Adder Technology AdderView CATx EPS-S8 - Manual (Page 104)

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Ports
If.you.accept.the.analogy.of. IP addresses .being.rather.like.telephone.numbers,.
then.think.of.ports.as.extension.numbers..In.a.company.of.any.size,.you.
generally.wouldn’t.expect.the.accounts.department.to.share.the.same.telephone.
with.the.technical.department..Although.their.calls.may.all.be.related.to.the.
same.company,.they.concern.very.different.aspects.of.that.company..
It.is.the.same.with.IP.network.connections..Although.you.have.only.one.network.
link.into.your.computer.and.only.one.IP.address.(phone.number),.you.are.
probably.performing.many.different.tasks.through.that.one.link,.often.at.the.
same.time..Thus,.when.you.browse.the.web.your.outgoing.requests.and.the.
incoming.information.are.all.channelled.through.port.80..When.you.send.an.
email,.it.travels.through.port.25.and.when.you.transfer.files.you.are,.without.
knowing.it,.using.port.20.
At.the.“border.crossing”.between.the.wider.Internet.and.every.local.network.
attached.to.it,.there.is.a.router.that.is.usually.combined.with.a.firewall..One.of.
its.main.tasks.is.to.direct.incoming.traffic.to.the.correct.place.within.its.local.
network..A.key.piece.of.information.to.help.it.do.this.is.the.port.number:.
Security issues with ports
The.settings.of.port.numbers.become.important.when.the.AdderView.CATx.IP.
is.situated.behind.a.network.firewall..In.order.for.a.remote.VNC.viewer.or.web.
browser.to.make.contact.with.your.AdderView.CATx.IP,.it.is.necessary.for.the.
firewall.to.allow.communication.through.a.particular.numbered.port.to.occur..
One.specific.function.of.firewalls.is.to.restrict.access.to.ports.in.order.to.prevent.
malicious.attackers.using.them.as.a.route.into.your.network..Every.new.port.that.
is.opened.offers.a.new.possibility.for.hackers.and.so.the.number.of.accessible.
ports.is.purposefully.kept.to.a.minimum..In.such.cases,.it.may.be.advantageous.
to.change.one.or.both.AdderView.CATx.IP.ports.to.use.the.same.number..The.
other.alternative.is.to.place.the.AdderView.CATx.IP.unit.outside.the.firewall.and.
take.full.advantage.of.its.secure.operation.features.–.see.
Networking issues .for.
details.
IMPORTANT: The correct configuration of routers and firewalls requires
advanced networking skills and intimate knowledge of the particular network.
Adder Technology cannot provide specific advice on how to configure your
network devices and strongly recommend that such tasks are carried out by a
qualified professional.
AdderView.CATx.IP.has.
the.local.IP.address:.
192.168.0.3
User.with.VNC.viewer.accesses.
IP.address:.129.7.1.10.(this.
automatically.uses.port.5900)..
Router/firewall address: 9...0
Router.is.programmed.to.send.port.5900.
VNC.traffic.to.local.address.192.168.0.3.
and.port.80.web.traffic.to.local.address.
192.168.0.42
.
User.accesses.the.company.
website.at:.129.7.1.10.(this.
automatically.uses.port.80)..
Web.server.has.the.local.
IP.address:.192.168.0.42