Study Guide Flashcards
What are the two types of packets routers use?
Data packets and route update packets.
What is a window?
A window defines the amount of data a transmitting device can send before it has to stop and wait for an acknowledgement. It’s a layer 2 concept. A smaller window can better ensure data integrity but it will result in a slower, more laborious transmission of data.
Why is it that routers “break up broadcast domains” but switches don’t?
Because routers, by default, block broadcasts and multicasts. Switches flood them.
On what layer of the OSI reference model does a hub act?
The physical layer only - it merely repeats the signals it receives.
What are the three things to remember about full duplex mode?
• There are NO collisions in full
duplex mode
• A dedicated switch port is required
for each full duplex node
• Both the NIC and the switch port
must be capable of running full
duplex mode
What is the highest-order bit in a MAC address when used in Ethernet addressing?
Is the Individual/Group bit (I/G). If it’s turned off it means that the MAC address belongs to a single device and can be used for a unicast. If it’s on, the following address is a broadcast address.
What is the second-highest-order bit?
The global/local (g/l) bit
What’s the IEEE standard for all 10 Mbps cabling? What’s the standard for 100 Mpbs (fast Ethernet) physical media?
- 3
802. 3u
What are the three types of cable that can be created from an Ethernet cable? What are they used to connect?
• straight-through - used to connect a
PC to a switch or a switch to a router
• crossover - used to connect a switch
to a switch, PC to PC, hub to hub or
hub to switch
• rolled - used for a console connection
between a PC and a switch or router
ICMP functions on what layer?
Layer 3
What’s the only difference between Ethernet and Ethernet_II headers?
The Ethernet_II header uses a Type field instead of a Length field.
RARP
Reverse Address Resolution Protocol
RARP translates a MAC address into an IP address. Diskless devices initially don't know their
Which layer 4 protocol(s) and port number(s) does DHCP use?
UDP 67, 68
Which layer 4 protocol(s) and port number(s) does telnet use?
TCP 23
Which layer 4 protocol(s) and port number(s) does FTP use?
TCP 21
Which layer 4 protocol(s) and port number(s) does TFTP use?
UDP 69
Which layer 4 protocol(s) and port number(s) does DNS use?
TCP/UDP 53
Which layer 4 protocol(s) and port number(s) does HTTP use?
TCP 80
Which layer 4 protocol(s) and port number(s )does SNMP use?
UDP 161
Which layer 4 protocol(s) and port number(s) does SMTP use?
TCP 25
What is the IPv4 class A private address space?
10.0.0.0 - 10.255.255.255
What is the IPv4 class B private address space?
172.16.0.0 - 172.31.255.255
What is the IPv4 class C private address space?
192.168.0.0 - 192.168.255.255
What are classful and classless routing protocols?
One that assumes that all devices in the network share the same subnet mask, and therefore does not send subnet mask information along with its routing updates.
Classless routing protocols include subnet masks with their routing updates - this makes them compatible with networks that employ variable length subnet masks.
Group the following dynamic routing protocols into classful and classless: RIP, OSPF, EIGRP, IGRP, RIPv2
Classful: IGRP, RIP
Classless: EIGRP, RIPv2, OSPF
In an Ethernet II frame, what does the Type field tell the data link layer?
Which protocol should handle the packet after it’s passed up to layer 3.
What is the command to activate RIP?
What else do you have to do in order for it be functional?
Corp(config)#router rip
You also have to tell the router which network to advertise:
Corp(config-router)#network [IP]
What is the maximum hop count for RIP?
15
What is the default administrative distance for a static route? A directly connected route?
Static = 1
Directly Connected = 0
Why are distance vector DRPs prone to routing loops?
Because of their slow convergence time - when a route goes down, it takes a while for distant devices to receive an update relaying the fact. This can result in routing loops.
What are some measures taken to prevent routing loops?
Maximum hop count - RIP has a max hop count of 15, after the expiration of which the packet is discarded and the destination network deemed unreachable.
Split Horizon - prevents routers from sending updates out the interface on which they received them.
Route poisoning - when a route goes down it is advertised as having an administrative distance of 16 (more than 15; unreachable). This update is sent to all nodes on the network.
Holddowns - holddowns cause routers to wait for a time before considering a route “down” when it goes down or “up” when it comes back up. This prevents rapid, possibly inaccurate changes in routing tables because of a “flapping” route.
What is route redistribution?
Using two dynamic routing protocols simultaneously and in such a way that they can exchange routing information with each other.
When running EIGRP what three conditions must be met in order for routers to establish adjacencies?
- A “hello” or an ACK must have been received.
- The devices must be in the same autonomous system
- The devices must have identical metrics (K values)
In OSPF, what are the different categories of routers and what is each?
Internal routers exist within an OSPF area.
Area border routers connect routers from other areas to the backbone area (area 0).
Autonomous system boundary routers connect different autonomous systems.
When enabling the dynamic routing protocols RIP, EIGRP, and OSPF what information is necessary for each?
RIP - simply enable with config t and router RIP, then the networks to include with network then the IP address
EIGRP - enable in the same way but with router EIGRP, then an autonomous system number (which is not meaningful as long as all your routers have the same #). Then add networks in the same way.
OSPF - router OSPF
What are the three types of NAT? Which is the only type that allows conservation of registered IP addresses?
Static, dynamic, overloaded (PAT)
PAT is the only type that conserves IPs
What are source IPs called before they’re translated with NAT? After?
inside local
inside global
