Foundation Summary 87
Foundation Summary
The “Foundation Summary” is a condensed collection of material for a convenient review of key concepts in this chapter. If you are already comfortable with the topics in this chapter and decided to skip most of the “Foundation Topics” material, the “Foundation Summary” will help you recall a few details. If you just read the “Foundation Topics” section, this review should help further solidify some key facts. If you are doing your final preparation before the exam, the “Foundation Summary” offers a convenient and quick final review.
Table 2-17 OSI Model
OSI Name and Layer |
|
Number |
Description |
|
|
Application layer (Layer 7) |
The application layer is closest to the end user, which means that the |
|
application is being accessed by the end user. This layer’s major function |
|
is to provide services to end users. Examples of application layer |
|
services include the following: |
|
File Transfer Protocol (FTP) |
|
Telnet |
|
Ping |
|
Trace route |
|
SMTP |
|
Mail clients |
|
|
Presentation layer (Layer 6) |
The Presentation layer handles data formats and code formatting. This |
|
layer’s functions are normally transparent to the end user because it takes |
|
care of code formats and presents them to the application layer (Layer 7), |
|
where the end user can examine the data. Examples of presentation layer |
|
protocols include the following: |
|
GIF |
|
JPEG |
|
ASCII |
|
MPEG |
|
TIFF |
|
MIDI |
|
HTML |
|
|
Session layer (Layer 5) |
The session layer performs several major functions, including managing |
|
sessions between devices and establishing and maintaining sessions. |
|
Examples of session layer protocols include the following: |
|
Database SQL |
|
NetBIOS Name Queries |
|
H.323 |
|
Real Time Control Protocol |
|
|
continues
88 Chapter 2: General Networking Topics
Table 2-17 OSI Model (Continued)
OSI Name and Layer |
|
Number |
Description |
|
|
Transport layer (Layer 4) |
The transport layer is responsible for segmenting upper-layer applica- |
|
tions and establishing end-to-end connections between devices. Other |
|
transport layer functions include providing data reliability and error-free |
|
delivery mechanisms. Information being processed at this layer is com- |
|
monly known as segments. Examples of transport layer protocols include |
|
Transmission Control Protocol (TCP) and User Datagram Protocol (UDP). |
|
|
Network layer (Layer 3) |
The network layer determines the best path to a destination. Device |
|
addressing, packet fragmentation, and routing all occur at the network |
|
layer. Information being processed at this layer is commonly known as |
|
packets. Examples of network layer protocols include the following: |
|
Internet Protocol (IP) |
|
Open Shortest Path First (OSPF) |
|
Cisco’s EIGRP routing protocol |
|
|
Data Link layer (Layer 2) |
The data link layer focuses on getting data reliably across any particular |
|
kind of link. Flow control and error notifications are other data link layer |
|
functions. The data link layer applies to all access methods, whether they |
|
are LAN or WAN methods. Information being processed at this layer is |
|
commonly known as frames. Example include the following: |
|
ISDN |
|
SDLC |
|
HDLC |
|
PPP |
|
Frame Relay |
|
Spanning tree protocol |
|
NetBEUI |
|
|
Physical layer (Layer 1) |
The physical layer consists of standards that describe bit ordering, bit |
|
transmission rates, connector types, and electrical and other specifications. |
|
Information at Layer 1 is transmitted in binary (1s and 0s; for example, |
|
the letter A is transmitted as 00001010). Examples of physical layer |
|
standards include the following: |
|
RS-232 |
|
V.24 |
|
V.35 |
|
RJ-45 |
|
RJ-12 |
|
10BaseT |
|
100BaseT |
|
1000BaseT |
|
Gigabit Ethernet |
|
|
Requirements for FastEther Channel 89
Table 2-18 Ethernet Media Formats
Media Type |
Characteristics |
|
|
10Base5 |
Maximum length 500 m. |
|
Maximum stations are 1024. |
|
Speed is 10 Mbps. |
|
Minimum distance between devices is 2.5 m. |
|
|
10Base2 |
Maximum length 185 m, using RG58 cable types, T connectors on all end stations. |
|
Minimum distance between devices is 0.5 m. |
|
Maximum devices per 185 m segment is 30 stations. |
|
Speed is 10 Mbps. |
|
End points need termination. |
|
|
10BaseT |
Based on UTP cabling. |
|
Up to 100 m (longer for better category cables). |
|
One device per cable. |
|
Typically only one device per segment with hubs or switches connecting all devices |
|
together. |
|
Speed is 10 Mbps. |
|
Physical topology is star, logical topology is liner. |
|
|
100BaseT |
Same characteristics as 10baseT but operates faster, at 100 Mbps. Can be fibre, as |
|
well (100BaseFx). Defined in IEEE 802.3U. |
|
|
1000 GE |
Gigabit Ethernet operating at 1000 Mbps. |
|
Can run over Fibre or UTP. |
|
Frame formats and CSMA/CD identical to Ethernet standards. |
|
|
Requirements for FastEther Channel
•All ports part of FEC must be set to the same speed.
•All ports must belong to the same VLAN.
•Duplex must be the same (half or full), not a mixture.
•Up to eight ports can be bundled together.
•To set FastEther channel on a switch, the CatOS syntax is set port channel.
•To set FastEther channel on a router, the IOS syntax is channel-group under the Fast Ethernet interface.
90 Chapter 2: General Networking Topics
Table 2-19 The States of Spanning Tree
Bridge Port State |
Description |
|
|
Disabled |
The port is not participating in spanning tree and is not active. |
|
|
Listening |
The port has received data from the interface and will listen for frames. In |
|
this state, the bridge receives only data but does not forward any frames to |
|
the interface or to other ports. |
|
|
Learning |
In this state, the bridge still discards incoming frames. The source address |
|
associated with the port is added to the CAM table. BPDU are sent and |
|
received. |
|
|
Forwarding |
The port is fully operational; frames are sent and received. |
|
|
Blocking |
The port has been through the learning and listening states, and because this |
|
particular port is a dual path to the root bridge, the port is blocked to |
|
maintain a loop-free topology. |
|
|
Table 2-20 Class A, B, C, D, and E Ranges
Class of Address |
Starting Bit Pattern |
Range |
Default Subnet Mask |
|
|
|
|
Class A |
0xxxxxxx |
1 to 126, 127* |
255.0.0.0 |
|
|
|
|
Class B |
10xxxxxx |
128 to 191 |
255.255.0.0 |
|
|
|
|
Class C |
110xxxxx |
192 to 223 |
255.255.255.0 |
|
|
|
|
Class D (multicast) |
1110xxxx |
224 to 239 |
255.255.255.240 |
|
|
|
|
Class E |
1111xxxx |
240 to 255 |
Reserved |
|
|
|
|
*127.0.0.0 is reserved for loopbacks. Other reserved addresses for private use as defined by RFC 1918 are as follows: 10.0.0.0-10.255.255.255 172.16.0.0-172.31.255.255 192.168.0.0-192.168.255.255
Table 2-21 Routing Protocol Classifications
Routing Protocol |
Class |
|
|
IGRP |
Distance vector (classful) |
|
|
EIGRP |
Hybrid (classless) |
|
|
OSPF |
Link-state (classless) |
|
|
RIPv1 |
Distance vector (classful) |
|
|
RIPv2 |
Distance vector (classless) |
|
|
BGP |
Path vector (classless) |
|
|
|
|
Requirements for FastEther Channel 91 |
|
|
|
Table 2-22 TCP Flags Summary |
||
|
|
|
|
Flag |
Description |
|
|
|
|
URG (U) |
Urgent—Informs the other station that urgent data is being carried. The receiver will |
|
|
decide what do with the data. |
|
|
|
|
ACK (A) |
Acknowledge—Indicates that the packet is an acknowledgment of received data, and |
|
|
the acknowledgment number is valid. |
|
|
|
|
PSH (P) |
Push—Informs the end station to send data to the application layer immediately. |
|
|
|
|
RST (R) |
Reset—Resets an existing connection. |
|
|
|
|
SYN (S) |
Synchronize—Initiates a connection, commonly known as established. |
|
|
|
|
FIN (F) |
Finished—Indicates that the sender is finished sending data and terminates the session. |
|
|
|
Table 2-23 TCP/IP Applications
Application |
Description |
|
|
Address Resolution Protocol (ARP) |
ARP maps an IP address to a MAC address. |
|
|
Reverse Address Resolution Protocol (RARP) |
RARP determines a host’s IP address when the MAC |
|
address is known. |
|
|
Dynamic Host Configuration Protocol (DHCP) |
Dynamically provides IP addresses to TCP/IP hosts, |
|
subnet masks, and gateway addressing. Many other |
|
IP options can be assigned, as well. |
|
|
Hot Standby Router Protocol (HSRP) |
Redundancy gateway protocol, Cisco proprietary. |
|
|
Internet Control Message Protocol (ICMP) |
A network layer (Layer 3) Internet protocol that |
|
reports errors and provides other information |
|
relevant to IP packet processing. ICMP is fully |
|
documented in RFC 792. |
|
|
Telnet |
TCP/IP application layer protocol that enables |
|
remote management of TCP/IP hosts, such as routers |
|
or switches. |
|
|
File Transfer Protocol (FTP) |
TCP/IP application layer protocol that enables file |
|
transfer between TCP/IP hosts using a TCP, |
|
connection-orientated protocol. |
|
|
Trivial File Transfer Protocol (TFTP) |
TCP/IP application layer protocol that enables file |
|
transfers between TCP/IP hosts using a UDP, |
|
connectionless protocol. |
|
|
92 Chapter 2: General Networking Topics
Table 2-24 Default Administrative Distances
Route Source |
Default Distance |
|
|
Connected interface |
0 |
|
|
Static route |
1 |
|
|
Enhanced IGRP summary route |
5 |
|
|
External BGP |
20 |
|
|
Internal enhanced IGRP |
90 |
|
|
IGRP |
100 |
|
|
OSPF |
110 |
|
|
IS-IS |
115 |
|
|
RIP |
120 |
|
|
EGP |
140 |
|
|
EIGRP external route |
170 |
|
|
Internal BGP |
200 |
|
|
Unknown |
255 |
|
|
Q & A 93
Q & A
The Q & A questions are designed to help you assess your readiness for the topics covered on the CCIE Security written exam and those topics presented in this chapter. This format helps you assess your retention of the material. A strong understanding of the answers to
these questions will help you on the CCIE Security written exam. You can also look over the questions at the beginning of the chapter again for further review. As an additional study aid, use the CD-ROM provided with this book to take simulated exams, which draw from a database of over 300 multiple-choice questions—all different from those presented in the book.
Select the best answer. Answers to these questions can be found in Appendix A, “Answers to Quiz Questions.”
1What are the seven layers of the OSI model?
2What layer of the OSI model is responsible for ensuring that IP packets are routed from one location to another?
3What mechanism is used in Ethernet to guarantee packet delivery over the wire?
4Name two physical characteristics of 10BaseT?
94 Chapter 2: General Networking Topics
5What Catalyst command displays the bridging or CAM table on a Cisco 5000 series switch?
6What are the possible states of spanning tree?
7FastEther Channel (FEC) allows what to occur between Cisco Catalyst switches?
8What field in the IP packet guarantees data delivery?
9Name some examples of connection-orientated protocols used in TCP/IP networks.
10Given the address, 131.108.1.56/24, what are the subnet and broadcast addresses? How many hosts can reside on this network?
11How many hosts can reside when the subnet mask applied to the network 131.108.1.0 is 255.255.255.128 (or 131.108.1.0/25)?
Q & A 95
12Name five routing protocols that support VLSM.
13What is the destination port number used in a Telnet session?
14What TCP/IP services are common in today’s large IP networks?
15What IOS command displays the IP ARP table on a Cisco IOS router?
16Cisco routers use what mechanism to determine the routing selection policy for remote networks if more than one routing protocol is running?
17What is the administrative distance for OSPF, RIP, and external EIGRP?
18Name five characteristics of distance vector routing protocols and provide two examples of routing protocols classified as distance vector.
96 Chapter 2: General Networking Topics
19IP RIP runs over what protocol and port number when sending packets to neighboring routers?
20How many networks can be contained in an IP RIP update?
21Specify three main differences between RIPv1 and RIPv2?
22What is an EIGRP Feasible Successor?
23What is the metric used by OSPF?
24If OSPF is configured for one area, what area assignment should be used?
25What LSA types are not sent in a total stubby area?
Q & A 97
26What IOS command disables an interface from participating in the election of an OSPF DR/BDR router?
27On an Ethernet broadcast network, a DR suddenly reboots. When the router recovers and discovers neighboring OSPF routers, will it be the designated router once more?
28What Layer 4 protocol does BGP use to guarantee routing updates, and what destination port number is used?
29What are ISDN BRI and PRI?
30What are the three phases that occur in any PPP session?
31Define what BECN and FECN mean in a Frame Relay network?
98 Chapter 2: General Networking Topics
32Frame Relay DLCI values are used for what purpose?
33What is the IP address range used in IP multicast networks?
34What type of network environment typically uses an AS5300?