I have a Yun 5 of them actually and I want to connect them to with Ethernet to control devices with a relay shield. I have gone into the Linux side of the yun and set the wan to eth 1 and uploaded the Blynk sketch to the yun. Next I have plugged in the yun to an Ethernet network and I cant get the Blynk to come on line. In my troubleshooting I connected the yun to a different Ethernet network and Blynk still wont come up. Finally I connected it to a third network and Blynk came online in about 4 minutes. Would this have something to do with the ip scheme on the networks as that is the only think I can think of that is different in the 3 networks. The one that it works on is the generic 192.168.1.x, one of the ones that it will not work on is 192.168.10.x and the other is (I think) 10.10.1.x. I can't see why that this would make any difference unless Blynk itself is looking at 192.168.1.x addressing somehow. Any help would be appreciated. I have projects that all have to use Ethernet and all my boards are doing the same thing. The 4th and 5th board fired right up and have had no issues. With the 5th board on one of the networks that the others wont work on. the other thing I noticed when I do an ip scan is that the original board shows up with a manufacturer of Gheo Sa, and the others all show up as Dog Hunter.
Ideally they all need to be on the same subnet eg. 192.168.10.xx if that is your local subnet.
It may be able to find other IP's but as you noticed it can take time for the routing or wont work at all.
Log into the Linux side and set the IP's as you need there are a few ways with the YUN including it net interface which is usually easiest.
There is also a quite major update for the YUN's mentioned in the YUN section which is where we will ask the mods to move this for you.
I am familiar with network structure. I brought the board home and plugged into my home network that uses 10.10.1.xx. When I plugged in the one from work it popped right up and worked like a champ for about 30 min. then when offline. So I uploaded the sketch into another one I have here and plugged it in and is seem to work about 30 min or so (not sure as I'm not continuously on my phone watching. but then it goes off line as well. When I reboot it will go online for awhile again. I was sifting through the Blynk info and one of the items said to make sure that I had a port open in my router. I am not sure how to just open a port. I know how to forward a port to an ip address but I have more than one Yun that I need to operate Blynk on. I'm getting pretty discouraged with Blynk. I have a couple of spark fun Blynk board that I don't use as they too seemed very intermittent with their connection that I blamed on their being very cheep. Now I'm thinking that it may be something else and have no idea where to start looking.
I used "BLYNK" for a little while myself but wasnt all that bothered about it as I kept going back to EASYIOT and have always been a fan of THINGSPEAK.