第 6 章 网络层
DESCRIPTION
第 6 章 网络层. 主要内容. 6.1 网络层功能概述( 理解 ) 6.2 数据交换方式 ( 重点、难点 ) 6.3 流量控制和拥塞控制( 难点 ) 6.4 网络层的设备( 重点 ) 6.5 TCP/IP 的网络层 ( 重点、难点 ) 6.6 路由与路由协议 ( 重点、难点 ) 6.7 下一代的网际协议 IPv6. 6.1 网络层功能概述. 主机 A. 主机 B. 应用层. 应用层. 表示层. 表示层. 会话层. 会话层. 传输层. 传输层. 网络层. 网络层. 网络层. 网络层. 网络层. - PowerPoint PPT PresentationTRANSCRIPT
6
R1
R2
R3
H1
H2
R1
R2
R3
H1
H2
1.
(Routing)
H1
H5
H2
H4
H3
A
C
D
B
H6
E
H1
H5
H2
H4
H3
A
C
D
B
H6
E
AB
(
(
(
(
(
(
(
(
6.4
2
3
2. Frame RelayX.25
3. ATMAsynchronous Transfer Mode ATM53
3
2. IP
0
4
8
16
19
24
31
0
1
2
3
4
5
6
7
D
T
R
C
0
1
2
3
4
5
6
7
D
T
R
C
0
1
2
3
4
5
6
7
D
T
R
C
0
1
2
3
4
5
6
7
D
T
R
C
IP 4 ( IPv4)
0
4
8
16
19
24
31
0
1
2
3
4
5
6
7
D
T
R
C
—— 4 bit 15 ( 4 ) IP 60
0
4
8
16
19
24
31
0
1
2
3
4
5
6
7
D
T
R
C
0
4
8
16
19
24
31
0
1
2
3
4
5
6
7
D
T
R
C
65535
0
1
2
3
4
5
6
7
D
T
R
C
0
1
2
3
4
5
6
7
D
T
R
C
0
4
8
16
19
24
31
0
1
2
3
4
5
6
7
D
T
R
C
0
1
2
3
4
5
6
7
D
T
R
C
0
1
2
3
4
5
6
7
D
T
R
C
0
1
2
3
4
5
6
7
D
T
R
C
0
1
2
3
4
5
6
7
D
T
R
C
HA1
HA5
HA4
HA3
HA6
IP1 → IP2
IP1 → IP2
IP1 → IP2
IP1→IP2 IP1 IP2
IP IP
IP1 → IP2
IP1 → IP2
IP1 → IP2
IP1 → IP2
IP1 → IP2
IP1 → IP2
IP ICANN (Internet Corporation for Assigned Names and Numbers)
[RFC 950] 1985
1993
IP
::= “”
1 1 1 1 0
0
1
host-id
1 1 1 1 0
0
1
host-id
1 1 1 1 0
0
1
host-id
1 1 1 1 0
0
1
host-id
1 1 1 1 0
0
1
host-id
1 1 1 1 0
0
1
host-id
1 1 1 1 0
0
1
host-id
1 1 1 1 0
0
1
1 1 1 1 0
0
1
6.2 ABC
B 16,384 (214) 128.0 191.255 65,534
C 2,097,152 (221) 192.0.0 223.255.255 254
0
A
B
C
D
E
1.0.0.0
126.255.255.255
128.0.0.0
191.255.255.255
192.0.0.0
223.255.255.255
224.0.0.0
239.255.255.255
240.0.0.0
246.255.255.255
IP net-id (multihomed host)
IP IP
B
222.1.1.
222.1.1.1
222.1.1.2
222.1.1.3
222.1.1.4
R1
222.1.2.5
222.1.2.2
222.1.2.1
222.1.2.3
222.1.2.4
222.1.2.
222.1.6.1
222.1.5.1
222.1.5.2
222.1.6.2
222.1.4.1
222.1.4.2
222.1.3.3
222.1.3.2
222.1.3.1
R3
R2
222.1.3.
LAN3
N3
N2
222.1.4.
222.1.5.
222.1.6.
N1
LAN2
LAN1
IP IP “” IP
2
00000000000000000000000000000000
10.0.0.0-10.255.255.25510/8
172.16.0.0-172.31.255.255172.16/12)
subnet-id
1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1
0 0 0 0 0 0 0 0
AND
net-id
host-id
subnet-id
1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1
0 0 0 0 0 0 0 0
net-id
subnet-id
net-id
net-id
net-id
A
255.0.0.0
B
255.255.0.0
C
255.255.255.0
1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
1 1 1 1 1 1 1 1
0 0 0 0 0 0 0 0
host-id 0
host-id 0
VLSMVariable Length Subnet MaskingVLSM
Classless Routing ProtocolOSPFRIPv2EIGRPVLSM
VLSM CIDR (Classless Inter-Domain Routing)
CIDR
CIDR A B C IPv4
CIDR“”(network-prefix)
CIDR IP “CIDR”
128.14.32.0
(supernetting)
/20 20 1 1
10.0.0.0/10 IP 10.0.0.0 255.192.0.0
11111111 11000000 00000000 00000000
10.0.0.0/10 IP 10.0.0.0 255.192.0.0
11111111 11000000 00000000 00000000
00001010 00* * * IP
C
206.0.71.128/26
206.0.71.192/26
206.0.68.0/25
206.0.68.128/25
206.0.69.0/25
206.0.69.128/25
206.0.70.0/26
206.0.70.64/26
206.0.70.128/26
206.0.70.192/26
206.0.70.0/24
206.0.71.0/25
206.0.71.0/26
206.0.71.64/26
206.0.71.128/25
206.0.68.0/23
ISP 64 C CIDR ISP 64 1 206.0.64.0/18 ISP
IP
P81
Internet
PC2
PC1
IP:192.168.0.1
Port:3000
ARP (ARP cache) IP
A B IP ARP B IP MAC MAC
ARP
32IP
48MAC
ARPInternet
A
Y
X
B
Z
ARP
ARP
A ARP IP ARP
B A ARP A B ARP B A
ARP
1.1.1.1
1.1.1.2
Purpose: This figure explains how RARP works.
In layer 1, the host on the left needs its IP address. It sends a RARP request with its MAC address.
RARP
Layer 2 of 4:
In layer 2, the host on the right, functioning as a RARP server, maps the MAC address to an IP address.
RARP
ICMPICMPICMPIP“Ping”“Tracert”ICMP
8
16
31
4; 5.
2. ICMP
4Ping
2. Ping
Ping32B“-l Size”“ping 11.8.11.112 –l 1560”
Ping
Ping
4.Ping
Tracert
13.2.4 2tracert
Tracert
tracert [-d] [-h MaximumHops] [-j HostList] [-w Timeout] [-R] [-S SrcAddr] [-4][-6] TargetName
13.2.4 2tracert
3ARPIPPCBIPMACPCAMACMACPCBMACIP
ARPPCAPCBIPMACPCBPCAIPMACPCBPCAPCBARP
A:reply from 10.2.3.3:bytes=32 time<10 ms ttl=128
B:reply from 10.2.2.2:bytes=32 time<10 ms ttl=128
“ARP -a”PC
3A
A255.255.255.0
“ARP -d”ARPA“ping”BA“destination host unreachable”(
“ARP -a”
Bping AB“Request timed out”(“ARP -a”PC
1
1
1
(forwarding table)
“”“”
A
B
2
3
4
P12
Mbps,
LCD
NE40EMPLS VPN PE
NE5000ENE80ENE40EPEASBR
IP
NE40
NE40E
NE80ECN2
MPLSQoS
(5)
2CPU6.15
ASIC
ASICASICASIC
2A :AaIP
routerconfig#ip router prefix mask {address | interface} [distance] [tag tag] [permanent
1 0.0.0.0
0.0.0.0/0IP
{adderss|interface}
routerconfig#ip default-network ip-network-number
3
reliability
cost
IGRPRIP
l IGRP
l IGRPVLSM
IGRPsplit horizonpoison reversetrigger updateholddown timer
OSPFInterior Gateway ProtocolIGPAS
0
4
16
31
0
4
16
31
0
4
16
31
(payload length)—— 16 bit IPv6 64 KB
0
4
16
31
0
4
16
31
0
4
16
31
2
3(Routing)
5 (Authentication)
IANAIPv6
1.IPv6
IPv6
IPv4IPv6IPv6 x:x:x:x:x:x:d.d.d.d“x”IPv696“d”32“IPv4IPv6”“IPv4IPv6”
0:0:0:0:0:0:10.1.2.3::10.11.3.123
fec0:0:0:1::1234/64
1IPv4IPv6
IPv6IPv4IPv6IPv6IPv632IPv4“IPv4IPv6” ::192.168.0.1
3
IPv6 RFC 2374 IPv6 ::ffff:192.168.0.1
“FF”
“”“000T”“T”
“”“1”“2”“ ID”
8
4
4
112
11111111
ID
1Multicast Listener DiscoveryMLD
2Neighbor DiscoveryND
(2
l 80
l
(2)
(4)
R1
R2
R3
H1
H2
R1
R2
R3
H1
H2
1.
(Routing)
H1
H5
H2
H4
H3
A
C
D
B
H6
E
H1
H5
H2
H4
H3
A
C
D
B
H6
E
AB
(
(
(
(
(
(
(
(
6.4
2
3
2. Frame RelayX.25
3. ATMAsynchronous Transfer Mode ATM53
3
2. IP
0
4
8
16
19
24
31
0
1
2
3
4
5
6
7
D
T
R
C
0
1
2
3
4
5
6
7
D
T
R
C
0
1
2
3
4
5
6
7
D
T
R
C
0
1
2
3
4
5
6
7
D
T
R
C
IP 4 ( IPv4)
0
4
8
16
19
24
31
0
1
2
3
4
5
6
7
D
T
R
C
—— 4 bit 15 ( 4 ) IP 60
0
4
8
16
19
24
31
0
1
2
3
4
5
6
7
D
T
R
C
0
4
8
16
19
24
31
0
1
2
3
4
5
6
7
D
T
R
C
65535
0
1
2
3
4
5
6
7
D
T
R
C
0
1
2
3
4
5
6
7
D
T
R
C
0
4
8
16
19
24
31
0
1
2
3
4
5
6
7
D
T
R
C
0
1
2
3
4
5
6
7
D
T
R
C
0
1
2
3
4
5
6
7
D
T
R
C
0
1
2
3
4
5
6
7
D
T
R
C
0
1
2
3
4
5
6
7
D
T
R
C
HA1
HA5
HA4
HA3
HA6
IP1 → IP2
IP1 → IP2
IP1 → IP2
IP1→IP2 IP1 IP2
IP IP
IP1 → IP2
IP1 → IP2
IP1 → IP2
IP1 → IP2
IP1 → IP2
IP1 → IP2
IP ICANN (Internet Corporation for Assigned Names and Numbers)
[RFC 950] 1985
1993
IP
::= “”
1 1 1 1 0
0
1
host-id
1 1 1 1 0
0
1
host-id
1 1 1 1 0
0
1
host-id
1 1 1 1 0
0
1
host-id
1 1 1 1 0
0
1
host-id
1 1 1 1 0
0
1
host-id
1 1 1 1 0
0
1
host-id
1 1 1 1 0
0
1
1 1 1 1 0
0
1
6.2 ABC
B 16,384 (214) 128.0 191.255 65,534
C 2,097,152 (221) 192.0.0 223.255.255 254
0
A
B
C
D
E
1.0.0.0
126.255.255.255
128.0.0.0
191.255.255.255
192.0.0.0
223.255.255.255
224.0.0.0
239.255.255.255
240.0.0.0
246.255.255.255
IP net-id (multihomed host)
IP IP
B
222.1.1.
222.1.1.1
222.1.1.2
222.1.1.3
222.1.1.4
R1
222.1.2.5
222.1.2.2
222.1.2.1
222.1.2.3
222.1.2.4
222.1.2.
222.1.6.1
222.1.5.1
222.1.5.2
222.1.6.2
222.1.4.1
222.1.4.2
222.1.3.3
222.1.3.2
222.1.3.1
R3
R2
222.1.3.
LAN3
N3
N2
222.1.4.
222.1.5.
222.1.6.
N1
LAN2
LAN1
IP IP “” IP
2
00000000000000000000000000000000
10.0.0.0-10.255.255.25510/8
172.16.0.0-172.31.255.255172.16/12)
subnet-id
1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1
0 0 0 0 0 0 0 0
AND
net-id
host-id
subnet-id
1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1
0 0 0 0 0 0 0 0
net-id
subnet-id
net-id
net-id
net-id
A
255.0.0.0
B
255.255.0.0
C
255.255.255.0
1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
1 1 1 1 1 1 1 1
0 0 0 0 0 0 0 0
host-id 0
host-id 0
VLSMVariable Length Subnet MaskingVLSM
Classless Routing ProtocolOSPFRIPv2EIGRPVLSM
VLSM CIDR (Classless Inter-Domain Routing)
CIDR
CIDR A B C IPv4
CIDR“”(network-prefix)
CIDR IP “CIDR”
128.14.32.0
(supernetting)
/20 20 1 1
10.0.0.0/10 IP 10.0.0.0 255.192.0.0
11111111 11000000 00000000 00000000
10.0.0.0/10 IP 10.0.0.0 255.192.0.0
11111111 11000000 00000000 00000000
00001010 00* * * IP
C
206.0.71.128/26
206.0.71.192/26
206.0.68.0/25
206.0.68.128/25
206.0.69.0/25
206.0.69.128/25
206.0.70.0/26
206.0.70.64/26
206.0.70.128/26
206.0.70.192/26
206.0.70.0/24
206.0.71.0/25
206.0.71.0/26
206.0.71.64/26
206.0.71.128/25
206.0.68.0/23
ISP 64 C CIDR ISP 64 1 206.0.64.0/18 ISP
IP
P81
Internet
PC2
PC1
IP:192.168.0.1
Port:3000
ARP (ARP cache) IP
A B IP ARP B IP MAC MAC
ARP
32IP
48MAC
ARPInternet
A
Y
X
B
Z
ARP
ARP
A ARP IP ARP
B A ARP A B ARP B A
ARP
1.1.1.1
1.1.1.2
Purpose: This figure explains how RARP works.
In layer 1, the host on the left needs its IP address. It sends a RARP request with its MAC address.
RARP
Layer 2 of 4:
In layer 2, the host on the right, functioning as a RARP server, maps the MAC address to an IP address.
RARP
ICMPICMPICMPIP“Ping”“Tracert”ICMP
8
16
31
4; 5.
2. ICMP
4Ping
2. Ping
Ping32B“-l Size”“ping 11.8.11.112 –l 1560”
Ping
Ping
4.Ping
Tracert
13.2.4 2tracert
Tracert
tracert [-d] [-h MaximumHops] [-j HostList] [-w Timeout] [-R] [-S SrcAddr] [-4][-6] TargetName
13.2.4 2tracert
3ARPIPPCBIPMACPCAMACMACPCBMACIP
ARPPCAPCBIPMACPCBPCAIPMACPCBPCAPCBARP
A:reply from 10.2.3.3:bytes=32 time<10 ms ttl=128
B:reply from 10.2.2.2:bytes=32 time<10 ms ttl=128
“ARP -a”PC
3A
A255.255.255.0
“ARP -d”ARPA“ping”BA“destination host unreachable”(
“ARP -a”
Bping AB“Request timed out”(“ARP -a”PC
1
1
1
(forwarding table)
“”“”
A
B
2
3
4
P12
Mbps,
LCD
NE40EMPLS VPN PE
NE5000ENE80ENE40EPEASBR
IP
NE40
NE40E
NE80ECN2
MPLSQoS
(5)
2CPU6.15
ASIC
ASICASICASIC
2A :AaIP
routerconfig#ip router prefix mask {address | interface} [distance] [tag tag] [permanent
1 0.0.0.0
0.0.0.0/0IP
{adderss|interface}
routerconfig#ip default-network ip-network-number
3
reliability
cost
IGRPRIP
l IGRP
l IGRPVLSM
IGRPsplit horizonpoison reversetrigger updateholddown timer
OSPFInterior Gateway ProtocolIGPAS
0
4
16
31
0
4
16
31
0
4
16
31
(payload length)—— 16 bit IPv6 64 KB
0
4
16
31
0
4
16
31
0
4
16
31
2
3(Routing)
5 (Authentication)
IANAIPv6
1.IPv6
IPv6
IPv4IPv6IPv6 x:x:x:x:x:x:d.d.d.d“x”IPv696“d”32“IPv4IPv6”“IPv4IPv6”
0:0:0:0:0:0:10.1.2.3::10.11.3.123
fec0:0:0:1::1234/64
1IPv4IPv6
IPv6IPv4IPv6IPv6IPv632IPv4“IPv4IPv6” ::192.168.0.1
3
IPv6 RFC 2374 IPv6 ::ffff:192.168.0.1
“FF”
“”“000T”“T”
“”“1”“2”“ ID”
8
4
4
112
11111111
ID
1Multicast Listener DiscoveryMLD
2Neighbor DiscoveryND
(2
l 80
l
(2)
(4)