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31 Cards in this Set
- Front
- Back
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Command to show dynamic mac addresses |
show mac-address-table dynamic |
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How long to mac address stay in table? What is command to view this time? |
show mac-address-table aging-time The default is 300 sec or 5 min |
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Command to configure static MAC address entry |
mac address-table static <6 byte MAC address> vlan interface |
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Command mac addressed to be dropped? |
mac address-table static <6 byte mac address> vlan drop |
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Command to disable learning on a VLAN |
no mac address-table learning vlan |
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What is error disable? And what reasons can an interface go into error disable? |
Software shuts down interface because error condition has occurred. The LED turns orange. Originally this was developed for excessive collisions, duplex mismatch, and bad NICs. Later other software things where added - port security violations, STP, Etherchannel issues, DHCP snooping rate limit, ARP inspection, PaGP. |
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What command will show interface in error disabled state? |
show interface status interface status will show error disabled |
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What is errdisable recovery? How to configure error disable recovery for port security and then all? |
This provides the software the ability to enable and error disabled port. errordisable recovery cause psecure-violation errordisable recovery cause all |
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What commands shows what protocols have been enabled for errdisable-recovery? What is the default timer? How to change the interval? |
show errdisable-recovery 300 seconds errordisable recovery interval 300 |
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What happens if a port reaches the end of the error recovery period but still has the same issue? |
It will enter into a error disable period again. |
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What is CDP? What are the CDP timers? What is the destination MAC address of a CDP frame? |
Cisco Discovery Protocol. Useful for gathering info about neighboring switch. CDP sent every 60 seconds with holdtime of 180 Sent to a multicast address 0100.0ccc.cccc. Same address as VTP, DTP, UDLD, PAgP |
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What is included in a CDP packet? |
Device Name, IOS Version, Hardware capabilities (switch, router), platform, layer 3 capabilities, interface CDP packet generated on, VTP domain, native VLAN of sending port, MTU, and duplex |
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Who to disable globally and per interface? |
no cdp run interface x/x no cdp enable |
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What command show all CDP neighbors? What command shows detailed information? Most people show cdp neighbor based on interface. How to show based on hostname? |
show cdp neighbors show cdp neighbors detail show cdp neighbors will reveal the device ID of the neighbor. show cdp entry will provide the detailed information. |
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What is LLDP? What is industry standard designation? What are the LLDP timers? |
Industry version of CDP 802.1AB sent every 30 and holdtime of 120 |
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How to enable globally and per interface? |
lldp run interface x/x lldp transmit lldp receive |
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What are the differences between LLDP and CDP? |
LLDP duplex, speed, TCN, third-party devicesCDP duplex, MTU, VTP, Native VLAN |
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What is UDLD and what does it protect against? |
Unidirectional Link Detection. It looks for unidirectional links in the networks which can cause loops. Usually with fiber optics networks this may occur. STP requires bi-directional communication during initialization. A unidirectional link can lead to a loop. |
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How is UDLD different from loopguard? How does UDLD work? |
Loopguard uses STP packets to protect and UDLD uses it's own packets. It forwards UDLD packets with device ID and port ID to the well known multicast address of 0100.0ccc.cccc. The remote switch should respond with device ID and port id and echo all the neighbors it knows back. |
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What is implicit detection? What is explicit detection? |
If no echo back and link is up this is an implicit UD link. UDLD mode determines action. Explicit detection. If no echo frames with my switch ID. If the switch has detected only one neighbor but my neighbor suggest there are many by echoing several. If I see my self as |
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The action that is taken is determined by what? Describes the possible actions. |
The mode of operation determines the action. There are two modes. Aggressive and normal. In notmal port continues operation. It sends 8 messages, 1 per second in attempt to reestablish. UDLD marks as undetermined and generates syslog message. Aggressive sends 8 messages /sec. If none it places in err-disabled. In normal mode it can error disable in certain conditions. |
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What stops UDLD from disabling port when things are first coming up? |
UDLD waits to hear a neighbor before it considers taking any action. |
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Can UDLD be enabled per port or globally? Configure. |
Both (config)udld {enable | aggressive | message time seconds } (config-if)udld {enable | aggressive | disable } |
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What does "system mtu mtu" do? |
It changes the MTU on all 10/100 interfaces. Interface cannot be modified individually. |
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What does "system jumbo mtu mtu" do? |
It changes the MTU on all 1Gbps and higher interfaces. Cannot be changed individually. |
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What must be done for system mtu command to take affect? |
Must reload the switch. |
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What does system routing mtu configure? |
It configures the MTU for all SVIs |
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What is the default UDLD timer? What is the range? What does Tdetection<Tconvergence mean? |
UDLD sends messages every 15 seconds. The range is 7 - 90 seconds. Timeout is 45 seconds. 45 is Tdetection and Tconvergence is STP which is 50 seconds. |
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What is Fast UDLD? |
Fast UDLD supports sub seconds UDLD messages. |
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What does this command do? Router(config)# udld fast-hello error-reporting |
By default Fast UDLD places port into error disable. This cause device to send a message instead. |
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What does this command do? Router# udld reset |
This commands resets all UDLD ports that are in error disable mode. |
