CISCO ENCOR 350-401

Question 1

Dynamic Link Aggregation Protocols

Answer 1

Link Aggregation Control Protocol (open industry standard)

Port Aggregation Control Protocol (Cisco proprietary)

Question 2

Port Aggregation Protocol (PAgP)

Answer 2

MAC Address 0100:0CCC:CCCC
Protocol Code 0x0104

Modes:
Auto > does not initiate an Etherchannel and does not transmit PAgP packets out. If PAgP packet is received from remote switch the interface responds and then can establish a PAgP adjacency.
If both Devices are PAgP Auto, a PAgP does not form.

Desirable > an interface tries to establish an EtherChannel and transmit PAgP packets out of it. Active PAgP interfaces can establish a PAgP adjancery if the remote interface is configured to auto or desiable.

Question 3

Link Aggregation Control Protocol

Answer 3

MAC address > 0180:C200:0002

Passive: Interface does not initiate an etherchannel and does not transmit LACP packets. If a remote switch sends LACP packets the interface responds and then can estrablish LACEP ajacency. If both passive then no etherchannel.

Active: An Interace tries to establish an Etherchannel and transmit LACP packets out of it . Active LACP interfaces can estabish an LACP adjaceny if the remote interface is configured to active or passive.

Question 4

EtherChannel Bundle

Answer 4

If both switches have available porsts with faster throughout then the current link then changeing the link to higher speed interfaces solved the bandwith contingency problem however if would be nice to plug a second cable and double the bandwidth between switches. However STP will place one of the ports in a blocking state to prevent fowarding loops.

THe Physical link can be aggregated into a logical link called an EtherChannel Bundle.
The physical interfaces that are used to assemble the logical Etherchannel are called member interfaces.
STP works on local link not on physical link.

Etherchannel can be used for either layer-2 (access-trunk) or Layer3 routed forwarding.

A Switch can sucessfully form an ether channel by statically setting them to an state or by using dynamic link agggregation protocol to detect connectivity between devices.

Question 5

Ether-channel Configurations

Answer 5

Going into interface configration mode for the member interfaces and assigning them to an EtherChannel ID and configuring the appropriate mode

Static EtherChannel > channel-group (etherchannel id) mode on

LACP Etherchannel > channel-group (etherchannel id) mode {active | passive}

PAgP Etherchannel > channel-group (etherchannel id) mode on {auto | desirable} [non silent]

by Default PAgP operate in silent mode, which allows a port to establish an etherchannel with a device that is not PAgP capable.

non-silent requries a port to receive PAgP packets before adding it to the etherchannel, quick link establishment.

Question 6

Factors considered with Ether Channel Config

Answer 6

Configration settings for the etherchannel are palced int he port channel interface

member interfaces needs to be in Layer2 or Layer3, before being associated with the port channel.

Question 7

Port Channel Configration

Answer 7

SW1(config)# interface range gi1/0/1-2
SW1(config-if-range)# channel-group 1 mode active SW1(config-if-range)# interface port-channel 1 SW1(config-if)# switchport mode trunk

Question 8

show etherchannel summary

Answer 8

The first thing that should be checked is the etherchannel status which is listed in port channel column.

U : Working properly
D : interface down
M : mimumum number of active int
S : Layer 2 port channel interface
R : Layer 3 port channel interface
P : Participating and forwarding traffic
H : Maximum number of active int
  I : no LACP activity 
w : time left to erecieve a packet from neighbour
s   : suspended mode
r   : the switch module has been removed from chasis

Question 9

show interface port-channel (port channel id)

Answer 9

Logical interface can be viewed, the output includes traditional interface statistics and list member interfaces and indicates the badwidth reflects the compined throughput of all active member interfaces.

Question 10

Etherchannel Neighbours

Answer 10

show ehterchannel port displays detailed instances of the local configration and information from packets, too much information

LACP > show lacp neighbor
neighbor system id, system priority and slow or fact LACP packet

PAgP > show pagp neighbor
neighbor system id, remote port number and slow or fast PAgP packet intervels

Question 11

Verifying Etherchannel Packets

Answer 11

Verification of Etherchannel counters for appropriate protocol

LACP
Show lacp counters > etherchannel interfaces, assiciated member interfaces, counters for LACEP packets sent/recieved and any errors.

Clear lacp counters

PAgP
show pagp counters > etherchannel interfaces, assiciated member interfaces, counters for LACEP packets sent/recieved and any errors.

Clear pagp counters

Question 12

LACP Fast

Answer 12

Original LACP sent out packets every 30 sec.
A link is deemed unusable if the packet is not recieved after 3 intervals.

LACP packets are advertised every 1 sec
LACP fast

SW1(config)# interface range gi1/0/1-2
SW1(config-if-range)# lacp rate fast

SW1# show lacp internal
Flags: S - Device is requesting Slow LACPDUs
F - Device is requesting Fast LACPDUs
A - Device is in Active mode