Microsoft PowerPoint - Ch04a.pptIntroduction IP Address & MAC
Address TCP/UDP/ICMP IP Gateway, Network Mask, TTL Routing Protocol
Network Address Translation (NAT) Domain Name System (DNS) Dynamic
Host Configuration Protocol (DHCP) / Asymmetric Digital Subscriber
Line (ADSL) HyperText Transfer Protocol (HTTP) Protocol Virtual
Private Network (VPN)
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Gateway
LAN WAN Gateway Internet RouterRouter
TCP/IPX.25Systems Network Architecture (SNA)Gateway Packet (
)
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SNA IBM
PC1GatewayARP Gateway MAC Address PC1 NetmaskIP Gateway
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PC 1 Windows2000
1. arp –a 2. ping 168.95.1.1 3. arp –a 4. route print
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Routing Table
Router Packet Packet IPDestination IP Address Packet
Routing Table
Routing Table Layer 3 PCFirewallRouter PDA
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Linux Host Routing Table (ip route)
Linux Host Routing Table /sbin/ip route (mask bit)
/sbin/route
[root@gr /]# /sbin/ip route
61.218.155.224/28 dev eth1 scope link src 61.218.155.226
192.168.2.0/24 dev eth0 scope link src 192.168.2.254 192.168.0.0/24
dev eth0 scope link src 192.168.0.10 192.168.254.0/24 dev eth0
scope link src 192.168.254.254 10.0.0.0/16 dev eth0 scope link src
10.0.0.10 172.16.0.0/16 dev eth0 scope link src 172.16.0.10
127.0.0.0/8 dev lo scope link default via 61.218.155.225 dev
eth1
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Kernel IP routing table Destination Gateway Genmask Metric Iface
NAT 61.218.155.224 * 255.255.255.240 0 eth1 192.168.2.0 *
255.255.255.0 0 eth0 192.168.0.0 * 255.255.255.0 0 eth0
192.168.254.0 * 255.255.255.0 0 eth0 10.0.0.0 * 255.255.0.0 0 eth1
172.16.0.0 * 255.255.0.0 0 eth0 127.0.0.0 * 255.0.0.0 0 lo default
61.218.155.225 0.0.0.0 0 eth1
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Default0.0.0.0 / 00.0.0.0 / 0 IP Entry Packet
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Packet Destination IP 61.218.155.236 Entry 61.218.155.224/28 28
bits
IP 00111101 11011010 10011011 1110 1100
IP 61.218.155.236 Routing Table entry
Longest Prefix Length Match
√
√
√
Routing Table Entry
Routing Table Entry Routing Decision IP 28 bits 61.218.155.224 28
bits eth1
scope link IP Destination MAC ARP src 61.218.155.226 eth1 IP
61.218.155.226 1,2,5 Entry 1 match 28 bits Entry 1 eth1
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TCP/IProuting protocol Routing Information Protocol (RIP), Open
Shortest Path First (OSPF), Border Gateway Protocol (BGP) (Chapter
5)
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Routing
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Slow Path: CPURouting Protocol
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Router Routing Table Packet Packet
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Application Gateway
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Routing Table Default GatewayDefault Gateway Packet
ADSLADSL ATU-R Default Gateway
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Default Gateway
ISP Default Gateway ADSL Default Gateway DHCP (Dynamic Host
Configuration Protocol, RFC 1541, RFC 2131) Default GatewayCable
Modem PPP (The Point-to-Point Protocol, RFC 1661) Default Gateway
Modem ADSLPPPoE (PPP over Ethernet) ( PPP)
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PPPoEDefault Gateway
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PC1PPPoE
PPP IPGatewayDNS Routing TableDefault Gateway PPP Gateway IP
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RoutingPacket Intel IXP Network Processor IBM PowerNP Linux
Router
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[1] Linux Router Project, http://www.linuxrouter.org/ [2] Free
Cisco, http://www.freesco.org/ [3] IBM PowerNP, http://www.ibm.com
[4] Intel IXP Network Processor, http://www.intel.com [5] Linux
Routing Protocol, http://www.zebra.org
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Linux PC 1 PC 4 HTTP
Hub PC1PC4
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NetGuru
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ifconfig eth0 192.168.0.1 netmask 255.255.255.0 ip route add
default via 192.168.0.254
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IP Network Mask ifconfig Route Entry
192.168.0.0/24 dev eth0 scope link src 192.168.1.254
ip route add 192.168.1.254/24 dev eth0
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eth1 IP Network Mask ifconfig Route Entry
192.168.2.0/24 dev eth2 scope link src 192.168.2.254
ip route add 192.168.2.254/24 dev eth2
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ifconfig eth2 192.168.2.3 netmask 255.255.255.0 ip route add
default via 192.168.2.254
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Proxy
WEB Proxy Proxy Proxy Server WEB Proxy squid
http://www.squid-cache.org/
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Proxy ARPARP ARPProxy ARP() MAC Address Proxy ARP
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PC 1 PC 4 Proxy ARP
PC 4 MAC Address Linux eth0 MAC AddressPC 4 ARP Request PC 1 MAC
Address Linux eth2
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NetGuru
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NetGuru
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NetGuru Host B Proxy ARP
arp –i eth1 –Ds 192.168.1.1 eth1 netmask 255.255.255.255 pub arp –i
eth0 –Ds 192.168.1.10 eth0 netmask 255.255.255.255 pub
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Host B: ifconfig eth1 down
Host C: ifconfig eth0 down ifconfig eth1 down
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Host A:
default gateway