Hello,

 

Sorry everyone, this is going to be a little long.

 

First off, let me say that I have very little knowledge 

about networking.  That said, I'm attempting to use 

the Microchip stack to send UDP packets to the 

internet.  My hardware configuration is an ENC28J60 

and several PCs connected to a LYNKSYS router/hub, 

the WAN side of the router connected to a cable modem.

 

It appears to me from reading the documentation for 

the stack (AN833) that to send a UDP packet to the 

Internet, I need local and remote port numbers, IP address 

AND a MAC address.  I know the ports and IP address; 

however, the MAC address is unknown.

 

>From reading a few documents on the internet as 

primers (RFC 1180 included), I don't really know what 

to use for the MAC address.  My experiments so far 

have shown that if I use the MAC address from the 

LAN side of the LYNKSYS router (IP 192.168.1.1), I can 

access the internet server.  I can also use ARP with just 

the internet server's IP address to return a MAC (not the 

same as my LYNKSYS MAC), which also allows 

access to the server.  So, several questions:

 

1. Is the MAC address returned with ARP the actual 
    server, or is it a computer between the router and the server?

2. Which MAC should I use, and why?

3. How often should I use ARP to get a new address?  I 
imagine that unless the internet breaks, the server computer 
is replaced or similar, that the MAC will remain the same.  
Should I just ARP once and store it in eeprom, or when 
the server stops talking for a period of time, or at every 
power cycle, or once/day...?  What is "standard"?

4. Does using the MAC not associated with the router 
"bypass" or in anyway open me up to virus/hacking issues?

5.Is it "normal" to have to ARP for a MAC to send a UDP 
packet ( it appears to be required in the microchip stack)?
In my limited past network forays, I used a class 
library that encapsulated all this, I just needed to send in 
the port numbers and the domain name (yes, I still need 
to figure out how to access a DNS server for IP resolution).
 

Thanks for any help.

 

Ken

klumia@adelphia.net

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