Subject: pinging problem

From: Vijayendra Sharma <[email-masked]>
Date: 9 Jun 2001 06:30:29 MDT

Hello sir,
   Can you help me with this problem,
 Will machines A and B able to ping eachother,

      A                                B
1)192.168.0.1/16-----Hub------192.168.0.2/24

2)192.168.0.1/16-----Switch------192.168.0.2/24

3)192.168.0.1/16-----Router------192.168.0.2/24

 i will be helpful to you, if you can help me in anyway.
regards,
    Vijayendra.

____________________________________________________________________
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---

From: CARDOSO Jorge Miguel <[email-masked]>
Date: Sat, 9 Jun 2001 17:26:37 +0100

|o|

rotfl

vIjaYenDra is this problem a little gamE? |o|

i think its the third email i receive with same question!! congratulations,
your persistence gives you the answers:

Comments to your choosen addressing scheeme: 
- network addressing 192.168.0.x/ 24 should not be used under normal
conditions and it would not be possible to configure it with some routers
because its a subnetzero. Has an example, for use it with Cisco routers, you
need to use the ios  command 'ip subnet-zero'.

case 1)
-------
A and B can ping eachother.

case 2)
-------
The answer is variable concerning the switch type and configuration.
Is it a multilayer switch?
Have you configured Vlans on this switch?

The answer is: A and B will ping eachother if they are on the same broadcast
domain (on the same lan segment/ on the same vlan).

case 3)
-------
A will not reach B unless the router is configured with bridging.
Look: under this scenario A thinks that will find layer 2 address
(MAC-address) of B and it will ask for it with an arpRequest but will never
get any ArpReply from B because they are on different broadcast domains.

Under a normal circunstance with choosen mask A 192.168.0.x/24, the process
would be like this:

- host A guess that 192.168.0.2 its not on the same broadcast domain using
the mask /24, so it would ask the layer 2 address of the gateway and not the
layer 2 address of B;
- host A would receive the MAC address of the router, and it would deliver
all the packets to the router;
- the router would look to layer 3 address of the packets, search the
outgoing interface and obtain the layer 2 address of B;
- the router would change destination layer 2 address of the packets to B
mac-address and then send it to the lan segment were B is located.

* NoW it's weekend time, forget for a while the insipid network concepts and
enjoy the sun with your girlfriend! have a nice weekend full of bits and
moon and sea and peace and love.

j0rge card0s0

-----Original Message-----
From: Vijayendra Sharma
To: [email-masked]
Sent: 09-06-2001 13:30
Subject: pinging problem

Hello sir,

      A                                B

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From: [email-masked]
Date: Mon, 11 Jun 2001 09:46:03 +0200

Dear Vijayendra,

I may be wrong, but I think you are looking for simpler answers than the ones I
have seen on the list. If this is a simple problem for IP beginners the
questions are:

A) Can machines with diferent subnet mask but on the same addressing space ping
eachother?

     YES. Cases 1 and 2 should ping eachother even with that "unproper"
addressing scheme.

B) Should routers route the private addressing spaces?

     NO. Case 3 should not ping eachother because routers do not route private
addresses. (On real implementacion, there are configuration parameter to
overrule this as Jorge explained.)

Vijayendra Sharma <[email-masked]> con fecha 09/06/2001 02:30:29 PM

Destinatarios: [email-masked]
CC:      (cci: Joaquin Rivera Rodriguez/TDC)
Asunto: pinging problem

Hello sir,

      A                                B

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From: CARDOSO Jorge Miguel <[email-masked]>
Date: Mon, 11 Jun 2001 11:20:27 +0100

No problem using private addressing scheeme on VPNs (Virtual Private
Networks)!
On this unreal case, the question is the choice of the subnetzero (the first
subnet should be avoided) and the mask.

-----Original Message-----
From: [email-masked]
[mailto:[email-masked]]
Sent: 11 June 2001 08:46 fr
To: Vijayendra Sharma
Cc: [email-masked]
Subject: Re: pinging problem

Dear Vijayendra,

I may be wrong, but I think you are looking for simpler answers than the
ones I
have seen on the list. If this is a simple problem for IP beginners the
questions are:

A) Can machines with diferent subnet mask but on the same addressing space
ping
eachother?

     NO. Case 3 should not ping eachother because routers do not route
private
addresses. (On real implementacion, there are configuration parameter to
overrule this as Jorge explained.)

Vijayendra Sharma <[email-masked]> con fecha 09/06/2001 02:30:29
PM

Hello sir,

      A                                B