Chief Delphi - Static IP vs DHCP

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Chief Delphi (http://www.chiefdelphi.com/forums/index.php)

- Programming (http://www.chiefdelphi.com/forums/forumdisplay.php?f=51)

- - Static IP vs DHCP (http://www.chiefdelphi.com/forums/showthread.php?t=153520)

andrewthomas

12-01-2017 16:07

Re: Static IP vs DHCP

Quote:

Originally Posted by billbo911 (Post 1630116)

This is one area that I have a strong opinion on.

If reliability is one of your team's goals for the season, then why take a risk on mDNS?
Yes, usually mDNS works just fine. But, I did say usually.

Why not just lock down your IPs to KNOWN values and move on.
They won't change, you know where each device is addressed, and connections on the field will JUST WORK! What more could you ask for?
Well, OK, you could ask for an easy to find guide to setting your IP's statically. Fortunately, this thread already has what you really need to know.

Couldn't agree with this more. At the end of the day, mDNS (DHCP) doesn't buy you much.

As for the IPs themselves, I wouldn't be too worried. Last year, our roboRIO and Driver Station IPs were correct, but we got away with our other device (Jetson) as 10.TE.AM.25. Where we did get hung up, however, was with FMS allowed network ports. Make sure to double check your SSH, camera stream, etc. port configurations (http://wpilib.screenstepslive.com/s/...ms-whitepaper).

rich2202

12-01-2017 19:10

Re: Static IP vs DHCP

Quote:

Originally Posted by scca229 (Post 1630109)

Going to just highlight this one from marshall's post.

Driver Station - Static 10.TE.AM.5 would be a reasonable choice, subnet mask must be 255.0.0.0

When there is a communication problem on a DS and they have informed me they are using static IPs, or I drag it out of them after getting the deer-in-the-headlights look when I ask, this is very often the issue. Everyone is so used to using /24 submasks (255.255.255.0) when this particular one must be a /8 (255.0.0.0). The funny thing is that most versions of Windows that I know of automatically default to a /8 when you enter a 10. IP.

255.255.255.0 was useful when imaging the crio. The program would search all possible internet address. Using the small address space (subnet mask) speeded things up. However, once we go to a competition, we had to change it to 255.0.0.0. Otherwise it couldn't talk to FMS. Too bad they couldn't write FMS with a simulated IP address of 10.xx.yy.255 for each team.

sraque

13-01-2017 07:13

Re: Static IP vs DHCP

If you set static IPs, make sure many kids on the team know it and can tell anyone who comes to help them with their robot. I have spent many hours trying to help teams with Comms issues only to find out that the one network-savvy person on the team decided to set static IPs and then didn't come to the competition, and no one present knew about it.

rich2202

13-01-2017 10:33

Re: Static IP vs DHCP

Quote:

Originally Posted by sraque (Post 1630405)

We put a sticker with the Static IP Address on all the devices.

It started because we have multiple driver station/programming computers, as well as multiple cameras.

If CSA help is needed, it is immediately obvious that we are using Static IP's, and the address of that device.

jlindquist74

13-01-2017 15:22

Re: Static IP vs DHCP

Quote:

Originally Posted by andrewthomas (Post 1630134)

Couldn't agree with this more. At the end of the day, mDNS (DHCP) doesn't buy you much.

Please don't use those terms as if they mean the same thing. They really, truly, vastly DO NOT.

Greatly simplified:

DHCP is how a host, lacking its own address, asks a server to assign it one. (It requires a DHCP server to be present somewhere on the local network in order to work.)
mDNS is how a host, lacking the address of another host on the local network, asks that other host to provide its address. (It does NOT require a server to work.)

How those protocols are implemented and used varies with the operating system. Of course, Windows has peculiar issues about mDNS, which complicates things. It certainly keeps our work from being boring!

Conor Ryan

13-01-2017 15:30

Re: Static IP vs DHCP

always static IPs. Its like using mail with a full mailing address then Zip Code + 4, using DHCP is like "Please mr. postman please deliver me to mr. rio. I promise i paid postage." It is in your own network so just make it specific.

andrewthomas

13-01-2017 15:51

Re: Static IP vs DHCP

Quote:

Originally Posted by jlindquist74 (Post 1630676)

Please don't use those terms as if they mean the same thing. They really, truly, vastly DO NOT.

Greatly simplified:

DHCP is how a host, lacking its own address, asks a server to assign it one. (It requires a DHCP server to be present somewhere on the local network in order to work.)
mDNS is how a host, lacking the address of another host on the local network, asks that other host to provide its address. (It does NOT require a server to work.)

Yes, this is true. I was merely relating this option back to OPs original "Static IP vs DHCP".

AustinSchuh

14-01-2017 03:40

Re: Static IP vs DHCP

Quote:

Originally Posted by jlindquist74 (Post 1630676)

DHCP is how a host, lacking its own address, asks a server to assign it one. (It requires a DHCP server to be present somewhere on the local network in order to work.)
mDNS is how a host, lacking the address of another host on the local network, asks that other host to provide its address. (It does NOT require a server to work.)

The fun one is what happens when you plug your DS into the robot (a network without a DHCP server). Turns out, you get a link local IPv6 address which can be found via mDNS, allowing the two devices to communicate. Sometimes, if you are luck and everything works. We just gave up debugging the various issues we ran into and put everything on static IP addresses.

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