Network+ Guide to Networks Chapter 4

How many fields in the trailer of a Frame?

1 - just the FCS (frame check sequence)

A TCP header contains how many fields?

10

How many fields are in an IPv4 header?

14

What is the MAX hop count for RIP?

15

The TCP header length can be between ____ and ___ bytes.

20 and 60 bytes, represented by 4 bits (each bit representing an increment of 4)

RIPv1 broadcasts routing tables every ___ seconds to other routers, regardless of whether the tables have changed.

30

Each row in a TCP segment/datagram is made of ___ bits.

32

A UDP header contains ____ number of fields?

4 - sort and destination ports, length and checksum

How many header fields are in a Frame? What are they?

5 - preamble, start frame delimiter, dest and src addr, type field (of payload)

How many flags are in a TCP header?

6 flags, therefore 6 bits (one bit = one flag)

An IP packet cannot exceed ___ bytes.

65,535 bytes

How many fields are in an IPv6 packet header? What are they?

8 - version, traffic class, flow label, payload length, next header, hop limit, source and destination addresses.

A jumbo frame can allow for a max transmission unit of ____ bytes.

9198 bytes

What is an autonomous system?

A group of networks, often in the same domain/trusted network, that are operated by the same organization.

What is administrative distance?

A number indicating the protocol's reliability, with lower numbers being given higher priority.

What is routing cost?

A value assigned to a particular route as judged by the network admin. More desirable paths have low costs.

Dubbed the protocol of the internet, its a hybrid routing protocol for edge and exterior routers (link-state + distance-vector hybrid), uses BGP specific messaging between routers, considers many factors for determining best-path, allows for customization, and its efficient.

BGP

Which of the routing protocols is known as a hybrid routing protocol?

BGP

What are the benefits of IPv6?

Better security, better prioritization provisions, more automatic IP address configurations, and additional IP addresses.

Define BGP.

Border gateway protocol

What are interior routers located within the same autonomous system called?

Core routers

Routing protocols that calculate the best path to a destination on the basis of the distance to that destination.

Distance-vector routing protocols

ICMP type and code fields indicate what?

Error message and error subcategory, respectively.

How does an IPv6 packet identify itself relative to other IPv6 packets?

Flow label - which flow or sequence it belongs to.

The equivalent of TTL on a IPv6 header is called the ___.

Hop Limit

The IP header field that describes the length of the header is called the...

IHL - internet header length

Which protocol enables TCP/IP to internetwork?

IP (internet protocol)

ARP operates at which layer?

Layer 2, although it fetches some layer 3 data for its tables

ICMP operates at what layer?

Layer 3 alongside IP

Introduced as an improvement to RIP, it imposes no hop limits, calculates more efficient best paths, shares link data with other routers, fast convergence, low overhead, prevents routing loops, and is supported by all modern routers.

OSPF

Which is best for large networks, RIPv2 or OSPF?

OSPF because it has no hop limits, whereas RIPv2 has 15 hops max.

Name the two link-state routing protocols.

OSPF, IS-IS

What does OSPF stand for?

Open Shortest Path First

Considered outdated routing protocols but are still used in some cases due to simplicity and compatibility with older routers.

RIP and RIPv2

Name the interior routing protocols discussed.

RIP, RIPv2, OSPF, IS-IS, EIGRP

Name some routing protocols.

RIP, RIPv2, OSPF, IS-IS, EIGRP, BGP.

ICMP mainly does what?

Reports on the success or failure of data delivery. It can indicate network congestion, data failing to reach its destination, discarded packets, and helps with discovering nodes on a network. Ping and traceroute use this.

What are the three flag bits exchanged in the three way handshake?

SYN, ACK SYN, and ACK

What is CSMA/CD?

The name of the original Ethernet standard, which relied on hubs and

Typically, layer 3 switches differ from a core router in that...

They may be faster and less expensive.

Explain TTL.

Time to live is a field in an IP header, counting down the number of hops (router passes) remaining. At zero, it gets discarded and a TTL expired message via ICMP is sent back to the source.

What are the 6 flags in a TCP header?

URG, ACK, PSH, RST, SYN, and FIN

You can manipulate the ARP table with the ___ command.

arp (which takes you to the arp utility in the command line window) (manually places entries are called static)

Layer 3 and 4 switches are best used in...

backbone cabling, not a whole LAN

TCP operates at which OSI layer?

transport

IP itself doesn't rely on connection. T or F?

true

T or F? Distance-vector routing protocols periodically share information with neighboring routers and cannot independently assess network conditions two or more hops away.

true

ICMP headers have ___ fields.

4 - type, code, checksum, and contents vary

What is a routing table?

A list of possible routes. A database that holds information about where hosts are located and the most efficient way to reach them.

Define ARP.

Address Resolution Protocol - protocol for discovering MAC addressed devices on a network, and keeps an ARP table/cache locally, which maps local IP addresses to MAC addresses.

What does BGP stand for?

Border Gateway Protocol

What does CSMA/CD stand for?

Carrier Sense Multiple Access with Collision Detection

Whats the difference between a dynamic arp table entry and a static arp table entry?

Dynamic entries are derived from the broadcast messages being replied to. Static entries are typed manually by the user.

Sometimes referred to as a hybrid protocol, combining distance vector and link-state features, fast convergence, low network overhead, easier to configure and less CPU intensive that OSPF. Also can support multiple protocols and limits unnecessary traffic between routers.

EIGRP

What do you call a router that connects an autonomous system to an outside/untrusted network?

Edge routers, or border routers

What defines the edges of a collision domain?

End device connected directly. If a hub is used, all devices on the hub can have data collisions.

What does EIGRP stand for?

Enhanced Interior Gateway Routing Protocol

What do we call a router outside of our trusted network/AS?

Exterior router

ICMP headers are inserted right after ____.

IP headers

Although the max size of a packet is about 65Kb, a frame is at most, 1.5Kb, including its payload. How does this work?

IP packets too large are fragmented so that they fit the max size of the frame.

In UDP, use of checksums is required for....

IPv6

Designed for core routers only, uses a best-path algorithm, ISPs prefer it, and it easily adapts for IPv6.

IS-IS

What are routing metrics?

Information about each route that defines a number. The smaller the number, the more efficient the route. It's a tie breaker for multiple possible paths.

What is the DiffServ field in IPv4 packet headers?

Informs routers the level of precedence they should apply for the packet.

What are IGPs?

Interior gateway protocols, which only operate within an autonomous system.

What does IS-IS stand for?

Intermediate System to Intermediate System

____ enable routers to communicate beyond neighboring routers, after which each router can independently map the network and determine the best path between itself and a message's destination node.

Link-state routing protocols

MTU means what?

Maximum transmission unit - the largest size in bytes that routers in a message's path will allow at the Network layer. Typically, this results in frames at layer 2 to be at most 1500 bytes.

What is wireshark?

Protocol analyzer, packet sniffer, packet analyzer.

____ only considers the number of hops between nodes when determining the best path.

RIP

Name three distance-vector routing protocols.

RIP, RIPv2, and EIGRP.

In TCP headers, the acknowledgement number field contains the previous data's ____

Sequence number, plus 1

What are the transport layer protocols?

TCP and UDP

What is a default route?

The last route in the routing table, located at IP address 0.0.0.0. It's the route a router will choose if no other entry on the routing table is a match for that destination. It will send the data to its gateway of last resort.

What is a gateway of last resort?

The router that accepts unroutable messages from other routers.

What is convergence time?

The time between losing the route and finding a working replacement route

DNS uses what layer 4 protocol?

UDP

ARPing asks what?

Will this IP address send me it's MAC address?

The TCP header contains a string of characters ued to verify message integrity, it is called a ...

checksum

Layer 4 switches are also called...

content/application switches

What does the netstat utility show?

current network connections, port numbers used on them, messages handled and number of data errors on a NIC

___ are routing protocols used by edge routers and exterior routers to distribute data outside of autonomous systems. In other words, protocols that route information between autonomous systems.

exterior gateway protocols

Layer 4 switch capabilities include...

filtering data, keep statistics, and security functions

What is the term for when a TCP segment/datagram wants to slow down or speed up the transmission of data?

flow control

The flags in the IP header deal with what?

fragmentation

What does the Identification field in an IP packet mean?

identifies the message fragment to help with reassembly

In TCP, what is an ISN?

initial sequence number - the first sequence number in the three way handshake

Is there any payload during the three way handshake?

no

Contains filler bits to ensure that the size of the TCP header is a multiple of 32 bits.

padding bits

What does an urgent pointer field indicate in a TCP header?

points to a location in the data that is considered urgent

To view the routing table use what commands?

route on Linux, route print on windows, show ip route on Cisco IOS

What defines the edges of a broadcast domain?

routers, aka the broadcast domain is the entire LAN

Used to determine the best path by a router.

routing protocols

Draw the three way handshake and its three affected fields.

see page 178

TCP headers contain a ___ that determines the order of reassembling the segment/datagram

sequence number

Packets come in two types:

tcp segments and udp datagrams

What field in a TCP header determines flow control?

the "sliding-window size" field

These bits are TCP header bits reserved for special other information

the 32 bit "Options" field

What TCP flag indicates the end of a transmission?

the FIN flag

TCP sets up a connection, by steps called the...

three-way handshake

Which command uses ICMP echo requests to trace the path from one networked node to another, identifying all intermediate hops between the two nodes?

tracert (Windows) or traceroute (Linux)

Priority handling in IPv6 is done with the ___ header field.

traffic class