Flashcards
1.5 Configure and verify EtherChannels
Cards in this deck (63)
- 1What are the purpose of etherchannels?EtherChannel provides fault-tolerant high-speed links between switches, routers, and servers.
- 2How many links can be part of a PAgP etherchannel?2-8
- 3What is the throughput of a FastEthernet link? (Fa)200 Mbps
- 4How does etherchannel avoid loops when using so many links?All the links act as a single logical link
- 5Does an ethernet bundle operate at the full combined throughput of all its links?no. The load is not evenly distributed across all links. Some links might carry more and they only operate at their inherent speed.
- 6what happens if a link in an etherchannel fails?the traffic is moved to an adjacent link
- 7What is MEC?Multichassis EtherChannel (MEC)
a portchannel that is made up of ports across different physical switches within a stack (so if a switch goes down, etherchannel keeps working!) - 8What conditions do ports need to meet before they can be bundled into an etherchannel?They need to all have the same config
- 9How does the creating an etherchannel differ when working with L3 ports as opposed to L2 ports?L2 you start with channel-group
L3 must first start with interface port-channel followed by no switchport and THEN channel-group - 10After creating a channel-group, how do configuration changes affect the ports in the groupchanges made to the channel group affect all ports in the group
- 11What are two etherchannel negotiation protocols?Port Aggregation Protocol PAgP (cisco)
Link Aggregation Control Protocol LACP(RFC) - 12How many ports can be part of an LACP etherchannel?16
8 Active
8 Standby - 13What is a shutdown port treated as in an etherchannel?treated as a link failure
- 14Can you configure a port to be a member of more than one etherchannel?no
- 15Can PAgP and LACP exist on the same switch?Yes. But they cant mix within a single etherchannel. You can't have some ports in an EC running PAgP and others running LACP
- 16can a secure port be part of an etherchannel?no.
- 17can a private-vlan port be part of an etherchannel?no
- 18where does PAgP form etherchannels?on ports that are4 configured for either identical staic valns or trunking
- 19What are the 3 PAgP negotiation modes?Auto (passive, won't actively try to form)
Desirable (tries to form an etherchannel)
On (doesn't exchange PAgP packets)
auto is default - 20How do you configure the ethernchannel negotiation protocol for a range of ports?Switch(config-if-range)# channel-protocol pagp
Switch(config-if-range)# channel-group 5 mode desirable non-silent - 21what is the purpose of silent vs non-silent with PAgP?silent is for when the etherchannel is connected to a device that can't do PAgP (like a server that still needs the EC throughput) Silent doesn't bother sending PAgP packets.
non-silent for when you know the device on the other end can do PAgP - 22what is a physical learner?A device is a physical learner if it learns addresses by physical ports and directs transmissions based on that knowledge.
- 23what is an aggregate-port learner?A device is an aggregate-port learner if it learns addresses by aggregate (logical) ports. The learn method must be configured the same at both ends of the link.
- 24what happens when 2 devices are both aggregate port learners?The learn from the packets sent on any of their logical port-channel ports
- 25How does PAgP know the learning method to use?It doesn't. You have to manually set the learning method on the local device to learn addresses by physical ports
- 26How must load-distribution method be configured on PAgP?You also must set the load-distribution method to source-based distribution, so that any given source MAC address is always sent on the same physical port.
- 27What is the default learning method of PAgP?By default, aggregation-port learning is selected, which means the switch sends packets to the source by using any of the ports in the EtherChannel.
- 28what is the command to configure the learn method of an int?SW1(config-if)# pagp learn-method ?
- 29what is the purpose of configuring port priority on PAgP?to change the frequency with which a particular port is chosen to send packets over
- 30how can you verify etherchannel information?Switch# show etherchannel [channel-group-number {detail | port | port-channel | protocol | summary}] {detail | load-balance | port | port-channel | protocol | summary}
- 31how can you verify PAgP information?Switch# show pagp [channel-group-number] {counters | internal |neighbor}
- 32how can you clear PAgP info and counters?Switch# clear pagp {channel-group-number counters | counters}
- 33Where does a layer 2 etherchannel get it's mac address from?the first port in the channel that comes up
- 34Where does a layer 3 etherchannel get its mac addressfrom the stack master as soon as the channel is created
- 35can CDP and DTP information traverse etherchannels?Yes, over the physical ports.
Trunk ports send and receive PAgP protocol data units (PDUs) on the lowest numbered VLAN. - 36what comprises the system priority of a switch in an LACP etherchannel?a 2-byte priority value followed by a 6-byte switch MAC address
- 37what comprises port priority in an LACP etherchannel?a 2-byte priority followed by a 2-byte port number
- 38In an LACP EC, what indicates a higher port priority?a lower value
- 39What are the 2 LACP negotiation Modes?Active mode can form an EtherChannel with another port that is in the active or passive mode.
Passive mode cannot form an EtherChannel with another port that is also in the passive mode because neither port starts LACP negotiation. - 40What is the LACP default System Priority?32,768
- 41If both switches have the same priority, which one wins and is able to make decisions about the etherchannel?the one with the lower MAC address
- 42What is the LACP priority range?1 to 65,535
- 43how can you verify LACP?Switch# show lacp [channel-group-number] {counters | internal |neighbor}
- 44What is the purpose of ON mode in ECs?ON mode is used to manually configure an EtherChannel. The ON mode forces a port to join an EtherChannel without negotiations. It can be useful if the remote device does not support PAgP or LACP. In ON mode, a usable EtherChannel exists only when the switches at both ends of the link are configured in ON mode.
- 45how is traffic sent over an Etherchannel?frames are forwarded on a specific link as a result of a hashing algorithm. The algorithm can use source IP, destination IP, or a combination of source and destination IP, source and destination MAC, or TCP/UDP port numbers. The hash algorithm computes a binary pattern that selects a link number in the bundle to carry each frame.
- 46what is the default algorithm on cisco switches to decide what link in an EC will be used to send traffic?default ether-channel load-balance algorithm is “XOR source and destination IP ” to do the load-balance.
- 47A note on forwarding:frames from the same source or to the same destination are sent over the same link. Same with packets sent to a particular device. Other stuff is load balanced. ?
- 48how can you verify EC load balancing configuration?Switch# show etherchannel load-balance
- 49How can you see detailed informatiopn about a port-channel?SW1# show etherchannel port-channel
- 50What must you first do when creating layer 3 ether channels?To configure Layer 3 EtherChannels, you first create the port-channel logical interface and then put the Ethernet ports into the port-channel as described next.
- 51how would you create a logical etherchannel interface?Switch# configure terminal
Switch(config)# interface port-channel 5
Switch(config-if)# no switchport
Switch(config-if)# ip address 172.10.20.10 255.255.255.0
Switch(config-if)# end - 52How would you configure the physical ports to belong to channel 5 in LACP mode active?Switch# configure terminal
Switch(config)# interface range gigabitethernet0/1 -2
Switch(config-if-range)# no ip address
Switch(config-if-range)# no switchport
Switch(config-if-range)# channel-group 5 mode active
Switch(config-if-range)# end - 53How can you easily identify if LACP or PAgP is being used simply by looking at the modes?PAgP uses Desirable or Auto
LACP uses Active or Passive - 54What is EtherChannel Guard?a feature that will detect if there's been an Etherchannel misconfiguration and shut down the ports involved and put them in err-disabled state and raise a warning
- 55How do you enable etherchannel guard?Switch(config)# [no] spanning-tree etherchannel guard misconfig
- 56What is important to remember about ECs when troubleshooting them?that the whole concept is based on consistent configurations on both ends of the channel.
- 57remember:EtherChannel desirable (PAgP) or active (LACP) mode attempts to ask the far end to bring up a channel. Therefore, the other end must be set to either desirable or auto mode.
- 58remember:EtherChannel auto (PAgP) or passive (LACP) mode participates in the channel protocol, but only if the far end asks for participation. Therefore, two switches in the auto or passive mode will not form an EtherChannel.
- 59remember:PAgP desirable and auto modes default to the silent submode, in which no PAgP packets are expected from the far end. If ports are set to non-silent submode, PAgP packets must be received before a channel will form.
- 60what is the very first command you should run when troubleshooting ECs?Switch# show etherchannel summary
- 61How can you see detailed port information?Switch# show etherchannel port
- 62How can you verify a port's configuration?SW# show running-config interface gig0/0/0
SW# show interface gig0/0/0 etherchannel - 63how can you verify the etherchannel hashing algorithm?SW# show etherchannel load-balance
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- CWNA Networking (CCNP Switch Exam Topics) Flashcards on 1.5 Configure and verify EtherChannels, created by Dustin Sanders on 21/01/2017.
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- Created by Dustin Sanders · Jan 21, 2017
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