Re: Problem related with Subnetting
From: Wolf (wolfdotcom_at_hotmail.com)
Date: 12/05/04
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Date: Sun, 05 Dec 2004 18:49:36 GMT
First, although these IP nets are just an example I would
encourage you to only use private addresses as defined in
RFC1918 unless they have been issued to you.
Whew, a lot of really good questions.
> Hi all,
> I have a problem to discuess, related with Subnetting issues.>
>
> As in corporate intranets, if a third party based conference(group
> chat) is going on, having server outside of that company scope. Now
> say if that company has broke down its intranet in to 3 different LANs
> with help of routers, with subnet address of 10.0.0.X, 20.0.0.X,
> 30.0.0.X. Say the address provided by the ISP to that company is
a> .b.c.d, i.e. WAN address for main DSL router.
> Now all the conversation going on is having intervention of third
> party server. So if there is one client involved in each of subnet,
> then the server will be having 3 separate connection for each client
> for transmission.
I am guessing you mean a router-and the answer is yes you
need a router to route across subnets. Yes you will need to
perform three transactions.
>
> So every time if any client send something to group, that same data
> will come to all 3 streams, intended to same IP address i.e. a.b.c.d.
> So it means a overhead, though we are sending same data to a corporate
> intranet, but having 3 separate streams. Which should be like that,
> server will send only one stream to a.b.c.d, later this stream will be
> divided into 3 stream, but inside the intranet, and each one will go
> to the respective client. OR One way can be like that, the outside
> server will send to one client only and this will multicast this data
> to others(rest of 2).
The same data will have to be routed to all three client which are in
three different subnets-yes. Multicast is only really relevant inside
your subnet.
> Can any body comment on this problem.
>
> One more thing, I am quite confuse with subnet addressing. Like if one
> host from 20.0.0.X LAN want to send a packet to a host in 10.0.0.X LAN.
> So what destination address it will choose, and at the receiver end what
> source address we will get. Assuming router's of those subnet having
> their WAN address as 192.0.1.3 and 192.0.1.2 respectively. Will it be the
> same source and destination address??
The packet (layer 3) will be addressed to 20.0.0.X from 10.0.0.X. At layer
2 it will get encapsulated with your real MAC address and the MAC address
of the router. The router will NAT your address and change the router MAC
address either to the host at 20.0.0.X if it has a direct connection or the
next
hop router if not and send it out the door. If it does not know where to
send it,
it will drop the packet.
> And how the routers, which are making a subnet, make this intellegent
> translation, like how to map 192.0.1.2 address to exact host of
> 10.0.0.X.
Routers will map using NAT and/or PAT. Consumer DSL routers use PAT
NAT: If you have a /32 (192.0.1.0/32) your ISP knows to route anything
to that network to your router (192.0.1.1). Your router has a table which
say that any packet going into 192.0.1.1 needs to be translated to
10.0.0.10,
and any packets leaving needs to be translated to 192.0.1.1 The Internet
then knows your server as 192.0.1.1
PAT: Using the same example, If you use your last IP address 192.0.1.6 as
your overload address, the router's address translation table gets a little
more complex. Besides having your PC's address (10.0.10.8 for example),
it will also include the port number you are using to talk to the router,
and the
address and port number of the target host it is talking to. That is how it
knows
where to send packets that come in.
> Though I know, that I couldn't explain my problem in right manner, but
> still waiting for some +ve response.
Well, here's my shot. HTH
> Regards,
> Rajat.
Regards,
-- Wolf ---------------------------------------------------------------- Please post all responses to UseNet. All email cheerfully and automagically routed to Dave Null
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