TCP/IP stack and DNS problem

Daniele · Guest

Hello
I used the Microchip TCP stack converted by CCS on my own hardware and everything works ok.
I can use it as web server without any problem.
However In my application I need to use DNS feature.
It seems that there's no dedicated function to resolve hostname into IP address so I tryed to convert the DNS example supplied by CCS in order to use the Microchip stack.
But it doesn't work. In detail I have a timeout problem from the remote server.
I know there're several thing involved that can go wrong. At high level even my LAN gateway address (if I use the same I defined on Windows it doesn't even reply its MAC address, so i use the server DNS IP as gateway...)

In breaf, is there any already tested code that I can use, at least to avoid lower level problem ?

Thanks.
Daniele

Daniele · Guest

I partially solved the problem.
I used the DNS library supplied by Microchip and I can resolve hostname into their IP address.
However I still have the problem to obtain MAC address of my gateway.
It's a Cisco router/firewall. Is there something I had to know about accessing these kind of devices ?

Thanks.

PCM programmer · Joined: 06 Sep 2003 Posts: 21708

If it's attached to a Windows machine, just type: ipconfig /all

http://support.microsoft.com/kb/314850

asmallri · Joined: 12 Aug 2004 Posts: 1634 Location: Perth, Australia

Douglas Kennedy · Joined: 07 Sep 2003 Posts: 755 Location: Florida

Well to receive an IP address via DCHP you'll have to create a DHCP discover message (it uses UDP packets.) You then collect the offers ( in a simple system chances are there is only one) send a request to a chosen DHCP then you'll bind to an IP and a gateway IP for the permitted lease time.
The offers from the DCHP's will have their MAC addresses as wrappers to the UDP packets
Of course you can always just use a fixed IP and a known gateway IP

Guest · Posted: Tue Dec 05, 2006 12:42 am

Thanks for the reply.
Actually I already use fixed IP for PIC, DNS server and gateway.

The problem is obtaining from the gateway (a Cisco router) its MAC address in order to connect to internet (from PIC to Internet).

No problem if I ask the MAC of other Intranet machines but the gateway seems protected against this kind of request.
I know that the ARP proxy that can be disabled (but i don't beleive so), I'm waiting for the technician and see the set-up.

I still have to try to manually insert the gateway MAC address into the code and see what happen.

Thanks

asmallri · Joined: 12 Aug 2004 Posts: 1634 Location: Perth, Australia

Daniele · Guest

Thanks Andrew.

Actually I'm a bit confused. I tried inserting manually the router MAC address and it works. I just follow the Microchip DNS sample and i had back the page.

It could be possible to have some wrong setup but still working ?

Thanks,
Daniele

asmallri · Joined: 12 Aug 2004 Posts: 1634 Location: Perth, Australia

The MCHP stack is pretty crude. If you call ARP Resolve manually with the GW IP address it will populate the ARP cache for you.
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Daniele · Guest

Found the mistake.

The bit 0 of the first byte of MAC address specifies also if the sending frame is UNICAST or MULTICAST.
It seems that my (or every ?) router/gateway doesn't accept MULTICAST frame on ARP request.

I just change the default MAC address 01-02-03-04-05-06 into 00-02.... and everything works.

Sorry for my explanation, I have still to understand what this really means.

Thanks.