CCNA2 - Module 5&6 Flashcards
is an important part of the hierarchical design for eliminating single points of failure and preventing disruption of network services to users.
Redundancy
True/False:
Ethernet LANs require a loop-free topology with a single path between any two devices.
True
is a loop-prevention network protocol that allows for redundancy while creating a loop-free Layer 2 topology.
logically blocks physical loops in a Layer 2 network, preventing frames from circling the network forever
Spanning Tree Protocol (STP)
compensates for a failure in the network by recalculating and opening up previously blocked ports.
STP
provides multiple network services by eliminating the possibility of a single point of failure.
Path redundancy
STP was developed specifically as a loop prevention mechanism for ________________________
Layer 2 Ethernet
is when the switch does not have the destination MAC address in its MAC address table and must forward the frame out all ports, except the ingress port.
unknown unicast frame
is an abnormally high number of broadcasts overwhelming the network during a specific amount of time.
can disable a network within seconds by overwhelming switches and end devices. Broadcast storms can be caused by a hardware problem such as a faulty NIC or from a Layer 2 loop in the network.
broadcast storm
To prevent these issues from occurring in a redundant network, some type of ___________ must be enabled on the switches.
spanning tree
T/F:
Spanning tree is enabled manually on Cisco switches
False
it is enabled by default
STP is based on an algorithm invented by __________ while working for Digital Equipment Corporation, and published in the 1985 paper "An Algorithm for Distributed Computation of a Spanning Tree in an Extended LAN.”
Radia Perlman
creates a loop-free topology by selecting a single root bridge where all other switches determine a single least-cost path.
spanning tree algorithm (STA)
-is the interval between BPDUs. The default is 2 seconds but can be modified to between 1 and 10 seconds.
Hello Timer
- is the
time that is spent in the listening and learning state. The default is15 secondsbut can be modified to between4 and 30 seconds.
Forward Delay Timer
- is the
maximum length of time that a switch waits before attempting to change the STP topology. The default is20 secondsbut can be modified to between6 and 40 seconds.
Max Age Timer
versions of STP, there is a root bridge elected for each spanning tree instance. This makes it possible to have different root bridges for different sets of VLANs.
Per-VLAN Spanning Tree (PVST)
: This is the original IEEE 802.1D version (802.1D-1998 and earlier) that provides a loop-free topology in a network with redundant links. Also called Common Spanning Tree (CST), it assumes one spanning tree instance for the entire bridged network, regardless of the number of VLANs.
STP
: is a Cisco enhancement of STP that provides a separate 802.1D spanning tree instance for each VLAN configured in the network.
* supports PortFast, UplinkFast, BackboneFast, BPDU guard, BPDU filter, root guard, and loop guard.
Per-VLAN Spanning Tree (PVST+)
: This is an updated version of the STP standard, incorporating IEEE 802.1w.
802.1D-2004
or IEEE 802.1w is an evolution of STP that provides faster convergence than STP.
Rapid Spanning Tree Protocol (RSTP)
: This is a Cisco enhancement of RSTP that uses PVST+ and provides a separate instance of 802.1w per VLAN. Each separate instance supports PortFast, BPDU guard, BPDU filter, root guard, and loop guard.
Rapid PVST+
is an IEEE standard inspired by the earlier Cisco proprietary Multiple Instance STP (MISTP) implementation. MSTP maps multiple VLANs into the same spanning tree instance.
Multiple Spanning Tree Protocol (MSTP)
is the Cisco implementation of MSTP, which provides up to 16 instances of RSTP and combines many VLANs with the same physical and logical topology into a common RSTP instance. Each instance supports PortFast, BPDU guard, BPDU filter, root guard, and loop guard.
Multiple Spanning Tree (MST)
supersedes the original 802.1D while retaining backward compatibility
RSTP (IEEE 802.1w)
EtherChannels can be formed through negotiation using one of two protocols, ___________-. These protocols allow ports with similar characteristics to form a channel through dynamic negotiation with adjoining switches.
Port Aggregation Protocol (PAgP) or Link Aggregation Control Protocol (LACP)
is a Cisco-proprietary protocol that aids in the automatic creation of EtherChannel links.
PAgP (pronounced “Pag - P”)
helps create the EtherChannel link by detecting the configuration of each side and ensuring that links are compatible so that the EtherChannel link can be enabled when needed.
PAgP
The modes for PAgP as follows:
On-This mode forces the interface to channel without PAgP. Interfaces configured in the on mode do not exchange PAgP packets.
PAgP desirable-This PAgP mode places an interface in an active negotiating state in which the interface initiates negotiations with other interfaces by sending PAgP packets.
PAgP auto-This PAgP mode places an interface in a passive negotiating state in which the interface responds to the PAgP packets that it receives but does not initiate PAgP negotiation.
The modes must be compatible on each side. If one side is configured to be in auto mode, it is placed
is part of an IEEE specification (802.3ad) that allows several physical ports to be bundled to form a single logical channel.
Link Aggregation Control Protocol (LACP)
provides the same negotiation benefits as PAgP. It helps create the EtherChannel link by detecting the configuration of each side and making sure that they are compatible so that the EtherChannel link can be enabled when needed
Link Aggregation Control Protocol (LACP)
The modes for LACP are as follows:
On-This mode forces the interface to channel without LACP. Interfaces configured in the on mode do not exchange LACP packets.
LACP active-This LACP mode places a port in an active negotiating state. In this state, the port initiates negotiations with other ports by sending LACP packets.
LACP passive-This LACP mode places a port in a passive negotiating state. In this state, the port responds to the LACP packets that it receives but does not initiate LACP packet negotiation.
The following guidelines and restrictions are useful for configuring EtherChannel:
- EtherChannel support-All Ethernet interfaces must support EtherChannel with no requirement that interfaces be physically contiguous.
- Speed and duplex-Configure all interfaces in an EtherChannel to operate at the same speed and in the same duplex mode.
- VLAN match-All interfaces in the EtherChannel bundle must be assigned to the same VLAN or be configured as a trunk (shown in the figure).
- Range of VLANs-An EtherChannel supports the same allowed range of VLANs on all the interfaces in a trunking EtherChannel. If the allowed range of VLANs is not the same, the interfaces do not form an EtherChannel, even when they are set toautoordesirablemode.
