how to set static IP address which is gotten via DHCP

Hello Hae

Why would you want to have Static v/s Dynamic IP allocation in such a manner. Please explain?

Hi Amit, 

since my device need valid IP address assigned at first time to communicate with server.

If IP is assigned, device can use it as static one. don't need to change or reassign IP.

after that, I think device don't need DHCP at all. 

Best Regards,

Hae Ryong

Hello Hae

Normally when a DHCP server assigns an IP address, then it continues on the network as long as the client uses the IP address. So you do not need to make it static.

If the IP address gets de-allocated then the client can renegotiate under dynamic allocation.

Hello Amit, 

Yes, you are right.

my concern is when board is restarted, it try to get IP address via DHCP, it takes around 3 sec.

I think it is not necessary to wait 3 sec to make connection with server.

If I change it as static one, I think I can reduce 3 sec. in connection time .

Best Regards,

Hae Ryong

Hello Hae Ryonh,

But a Static IP address may not work on every network.

Hello Amit, 

Device already get IP address assigned by DHCP, so it is available for that network. then can use it as static one. I think.

Best Regards,

Hae Ryong

Hae Ryong Jung said:

Device already get IP address assigned by DHCP, so it is available for that network. then can use it as static one. I think.

Unless the DHCP server re-assigns the IP address to another device. How do you plan on preventing that?

Robert

Hello Robert

Or the server cache was cleared?

Hi All, 

Thanks for your concern.

My plan is that device is almost always exist in the network. device would not disconnect and reconnect frequently. never go to power off in working condition.

so IP is assigned at first connection, then it is OK for device to use IP as static one.

if IP address need to be reassigned for the device, I would like to delete IP address from the device and activate DHCP to provide IP like first connection to the network. (this network is private one)

Best Regards,

Hae Ryong

If the client does not renew the lease periodically then the IP address returns to the pool of available addresses to be reassigned.

Simply assigning a static IP address when you can would be both simpler and more robust than what you have described.

Robert

Hi Robert.

OK, DHCP seems not so good for this purpose.

I would not use DHCP for the device.

Thanks for your time and discussion.

Best Regards,

Hae Ryong

Hello Robert

Static IP would mean that the IP address is available on every network and the router/switch does not drop/discard packet on better-tightly managed network

No, it just means it's not in the DHCP available to lease pool. It's still subject to all the other rules. It does mean you have to reserve a pool of static addresses in the DHCP server but that's fairly common. Printers for instance are often assigned static IP addresses as are routers and of course DNS Servers.

That does assume you can get a static IP on your network of course. If not then you must fall back to DHCP. Static IP addresses are more work to manage but they can work.

Robert

It seems like forever but DHCP has only been around for about 20 years

Hello Robert

And that is a consideration that needs to be taken into account when the network management is setup.

Hi Amit,

I also have request from customer to preset a static IP (via USB connection to the device during configuration phase), so I plan the following

I will store the static IP in EEPROM

When booting, if it is 0 or 0xfffffff, I will use DHCP, otherwise I will use whatever static IP in EEPROM

Based on enet_lwip example, which was on DHCP, I changed lwIPInit to something like this:

lwIPInit (g_ui32SysClock, pui8MACArray, inet_addr ("192.168.0.22"), inet_addr("255.255.255.0"), 0, IPADDR_USE_STATIC);

The program runs, but it doesn't get the IP as I expected (switching back to DHCP, everything works fine)

Any pointer?

Thanks!

David