Fundamentals Flashcards
What are the two types of port queues on a switchport?
ingrees queues, and egress queues.
What is the max cable length of most X-BASE-T wiring?
100m (328 ft)
ACLs on a switch can identify frames based on what 5 features?
MAC address, non-IP protocol types, IP Addresses, Protocols, and Layer-4 port numbers.
If an error is detected on a switchport what happens to it?
It is placed in the errdisable state, and disabled.
What is the IEEE standard for 10 GigE?
802.3ae
If set to automatic recovery, an errdisabled port will stay down for how long? What is the range for configuring this time?
300 seconds, and 30-86,400 seconds.
What is the IEEE standard for Gigabit Ethernet? (over copper)
802.3ab
What is the IEEE standard for FastEthernet?
802.3u
Is duplex autonegotiation possible on Gigabit Ethernet?
No, because Gigabit Ethernet is, by definition, Full Duplex.
What is the IEEE standard for Gigabit Ethernet? (over fiber)
802.3z
What are the two Physical classifications of 10 GigE?
-LAN PHY, Connects switches, usually in the Core layer.-WAN PHY, Connects to SONET or SDH networks, typically in MANs.
Define auto-negotiation
Ethernet process by which devices attached to the same cable negotiate their speed and the duplex settings over the cable.
Define half duplex
Ethernet feature in which a NIC or Ethernet port can only transmit or receive at the same instant in time, but not both. Half duplex is required when a possibility of collisions exists.
Define full duplex
Ethernet feature in which a NIC or Ethernet port can both transmit and receive at the same instant in time. It can be used only when there is no possibility of collisions. Loopback circuitry on NIC cards is disabled to use full duplex.
Define crossover cable
Copper cable with RJ-45 connectors in which a twisted pair at pins 1,2 on the first end of the cable is connected to pins 3,6 on the other end, with a second pair connected to pins 3,6 on the first end and pins 1,2 on the other end.
Define straight-through cable
Copper cable with RJ-45 connectors in which the wire at pin 1 on one end is connected to pin 1 on the other end; the wire at pin 2 is connected to pin 2 on the other end; and so on.
Define loopback circuitry
A feature of Ethernet NICs. When the NIC transmits an electrical signal, it “loops” the transmitted electrical current back onto the receive pair. By doing so, if another NIC transmits a frame at the same time, the NIC can detect the overlapping received electrical signals, and sense that a collision has occurred.
Which feature describes MAC addresses that are dynamically learned or manually configured, stored in the address table, and added to the running configuration?
sticky
Each switch port is a _____ ______
collision domain
When a host is connected to a switchport, why aren’t frame errors propagated?
because each frame is checked
Which statement about using native VLANs to carry untagged frames is true?
Cisco Discovery Protocol version 2 carries native VLAN information, but version 1 does not.
What is a 10GE WAN PHY?
Connects with SONET or SDH
What pins does FE use?
1/2 and 3/6
What cabling do GBICs use?
SC fiber or RJ-45
Which fiber is the receive?
on the left as you face the connector
What types of ports autonegotiate?
FE and GE
What is the default 10mbps Enet duplex?
half-duplex
What is the default FE duplex?
Full duplex
How do you find duplex mismatches?
use sh interface on the interface and look for error counts > 10
By default, what layer do catalyst switchports operate on?
L2
What are the characteristics of the access layer?
low cost, high density ports, multiple scalable uplinks, vlans, traffic and protocol filtering and QoS
What are the characteristics of the distribution layer?
aggregation, high L3 throughput, security and policy based connectivity functions through access lists and packet filters, QoS, scalable high-speed links
what are the characteristics of the core layer
Very high L3 throughput, no access lists or port filtering, redundancy and resilience, advanced QoS
What is the core block?
the campus network’s backbone
What is the switch block?
Two distribution switches that aggregate one or more access switches
Where should multilayer switches be implemented?
Distribution layer
How many users should be within a switch block?
roughly 2000
How can you tell if a switch block is too large?
Routers at the distribution layer become the bottlenecks or broadcast or multicast traffic slows the switches in the switch block
What is the access layer best practice?
All L2 connectivity should be contained within the access layer.
What is the distribution layer best practice?
The distribution layer should have only L3 links
What criteria are used to size a switch block?
traffic types and patterns, amount of L3 switching cap. At dist. Layer, # users at access layer, geography, size of spanning tree domains
What is the over-subscriber ratio of Access-to-Distribution and Distribution-to-Core?
A-D 20:1, D-C 4:1
What is the pps rate for a 100BaseX network? Calculate it for the minimum and maximum frame sizes.
Because all of the bit time values are one tenth that of 10 Mbps Ethernet, the pps for 100 Mbps Ethernet is 10 times the 10 Mbps pps values. So Fast Ethernet supports up to 148,800 pps for 64 byte frames and 8,120 pps for 1518 byte frames.
What are the implications of mixing half-duplex and full-duplex devices? How do you do it?
You need to ensure that your full-duplex devices attach to full-duplex hubs. Otherwise, the full-duplex devices need to run in half-duplex mode. Always attach full duplex together and half duplex together.
What is the smallest Gigabit Ethernet frame size that does not need carrier extension?
The need for the carrier extension bytes is driven by the slotTime. Gigabit Ethernet uses a slot time for 4096 bits. This equates to 512 bytes. Therefore, any frames of 512 bytes or larger do not need carrier extension, whereas all frames less than 512 MUST have carrier extension.
If you attach a multiport repeater (hub) to a bridge port, how many broadcast domains are seen on the hub?
Legacy hubs have all ports in the same collision and broadcast domains, regardless of the internetworking device they attach to
Define I/G bit
The most significant bit in the most significant byte of an Ethernet MAC address, its value implies that the address is a unicast MAC address (binary 0) or not (binary 1).
Define U/L bit
The second most significant bit in the most significant byte of an Ethernet MAC address, a value of binary 0 implies that the address is a Universally Administered Address (UAA) (also known as Burned-In Address [BIA]), and a value of binary 1 implies that the MAC address is a locally configured address.
Define CSMA/CD
Carrier sense multiple access with collision detection. A media-access mechanism where devices ready to transmit data first check the channel for a carrier. If no carrier is sensed for a specific period of time, a device can transmit. If two devices transmit simultaneously, a collision occurs and is detected by all colliding devices. This collision subsequently causes each device to delay retransmissions of the collided frame for some random length of time.
Can a legacy bridge belong to more than one broadcast domain?
Generally, all ports on a legacy bridge belong to the same broadcast domain.
Define encapsulation
The process of taking a PDU from some other source and placing a header in front of the original PDU, and possibly a trailer behind it.
