Debugging Outlook :)

My colleague Mr.X sitting next to me was configuring mail in his new laptop..

Mr.X - Anoop, tell me the outlook configurations..

Anoop - Give this IP to SMTP, POP etc.. Give username/pwd etc etc

Mr.X did configurations and some more debugging.. still he is not able to download mails.

I looked into my own configurations again.., and started googling also... could not find anything..

I peeped into his desk... it was a shocking scene.. cables are not connected yet :)

Being in a networking ODC, we even forget to plug in the network cables..!

Layer n device

When does we call something a layer 3 or layer 2 device ?

A router is a layer 3 device because it takes forwarding and routing decisions depending on the Layer 3 header. Also Layer 2 header addresses gets changed when it passes through a router.

So whether we can call a Switch - who can create VLANs based on IP addresses a Layer 3 device ? May be or may not. Although it looks into the IP headers, the Layer 2 addresses remain unchanged even after it goes through a VLAN switch. So its still a Layer 2 device.

Disclaimer: I am just understanding networking and discussing myself. My interpretations may be wrong.

Feedbacks I received on this from a networking expert:
A device is in l2, if it does l2 fn, i.e., bridging
device is l3, if it routes
if a switch routes packets, it is a router

TCP/IP socket - in a multi-homed host

In a multi-homed host ( host having two more network addresses), how does a TCP/IP socket connection behave ?

How does it find the interface through which packet has to be forwarded ? It depends on the entries in the forward information table.. ( or route table - ).. if there are more than one interface to the same destination it looks for the lowest Metric value.. or if it does not find an entry it forwards through the default route gateway interface..

Then how does it determines through which interface it should listen for the reply ? If "bind" is not explicitly called, the TCP/IP socket will listen on the interface through which the packet was forwarded..!

Using "bind" before "connect", we can explicitly bind a interface, if needed..