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Cisco CCNA 200-125 > LAN Switching > Flashcards

Flashcards in LAN Switching Deck (19)
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What causes the risk of a layer 2 loop forming in a switch topography

A frame unlike a packet does not have a TTL field in the packet or Time To Live field, so it could loop around in the topography forever


What happens if the same Mac address comes into another port of a switch

The Mac address table will be updated such that the Mac address will now be listed under the other port


How is a root switch elected in a topography

The switch with the lowest bridge id (and Mac address if there needs to be a tiebreaker) is elected to be the root switch


What are the four spanning tree protocol port states

Root port - non root switch port closest to root switch (lower interface on root switch if there needs to be a tie breaker), Designated port - one for each segment, port closer to root switch, rest are blocked ports


The higher the speed of the link in a network topography running spanning tree,

the lower the cost of the link


What's the traditional convergence time of STP and how is it broken down

Total 50 seconds, 20 seconds blocking and waiting for BPDU, Listening State: 15 seconds, Learning State: 15 Seconds


What is BPDU

Bridge Protocol Data Unit


What is the difference between PVST and PVST+

PVST (Per VLAN Spanning Tree) is used over ISL trunks while PVST+ is used over IEEE 802.1Q trunks


What is RSTP

Rapid PVST+ fast convergence, one instance for each VLAN


What are the three port states of PVST+

Discarding, Learning, Forwarding (No Listening State Here)


What's different about rapid STP

sends a BPDU to all neighbors instead of TCN TCA and then TC BPDU


What is VLAN Trunking Protocol

You set a new VLAN in one of the center VLANS and the switch sends VTP advertisements out of their trunk ports, allowing each switch down the way to learn that there's a new VLAN


What is a client mode for a switch

The switch is updated with VLAN information advertisements, but cannot modify or change it, can originate and forwards VTP messages


What is server mode for a switch

The switch can change VLANs and any changes are propogated across the network


What is transparent mode for a switch

You can make changes to the local database but the changes are not advertised over the trunk ports and does not update its database from advertisements, no orign of VTP advertisements but receives VTP messages and forwards them


What is an alternate port in RPVST

Alternate way to get to root bridge


What is a backup port in RPVST

When there's a redundant link on a shared segment (such as two connections to a hub)


What is port fast

Port fast, under the condition that the port connects to an endpoint on the network, activates immediately. With port fast, the Listening and Learning stages are skipped; available only on non-trunking ports (so no switch to switch)


What is BPDU guard

In whatever case when one connects a switch to a supposed portfast connection, BPDU guard will transition to block any BPDU sent out and put the port down into err disable mode to prevent a topological loop