides support for a bunch of stuff
MST
The Legacy standard for STP that runs all VLANS in a single spanning-tree instance
STP
Cisco enhancement of RSTP
Rapid PVST+
Protocol that allows multiple VLANs in a single spanning-tree instance
MSTP
Proprietary per-vlan implementation of ieee 802.1w
Rapid PVST+
Cisco Implementation of IEEE 802.1D
PVST+
Fast-Converging enhancement of IEEE 802.1D
RSTP
IEEE Standard that reduces the number of STP instances
MSTP
Standard that allows more bandwidth between a L3 switch and multiple L2 switches
EtherChannel
What happens if one of three configured links in an EtherChannel link goes down
other two interfaces continue to load balance traffic
Advantages of EtherChannel
consistency in configuration of physical links, views physical links in EtherChannel as one logical connection
Load-balancing methods of EtherChannel
src-dest IP, src-dest MAC
Reqs to be able to configure EtherChannel between two switches
interfaces at same speed and same duplex
T/F: PagP is a Cisco proprietary standard
TRUE
Two parameters that must match on ports of switches to create PagP EtherChannel between swtiches
speed, VLAN information
Mode to allow EtherChannel link formation without negotiation
both on
What happens if one EtherChannel is set to desirable but the other is set to on
EtherChannel link fails to establish
If one switch EtherChannel is set to auto, what should the other switch be set to
desirable
Open protocol standard that allows switches to bundle multiple ports
LACP
Advantages of LACP
Allows directly connected switches to negotiate EtherChannel link, allows multivendor devices
When EtherChannel is configured, what mode forces an interface into port channel without exchanging aggregation protocol packets
on
Two channel group modes to place interface in negotiating state w/ PagP
desirable, auto
Requirement to configure trunking EtherChannel between two switches
allowed VLANs must be the same
Exhibit where there’s an EtherChannel between two switches. What’s the problem
allowed VLANs are different
If a PortChannel shows PagP, what does that mean
it’s using a cisco proprietary protocol
What does a D mean in etherchannel output
not functional
