Couple of networking questions...

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digitaloracle

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1.)How do computers handle multiple network adapters?
2.)How do they handle both dial-up (or other temporary connections) and an ethernet?
3.)What happens if they both have interent connectivity?
4.)How does NAT work OR How does a router determine what needs to be sent over it's WAN connection? How does it know who to rely the replies back to?

Links would be fine, but I'll probably be back with more questions after reading up :)

Thanks, these have been bothering me for some time.
 
digitaloracle said:
1.)How do computers handle multiple network adapters?
2.)How do they handle both dial-up (or other temporary connections) and an ethernet?
3.)What happens if they both have interent connectivity?
4.)How does NAT work OR How does a router determine what needs to be sent over it's WAN connection? How does it know who to rely the replies back to?

Links would be fine, but I'll probably be back with more questions after reading up :)

Thanks, these have been bothering me for some time.

1) Each network adapter will create a new virtual connection in the Network Connections.
2/3) If you have dialup and the ethernet on, and they both have internet access at the same time, it depends on the program you are using to decide which one to use. For instance, in Internet Explorer properties, you can specify what connection to use by defailt. If you have to ethernet connections plugged in that have internet access, you could run into trouble unless you specify exactly which NIC to use.
4) On the LAN, if your computer sends a request, it hits the router. The router then looks in its tables and sees if it knows how to get to where you are looking for, or if it needs to use another means of resolving the name, this is DNS. When your router sends out the packet asking the DNS server how to find a certain location, it adds it to its own table. When the DNS server responds back to the router, the router will know that your computer on the LAN requested that resource from the WAN based on its routing table.

This is about as simple as I can put it, routers are a bit complicated, but the example I gave it just with DNS.
 
Thanks for the answers.

I thought your computer resolved the DNS names when it needed to, not your router. My router happens to be able to serve as a "virtual" DNS server (I can tell windows it is my DNS and I guess it forwards requests on to TDS's (my ISP) servers.

A few more questions:
1.) In response to question 1: What about say, windows file sharing? Will it look for hosts on both adapters or just on one (assuming you have two ethernet adapters that can acsess seperate microsoft netoworks) and if so, how is that one determined?
2.)What if both adapter acsess the same network? Is one used as a default?
 
digitaloracle said:
Thanks for the answers.

I thought your computer resolved the DNS names when it needed to, not your router. My router happens to be able to serve as a "virtual" DNS server (I can tell windows it is my DNS and I guess it forwards requests on to TDS's (my ISP) servers.

Your computer does have dns tables of its own. However, when it can't find a matching entry, it'll send the request out to the gateway of unknown (cisco) or default gateway (win). This will happen until the path stops; meaning you reached an endpoint for dns...prolly inside the isp network.


A few more questions:
1.) In response to question 1: What about say, windows file sharing? Will it look for hosts on both adapters or just on one (assuming you have two ethernet adapters that can acsess seperate microsoft netoworks) and if so, how is that one determined?

2.)What if both adapter access the same network? Is one used as a default?

I've assumed that windows would have a default net adapter. This adapter would be labeled Net0 in the registry. I don't think windows is smart enough to failover to another connected adapter. It would be a fun setup to try out. I can't remember ever doing that in class.
 
OK. A few more:
1.)In brain's reply to #4, it was said that "when the request hits the router.." How does it get to the router? does it run through all of the network devices (such as switches) and none of them know what to do with it, causing them to "pass" the request along untill it gets to the router which decides to take care of it?

2.)Are these tables that are created by network devices shared(IE once on e device gets an entry it shares it with all other devices)?

3.)For basic switches (layer 2 I think is the correct term), they don't understand any of the higher protocols like TCP/IP and NetBIOS, so how do they get packets to where they need to go? Do the computers maintain tables of their own mapping IP adresses to MACs? How does a computer find an IP it has never looked for before?

I apologize for the continous streamof questions, but I really do want to understand this and have no acsess to any formal training. If anyone has links to "free" info/FAQ/tutorial/instruction sites, I would be most greatful.
 
1) the packets are sent to the next hop address/router. it goes router to router until it reaches an endpoint where if that router doesn't know where to forward it, it'll throw the packet in the bit bucket.

2) it's all about configuration. Admins can setup their devices to share information.

3) switches maintain a table of mac to switch ports. every port on a switch has a dedicated path to any other switch port on the same switch; switches provide dedicated bandwidth.

the process of resolving ip to mac or mac to ip is called ARP or RARP

from http://www.webopedia.com/TERM/A/ARP.html

Short for Address Resolution Protocol, a network layer protocol used to convert an IP address into a physical address (called a DLC address), such as an Ethernet address. A host wishing to obtain a physical address broadcasts an ARP request onto the TCP/IP network. The host on the network that has the IP address in the request then replies with its physical hardware address.
There is also Reverse ARP (RARP) which can be used by a host to discover its IP address. In this case, the host broadcasts its physical address and a RARP server replies with the host's IP address.
 
3.) And so once it has the physical address, the computer puts that in a table and uses it for future connections? Or does it redo the broadcast? Is this one of the problems Layer 3 switches alleviate (ie they map both physcial and TCP/IP)? What about on an internet-wide scale? I don't think that a single computer can send out a blanket broadcast for an ip across the whole net and expect anything to return in a timely fasion. And I assume other protocols use the same system (such as NetBIOS)

And a few more miscellaneous questions:
1.)How do you change TCP/IP settings via bash in linux?
2.)In the windows TCP/IP configuration settings, what exactly is the gateway? As soemone told me, the gateway connects two unlike networks, but what is this gateway? Is windows limited enough to make it an internet gateway without labling it as such? If so, what is the significance, as we established earlier that a computer doesn't nessecarily know when it needs to go through a router to acsess anything.
3.)Anyone that has replied, where did you learn it? Just time or experience, or was there someplace that taught it all?
 
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