IP aliasing

IP aliasing
I have a question about IP aliasing.

let us assume the OS is linux, if required.
I have one NIC which has one MAC address.
I create 2 IP addresses, both on the the single NIC, using IP aliasing.

Questions

1 What is the disadvantage in this method compared to having 2 seperate NICs?
2 I have read that the first IP Address is the real primary address (like a parent), and the second IP address is like a child riding piggyback on the first address. So what are the differences between the two ip addresses? Are there any disadvantages in using the second ip address?
3 Can I make network connections with other computers using both ip addresses (one per connection) and who (which protocol or layer) controls which ip address is used for which connection?
4 Can I decide which ip address is used for which connection?
5 Can I make a network connection between both these ip addresses, on the same computer, and use the connection to transfer files or chat, on the same computer?
6 Can I make the computer do IP aliasing with multilpe IP addreses from a DHCP Server?
7 Can both the addresses be used in VPN and IPSec
8 If the computer is behind a NAT Router, will the answers to any of the above questions be different? If so, please explain the differences (except the question about VPN and IPSec).

thanks in advance

 

To try to answer to some of the questions, mostly 3 and 4.

I use 2Nics connected to Different ISP,s. My router/gateway is UNIX/Freebsd. I use my Firewall (PacketFilter shortF) to direct the traffic from my lan computers to according ISP based on ports. This should work with 1 nic too.

http://www.openbsd.org/faq/pf/pools.html

I implemented a section Load Balancing for my needs.

Anyhow because youre not talking about your gateway, but a single machine connected, you should be able to bind your IP in question to software itself. Which one to use.

Also you can define some IP address/range with static routes

http://www.freebsd.org/doc/handbook/network-routing.html
section Setting Static Routes

But this is based on the destination IP or range used, not the port,protocol.

You also should be able to make connection between the 2 addresses. Doing DHCP for the second IP for the same NIC, i tried to find that some time ago but i can understand now that might not be possible. Possible because the MAC address and ISP settings

Anyway there´s alot of stuff to learn and read there, hope this gives some enlightment but it´s not something you could just do in a sec or have ready answer for.