Operation Manual

Operating modes and functions

ELSA LANCOM Wireless

English

The router can check the source and destination ports of data packets using the TCP or

UDP protocols. It can then deduce the purpose of the data from these ports. For example,

FTP accesses or Telnet sessions can be identified.

Proxy-ARP

A special feature of the IP router is the proxy ARP. This proxy is used if the transmission

of data to IP addresses takes place in the same logical network as the sender, but the

destination address is still reached via a router. This is the case when individual

workstation computers (teleworkers) are networked via TCP/IP to the company network.

The teleworker then has an IP address which is located in the same local network as all

the other computers in the LAN. A data packet from LAN to the teleworker would usually

only search for a receiver locally, but would not be able to find one.

To take advantage of this function, enable the 'Proxy ARP active' option (in LANconfig in

the 'TCP/IP' configuration section on the 'Routing' tab or in the

/Setup/IP-router-

module

menu for other configuration modes).

The router becomes a proxy for the teleworker with the following entry in the routing

table:

Proxy hosts are not propagated in an RIP packet because the router responds to an ARP

request for the proxy computer with its own MAC address. The distance is set to '0' on

the routing table to indicate this clearly.

The router now responds to the request for the MAC address to the IP address

192.168.110.123 with its own MAC address. This ensures that all packets in the LAN for

the teleworker are now automatically sent to the router, and that data is sent on to the

computer at the other end of the ISDN connection.

Local routing

You know the following behavior of a workstation within a local network: The computer

searches for a router to assist with transmitting a data packet to an IP address which is

not on its own LAN. This router is usually notified to the operating system by its property

of being the default router or gateway. It is often only possible to enter one default router

which is supposed to be able to reach all the IP addresses which are unknown to the

workstation computer if there are several routers in a network. Occasionally, however,

this default router cannot reach the destination network itself but does know another

router which can find this destination.

IP address Netmask Router Distance Masquerade

192.168.110.123 255.255.255.255 Teleworker01 0 off