Lucent Technologies PortMaster Netmasks

Networking Concepts A-7

Network Addressing

Netmasks

A netmask is a four-octet number that identifies either a supernetwork (supernet) or a

subnetwork (subnet). A netmask that designates a subnet is called a subnet mask.

Using Subnet Masks to Create IP Subnets

Subnet masks are used to divide networks into smaller, more manageable groups of

hosts known as subnets. Subnetting is a scheme for imposing a hierarchy on hosts on a

single physical network. The usual practice is to use the first few bits in the host portion

of the network address for a subnet field. RFC 950, Internet Stand ard Subnetting Procedure,

describes subnetting.

A subnet mask identifies the subnet field of a network address. This mask is a 32- bit

number written in dotted decimal notation with all 1s (ones) in the network and subnet

portions of the address, and all 0s (zeros) in the host portion. This scheme allows for the

identification of the host portion of any address on the network.

Table A-3 shows the subnet masks you can use to divide a class C network into subnets.

Table A-3 Su bnet Masks for a Class C Network

Length

(Subnet

Bits)

Number of

Subnets

Number of

Hosts per

Subnet

Hexadecimal

Subnet Mask

Dotted Decimal

Subnet Mask

24 1 254 0xffffff00 2 55.255.255.0

25 2 126 0xffffff80 2 55.255.255.128

26 4 62 0x ffffffc0 255.255.255.192

27 8 30 0x ffffffe0 255.255.255.224

28 16 14 0x fffffff0 255.255.255.240

29 32 6 0x fffffff8 255.255.255.248

30 64 2 0x fffffffc 255.255.255.252

32 256 1 0xffffffff 255.2 55.255.255

Contents

Main PortMaster Configuration Guide Page Contents Page Page Page Page Page Page Page Page Page Page Page Page Page About This Guide Audience PortMaster Documentation Page Additional References RFCs Page ITU-T Recommendations Books Document Conventions Document Advisories Contacting Lucent Remote Access Technical Support For the EMEA Region For North America, Latin America, and the Asia Pacific Region PortMaster Training Courses Subscribing to PortMaster Mailing Lists Page Introduction 1 PortMaster Software Preconfiguration Planning Configuration Tips Basic Configuration Steps Page Page How the PortMaster Works 2 Booting the PortMaster Page PortMaster Initialization On-Demand Connections PortMaster Security Management Port Status and Configuration Page Configuring Global Settings 3 Setting the System Name Setting the Administrative Password Setting the Dynamic Host Control Protocol (DHCP) Server How the Cable Modem Telephone Return System Works Setting the Dynamic Host Control Protocol (DHCP) Server 3-4 PortMaster Configuration Guide Figure 3-1 Cable Modem Telephone Return Interface Startup PM3 Setting the Default Route Gateway Configuring Default Routing Configuring Name Resolution Using the Host Table Setting the Name Service Setting the Name Server Setting the Domain Name Setting the Telnet Port Using the Telnet Port as a Console Port Setting the Number of Management Application Connections Setting System Logging Setting the Loghost Disabling and Redirecting Syslog Messages Page Setting Administrative Logins to Serial Ports Configuring an IP Address Pool Setting the Reported IP Address Configuring SNMP About the livingston.mib Definition File Examining the MIB Structure Configuring Global Settings 3-15 Configuring SNMP Figure 3-2 Manage ment Information Base (MIB) Hierarchy Page PortMaster Serial Interfaces Page PortMaster T1/E1 Interfaces PortMaster Modem Table Setting SNMP Monitoring Setting SNMP Read and Write Community Strings Adding SNMP Read and Write Hosts Viewing SNMP Settings Monitoring SNMP Alarms Displaying the Routing Table Setting Static Routes Adding and Deleting a Static Route for IP Adding and Deleting a Static Route for IPX Modifying the Static Netmask Table Uses for Static Netmasks Example of Applying Static Netmasks Enabling NetBIOS Broadcast Packet Propagation Setting Authentication for Dial-In Users Setting Call-Check Authentication Setting the ISDN Switch Configuring the Ethernet Interface 4 Setting General Ethernet Parameters Applying Filters Input Filters Output Filters Setting IP Parameters Setting the IP Address Setting the Subnet Mask Setting the Broadcast Address Enabling or Disabling IP Traffic Setting Ethernet IPX Parameters Setting the IPX Network Address Enabling or Disabling IPX Traffic Setting the IPX Frame Type Configuring Ethernet Subinterfaces Setting OSPF on the Ethernet Interface Configuring an Asynchronous Port 5 Asynchronous Port Uses Page General Asynchronous Port Settings Overriding Certain Port Settings Setting the Port Speed Parity Checking Setting Databits T Setting Flow Control Setting the Dial Group Displaying Extended Port Information Setting the Login Prompt Setting the Login Message Setting an Optional Access Filter Setting Port Security Allowing Users to Connect Directly to a Host Setting a Port as the Console Setting the Port Idle Timer Configuring a PortMaster for Login Users Setting the Port Type Setting the Login Service Setting the Login Host Setting the Terminal Type Configuring a Port for Access to Shared Devices X Page Setting the Device Service PortMaster Device Service Telnet Device Service Netdata Device Service Configuring a Port for Network Access Network Dial-In-Only Access Network Dial-Out-Only Access Network Dial-In-and-Out (Two-Way) Access PPP and SLIP Connections PAP and CHAP Authentication Configuring a Port for a Dedicated Connection Page Setting the Destination IP Address and Netmask Configuring Compression Setting the PPP Asynchronous Map Setting Input and Output Filters Connecting without TCP/IP Support Page Configuring a Synchronous WAN Port 6 Synchronous Port Uses Page Page Configuring WAN Port Settings General Synchronous Settings Displaying Extended Port Information Setting the Port Type and Connection Type Setting the Port Speed Reference Setting Modem Control Assigning a Port to a Dial Group Setting Hangup Control Setting the Port Idle Timer Settings for Hardwired Connections Setting the Transport Protocol Setting the Port IP Address Setting the Destination IP Address Setting the Subnet Mask Setting the IPX Network Address Configuring RIP Routing Setting Input and Output Filters Setting Compression Page Configuring Dial-In Users 7 Configuring the User Table Displaying User Information Adding Users to the User Table Deleting Users from the User Table User Types Network Users Login Users Page Setting the User IP Address Setting the Subnet Mask Setting the Asynchronous Character Map Setting the Maximum Number of Dial-In Ports Setting Compression Setting Filters Specifying a Callback Location Configuring Login Users Setting the Login Host Applying an Optional Access Filter Setting the Login Service Type Specifying a Callback Telephone Number Page Configuring Dial-Out Connections 8 Configuring the Location Table Page Creating a Location Setting the Connection Type On-Demand Continuous Manual Dial-Out Setting the Telephone Number Setting the Username and Password Setting the Protocol Setting the Destination IP Address Setting the Destination Netmask Setting RIP Routing Setting the Dial Group Configuring Compression Page Setting the Idle Timer Setting Data over Voice Setting CHAP Setting the Asynchronous Character Map Setting Multiline Load Balancing Setting the Maximum Number of Dial-Out Ports Setting Bandwidth-on-Demand Setting Filters Input Filters Output Filters Testing Your Location Configuration Configuring Filters 9 Overview of PortMaster Filtering Filter Options Filter Organization How Filters Work Creating Filters Creating IP Filters Filtering ICMP Packets Filtering TCP and UDP Packets TCP Packets UDP Packets Creating IPX Filters Creating SAP Filters Displaying Filters Deleting Filters Example Filters Simple Filter Input Filter for an Internet Connection Input and Output Filters for FTP Packets Rule to Permit DNS into Your Local Network Rule to Listen to RIP Information Rule to Allow Authentication Queries Rule to Allow Networks Full Access Restrictive Internet Filter Page Restricting User Access Page Using Modems 10 Null Modem Cable and Signals Modem Functions Using Automatic Modem Configuration Displaying Modem Settings and Status Adding a Modem to the Modem Table Page Page Associating a Modem with a Port Configuring Ports for Modem Use Setting the Port Speed Setting Modem Control Setting Parity Setting the Flow Control Hanging Up a Line Page Configuring the PortMaster 3 11 Configuring General Settings Displaying Line Status Configuring Line Use Setting Channel Groups Setting the Channel Rate Setting the Inband Signaling Protocol for T1 Setting the Inband Signaling Protocol for E1 Configuring ISDN PRI Settings Setting the ISDN PRI Switch Setting the Framing Format Setting the Encoding Method Setting the Pulse Code Modulation Setting the Loopback Setting the Directory Number Using True Digital Modems Setting Digital Modems Hot-Swapping Digital Modem Cards Setting Digital Modems to Analog Service Using Channelized T1 Why Use Channelized T1? How to Order DS-1 Service from the Telephone Company Configuring the PortMaster 3 for Channelized T1 Example Channelized T1 Configuration Using the T1 Expansion Card Clocking Configuring the T1 Expansion Card for Fractional T1 Configuring the PortMaster 3 for Full T1 Troubleshooting the T1 Expansion Card Using Multichassis PPP Setting Multichassis PPP Displaying Multichassis PPP Addresses Disconnecting a User from a Virtual Port Troubleshooting the PortMaster 3 Using ISDN BRI 12 Overview of ISDN BRI Connections Page Provisioning Configuring ISDN ISDN BRI Switch Types North American ISDN BRI Switch Types International ISDN BRI Switch Types Setting the Switch Type Service Profile Identifier (SPID) for ISDN BRI Terminal Identifier (TID) for ISDN BRI Directory Number Information Elements (IEs) Setting the Number Type Setting the Number Plan Multilink PPP Multiple Subscriber Network for an S/T Interface Port Limits Data over Voice ISDN Port Configuration Tips ISDN BRI Unnumbered IP Configuration Example Configuration Steps S.F. Denver Configuring the PortMaster in Denver S.F. Denver Configuring Ethernet IP Interface Settings Configuring ISDN Port Settings Page Page Configuring the PortMaster in San Francisco Page Configuring ISDN Port Settings Page Page Testing the Setup Troubleshooting an ISDN BRI Connection Interpreting ISDN BRI Port Status Using Frame Relay 13 Overview of Frame Relay PVCs and DLCIs Line Speed Port Speed CIR and Burst Speed Discarding Frames Ordering Frame Relay Service LMI Types Frame Relay Configuration on the PortMaster Enabling LMI Enabling Annex-D Listing DLCIs for Frame Relay Access Configuration Steps for a Frame Relay Connection Configuring the PortMaster in Bangkok Configuring Synchronous WAN Port Parameters Configuring the PortMaster in New York Page Troubleshooting a Frame Relay Configuration Frame Relay Subinterfaces Configuring Subinterfaces Adding a Location Creating a DLCI Entry Displaying DLCI Entries Troubleshooting Subinterfaces Example: Configuring a Frame Relay Subinterface Page Using Synchronous V.25bis Connections 14 Overview of Synchronous V.25bis Dial-Up Connections Page Configuration Steps for a Synchronous V.25bis Connection Configuring the PortMaster in Boston Page Page Page Configuring the PortMaster in Miami Page Page Page Page Testing the Configuration Troubleshooting a Synchronous V.25bis Connection Page Using Office-to-Office Connections 15 Overview of Example Configuration Page Configuration Steps for an Office-to-Office Connection Configuring the Office Router in London Configuring PCMCIA Serial Port Settings Dial-In User Settings for London Dial-Out Location Settings for London Configuring the PortMaster in Paris Configuring Dial-Out Port Settings Page Configuring Dial-Out Location Settings Testing the Setup Setting the Console Port for Multiline Load Balancing Page Using ISDN for On-Demand Connections Page Using Internet Connections 16 Page Overview of Continuous Internet Connections Configuration Steps for an Internet Connection Configuring Port Settings Ethernet Interface Settings Serial Port Settings for Dial-Out Serial Port Settings for a Hardwired Connection Configuring a Dial-Out Location Testing the Continuous Dial-Out Setup Testing the Network Hardwired Setup Providing Network Filtering Using ISDN for Internet Connections Page Providing User Dial-In Access 17 Overview of Dial-In Configuration Page Example Configuration Configuration Steps for Dial-In Access Connecting Modems Configuring Ports Configuring Ethernet Port Settings Configuring Serial Modem Port Settings Page Configuring Users RADIUS Settings Dial-In Login Users Dial-In Network Users Testing the User Dial-In Setup Page Page Accessing Shared Devices 18 Overview of Shared Device Access Methods Host Device Configuration Network Device Configuration X Page Configuration Steps for Shared Device Access Configuring Port Settings Ethernet Interface Settings Two-Way Serial Port (S2) Settings Page Serial Printer Port (S9) Settings Parallel Port (P0) Settings Configuring a Network Device for Telnet Access Page Page Using Synchronous Leased Lines 19 Overview of Leased Line Connections Page Configuration Steps for Leased Line Connections Configuring the PortMaster Office Router in Rome Page Configuring the PortMaster Office Router in Florence Configuring Synchronous WAN Port Parameters Troubleshooting a Leased Line Connection Page Page Networking Concepts A Network Addressing IP Addressing IP Address Notation IP Address Classes Class A Addresses Class B Addresses Class C Addresses Class D Addresses Class E Addresses Reserved IP Addresses Private IP Networks IP Address Conventions IPX Addressing Netmasks Using Subnet Masks to Create IP Subnets Subnetting, Routing, and VLSMs Using Naming Services and the Host Table Managing Network Security RADIUS ChoiceNet TCP and UDP Ports and Services B Page Page Page Glossary A Page B Page C Page Page D Page Page E F Page G H I Page Page K L Page M Page N Page Page O P Page R Page Page S Page T U V W Command Index A D R S Page Page Page Page Page Subject Index A B C D E F G H I K L M N O P R S T U V W