331
10.3.4.
Router
Routers, operating at the OSI Network layer, organize the large network in terms of logical network segments. Each network seg-
ment is assigned an address so that every packet has both a destination network address and a destination device address.
Routers are more intelligent than bridges. Not only do routers build tables of network locations, but they also use algorithms to
determine the most efficient path for sending a packet to any given network by identifying its header information.
These are the typical functions:
1. Routing
This controls the traffic according to a specified routing table.
2. Packet Filtering
This performs the access and security control for specified routing.
3. Address conversion
NAT (Network Address Translator), This performs conversion of a single global IP Address from/to single private IP Address.
4. IP Masquerade:
This performs a conversion of single global IP Address from/to multiple private IP Address.
At the same time the port number is automatically assigned.
Occasionally, the conversion creates a bottleneck in the network overhead. For a typical solution, PIX
(Private address Internet address exchange) is available from Cisco, which is a well-known manufacturer.
5. Designated replys
These are replys that keep a connection alive by responding with a signal periodically.
Watch Dog in IPX/SPX, TCP/IP in TCP, and Net BT (NetBIOS on TCP/IP) in Windows NT are all well
known techniques to keep a live connection.
PC-A
192.168.32.1/24
Router B
PC-B
192.168.32.2/24
PC-C
192.168.33.1/24
PC-D
192.168.33.2/24
access-list permit tcp 192.168.32.0 0.0.0.255 192.168.33.1 0.0.0.0 eq 23
OK
OK
permission denied
permission denied
192.168.32/24
192.168.33/24
Packet Filtering Sample
Summary of Contents for Panafax DX-2000
Page 2: ......
Page 27: ...27 9 1 Screw 19 10 Release two Latch Hooks 11 Remove the SNS Assembly 121 9 10 11 ...
Page 49: ...49 2 15 Screw Identification Template ...
Page 57: ...57 3 7 3 Option Cassette Circuit 555 748 728 744 928 953 730 731 731 952 944 930 931 931 ...
Page 58: ...58 3 7 4 LAN Control Circuit 522 CN50 1102 1104 1101 N C N C RD N C N C RD TD TD ...
Page 59: ...59 3 7 5 Page Description Language Printer Interface Kit ...