tempts using the pa ra me ter »Time bet ween at tempts« in the con fi gu ra ti on item Net work In ter net. You can set the
num ber of at tempts and the in ter val bet ween the se at tempts se pa ra te ly for each ISP that has been con fi gu red.
Af ter that, the PABX sys tem will use the next ISP con fi gu red in the list for at temp ting to set up a con nec ti on.
If the con nec ti on is dis rup ted and an at tempt is to be made la ter to re-estab lish the con nec ti on, this cy cle is res tar ted
be gin ning with the first en try in the list.
Firewall
When you use NAT, the PCs con nec ted to the PABX are well pro tec ted against at tacks from the In ter net.
If you wish to have ad di tio nal se cu ri ty you can also use the in te gra ted pa cka ge Fil ter Fi re wall. A fi re wall acts as a lo gi -
cal wall for data pa ckets bet ween the In ter net and the LAN which has »ho les« for cer tain pa ckets (fi re wall ru les, also
known as fil ters), al lo wing the se pa ckets to pass through the wall. In the in iti al sta tus the fi re wall is con fi gu red such
that all data can pass through that are sent in the di rec ti on of the In ter net.
Note
An ex cep ti on to this rule is the »Net bi os fil ter: This fil ter pre vents the for war ding of Net bi os name que ries from
Wind ows PCs to the In ter net. As the na mes of the Wind ows PCs wit hin the LAN are not known in the In ter net, it is
not mea ning ful to estab lish an In ter net con nec ti on for for war ding the name que ry (this could re sult in con si der able
costs, as the se name que ries oc cur fre quent ly, mea ning that the In ter net con nec ti on would prac ti cal ly ne ver be ter -
mi na ted).
The fil ters are des cri bed by ru les who se con fi gu ra ti on re qui res ex pert knowled ge about the TCP/IP pro to col fa mi ly.
The fi re wall of your PABX sys tem can be ea si ly con fi gu red using a Fil ter Wi zard in which you need to in di ca te (in
plain text) whet her you wish to al low de fi ned ap pli ca tions ac cess to the In ter net.
To start the Fil ter Wi zard in the con fi gu ra ti on item »Net work fil ters« click the but ton »Fil ter Wi zard«. The fol lo wing
mask is then dis play ed af ter a war ning that star ting the Fil ter Wi zard will de le te all fil ters that have been con fi gu red
up to this time:
The Fil ter Wi zard can be res tar ted at any time to load a mo di fied (edi ted) con fi gu ra ti on into the PABX sys tem. Click
the but ton »Send con fi gu ra ti on data« to trans fer and ac ti va te the fil ters. Af ter the data is sent the new con fi gu ra ti on is
ac ti vat ed in the PABX sys tem and any on going In ter net con nec ti on is ter mi na ted.
The con nec ti on is re-estab lis hed ho we ver as soon as a data pa cket must be rou ted to the In ter net which the fi re wall
lets pass in ac cor dan ce with its con fi gu ra ti on.
Des crip ti on of the rou ter functions
63
Summary of Contents for elmeg T484
Page 1: ...Operating instructions English elmegT484 ...
Page 6: ...Table of contents ...
Page 78: ...Brief description of functions 72 ...
Page 85: ...79 ...