ELSA Cable manual Examples, Same IP address, this time with another netmask

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Technical basics 53

IP address

Network address

Netmask

the actual information to be transmitted (useful data), the data packet also contains address and control information.

IP addresses are used in IP networks for communications between various devices. In this case, every host has its own unique address by which it can be identified unambiguously. What does an IP address look like? It consists of four bytes separated by dots, making a total of 32 bits. Each of the four bytes can take on values from 0 to 255, e.g. 192.168.130.124.

To be precise, the IP address refers to the interface, and not the host itself. A terminal device with more than one interface (such as a router) has to have an IP address at its disposal for every single interface. This is why ISDN routers from ELSA for example, have an IP address for communication with the hosts in their own network, as well as a second IP address for communication with the “outside world” using the ISDN. In the same way, ELSA cable modems have an IP address for their own network and another IP address for the exchange of data with the cable network.

An IP address contains the address of the network as well as that of the host. The network address is the same for all hosts on one network, whereas the address of the host is exclusive and unique to the network. A router, for example, can have more than one IP address, each one unique to the network.

How then can you differentiate between the part that determines the network and the part that identifies the host? With the netmask. You know what masks are: they cover up one part of something and only allow a different part to be visible. This is exactly how a netmask operates. It is a number which is identical in structure to the IP address, i.e. 32 zeros or ones. The netmask usually starts with ones at the beginning and ends with zeros. The zeros at the end thus cover the part of the IP address which does not belong to the network address.

Examples:

This address...

...in bytes...

...looks like this in bits:

IP address

192.168.120.253

11000000.10101000.01111000.11111101

Netmask

255.255.255.0

11111111.11111111.11111111.00000000

Network address

192.168.120.0

11000000.10101000.01111000.00000000

 

 

 

The same IP address, this time with another netmask:

This address...

...in bytes...

...looks like this in bits:

IP address

192.168.120.253

11000000.10101000.01111000.11111101

Netmask

255.255.0.0

11111111.11111111.00000000.00000000

Network address

192.168.0.0

11000000.10101000.00000000.00000000

 

 

 

You can see from this that an IP address alone is not enough. A host can only be identified unambiguously in combination with a netmask.

ELSA MicroLink Cable

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Contents Manual Sonnenweg ELSA, IncAachen GermanyIntroducing the Elsa MicroLink Cable Thank you for placing your trust in this Elsa productPage Elsa Cable Modem ContentVI Content Setup/SNMP-module Viii Content Introducing the Elsa MicroLink Cable What does the unit look like?Elsa MicroLink Cable Sync Meanings of the specific blink codesThese LEDs show the corresponding network controller status BC D E F GNode or hub? Highlights of the Elsa MicroLink CableFast Internet Cable networkInternet at all times-always online Regional contentMore than just Internet BackboneProxy servers CE and FCC CE conformity and FCC radiation standardIntroducing the Elsa MicroLink Cable Elsa MicroLink Cable Installation and configurationFirst Steps Configuring the Elsa MicroLink CableConfiguration as a bridge Quick Start Quick configurationsPreparations LAN Off you go into the Web with a whole new sensation of speed Configuration as a routerOn the Router tab, enable the IP Router option Configuring fixed IP addresses not using Dhcp TCP/IP installationObtain IP addresses automatically use Dhcp Checking the IP configuration Configuration modes Requirements for inband configurationUser-friendly method inband Start up inband configuration using telnet Starting inband configuration using Elsa LANconfigThis command Means this For instance Configuration commandsSet/se/snmp/admin The Administrator Command to call up a trace follows this syntax How to start a traceWhats happening on the line? Trace OutputsThis is how FirmSafe works New firmware with FirmSafeExamples Elsa LANconfig How to load new softwareTftp Configuration using Snmp GeneralAccess protection in Snmp Accessing tables and parameters using SnmpCommand Target/Source Function Appending rows to tables using Snmp Deleting rows in tables using SnmpIP address IP-netmask Router name Distance Management Information Base MIB Error messages via Snmp trapConfiguration modes Password protection Security for your configurationLogin barring Operating modes and functionsSecurity for your LAN Access control via TCP/IPGlobally to TCP/IP packet filters EncryptionHiding place-IP masquerading NAT, PAT IP routing table IP routingIP address IP netmask Router Dis Tance 192.168.130.0 255.255.255.0 IP address IP netmask Router name Dist This is what happensWhat information is propagated by IP/RIP? Dynamic routing with IP/RIPWhat do the entries mean? IP address IP netmask Time Distance RouterInteraction of static and dynamic tables Local routingTwo addresses for the router IP masquerading NAT, PATSimple and inverse masquerading How does IP masquerading work?Cable TV net WorkDNS forwarding Which protocols can be transmitted using IP masquerading?Only small difference is that Rator BridgingWhat are the filter options? Automatic address administration with DhcpDhcp server Dhcp clientCable modem really belongs to two LANs IP address Network mask Broadcast addressDhcp on, off or auto? Default state is autoHow are the addresses assigned? IP address assignmentNetwork mask assignment Default gateway assignmentBroadcast address assignment DNS server assignmentPriority for a workstation-overwriting an assignment Priority for the Dhcp server Request assignmentOperating modes and functions Operating modes and functions Elsa MicroLink Cable Two standards get around this problem AccessCable modem technology StandardsNetwork of the cable network Cable TV net Registration in the cable networkOperator Work Registration Network and its components Network technologyConnection modes Host Kinds of networks IP addressingSame IP address, this time with another netmask ExamplesThis address Bytes Looks like this in bits 10.0.0.0 255.0.0.0 IP address Netmask RemarkIP routing and hierarchical IP addressing There are two considerations when using these IP addressesHost Smith External host Marketing Example Expansion through local networks 80-C7-6D-A4-6E Why a LAN is called multiprotocol-capableEasy as possible That is processed by all computers in the LANInterface only understands MAC addresses Data transfer within the LANLAN as easy as possible Host Smith LAN coupling on MAC basis Data transfer from the LAN onto the InternetTechnical basics Elsa MicroLink Cable Appendix Technical dataService Package contentsWarranty coverage Warranty conditionsWarranty period Warranty procedureAdditional regulations Operating mistakesTypenbezeichnung Declaration of conformityAppendix Elsa MicroLink Cable Index 32, 40 Gateway Heap reserve Inde7017, 32 17, 18Trace SetupInde72 Wireless linksDescription of the menu options R73 SymbolsOverview of the menus R74 Description of the menu optionsDescription of the menu options R75 StatusStatus Running status displays Status/Current-time Status/Operating-timeStatus/Cable-statistics R76 Description of the menu optionsDescription of the menu options R77 Status/LAN-statisticsLAN-statistics Running status displays R78 Description of the menu options Status/Bridge-statisticsCannot be modified manually Bridge-statistics Running status displaysDescription of the menu options R79 Status/TCP-IP-statisticsStatus/TCP-IP-statistics/ARP-statistics These statistics include the following valuesStatus/TCP-IP-statistics/IP-statistics R80 Description of the menu optionsStatus/TCP-IP-statistics/ICMP-statistics Status/TCP-IP-statistics/TCP-statistics Description of the menu options R81Status/TCP-IP-statistics/TFTP-statistics Status/TCP-IP-statistics/DHCP-statistics R82 Description of the menu optionsDescription of the menu options R83 Status/IP-router-statisticsShrinks accordingly. It has the following layout IP-router-statistics Statistics from the IP router areaStatus/IP-router-statistics/RIP-statistics R84 Description of the menu optionsProtocol LAN-tx Cable-tx IP-address IP-netmask Time Distance RouterConfig-statistics Remote configuration statistics Status/Config-statisticsStatus/Queue-statistics Description of the menu options R85IPr-RIP-queue-packets R86 Description of the menu optionsStatus/Init-status Status/MCNS-statisticsDescription of the menu options R87 MCSN-statisticsSystem configuration SetupStatus/DHCP-client-statistics R88 Description of the menu optionsSetup/LAN-module Setup/Cable-moduleEntering the following command Default configuration, no name is enteredR90 Description of the menu options Setup/Bridge-moduleDescription of the menu options R91 Setup/TCP-IP-moduleMAC-address field R92 Description of the menu options Configuration, the TCP/IP module is activatedDescription of the menu options R93 Configuration, the IP router module is activated Setup/IP-router-moduleIP-address Node-ID Last-access Connect IP-router-module IP router module settingsIP-address IP netmask Router-name Distance Description of the menu options R95Routing-method Routing method settings Setup/IP-router-module/Routing-methodR96 Description of the menu options Different settings have the following meaning Setup/IP-router-module/RIP-configurationSettings have the following meaning Description of the menu options R97R98 Description of the menu options Setup/IP-router-module/MasqueradingFollowing layout Description of the menu options R99 Setup/IP-router-module/firewallR10 Description of the menu options Setup/DHCP-server-module Setup/SNMP-moduleDescription of the menu options R10 On The device operates as a Dhcp serverR102 Description of the menu options Default value of 6000 minutes equals approximately 4 daysOff The device does not operate as a Dhcp server Network mask is assigned in the same way as the IP addressIP-address Node-ID Timeout Hostname Type Setup/Config-moduleConfig-module Configuration module settings Description of the menu options R103Firmware Firmware Display and keyboard settingsR104 Description of the menu options Module Version Description of the menu options R105Position Status Version Date Size Index Other This option allows you to reboot the deviceR106 Description of the menu options Other menu allows you to manage the following functions