TTIG - Network / ARP issues and work around

Gateways TTIG - The Things Indoor Gateway
1

I set up a TTIG Indoor Gateway about 3 weeks ago. Since then, I noticed it was losing connection and reconnecting a few times an hour. The green LED would start flashing, and eventually go solid. I had a device sending an uplink packet every minute, so idle connections were not the problem.

After looking at some tcpdump captures, it appeared that my router / firewall (pfsense) was expiring its ARP cache entry for the TTIG every 20 minutes, which is definitely normal. However, the TTIG device was not responding to ARP requests from the router and eventually rebooting. This corresponded to the outages I was seeing. Last night, I added a static DHCP entry with a corresponding static ARP mapping, and this problem has not recurred.

This ARP response problem seems like a bug in the TTIG firmware. Coincidentally, I noticed it does not respond to pings unless pings are coming from the router. Does updated firmware fix this?

Anyway I hope this is helpful to anyone experiencing these sorts of problems. The static ARP entry definitely seems to work.

Dave

2

Hi Dave, these are interesting observations. However, I cannot reproduce neither of them.
My TTIG responds to ARP requests from my router (mikrotik):

494 19:48:28.961450 Routerbo_ff:ba:65   Broadcast           ARP  89 Who has 192.168.88.134? Tell 192.168.88.1
495 19:48:29.202363 Espressi_17:58:0f   Routerbo_ff:ba:65   ARP 107 192.168.88.134 is at dc:4f:22:17:58:0f

and to ICMP ping requests from other hosts:

    1 0.000000000 192.168.88.131 → 192.168.88.134 ICMP 98 Echo (ping) request  id=0x0002, seq=26/6656, ttl=64
    2 0.002894218 192.168.88.134 → 192.168.88.131 ICMP 98 Echo (ping) reply    id=0x0002, seq=26/6656, ttl=255 (request in 1)

There must be something peculiar about your network configuration. I would be interested to learn what exactly is causing this behavior in your setup.

3

I’ll see if I can narrow this down later in the week. It is odd that this is the only device on my network acting like this though. I will let you know what I find…

4

My TTIG does eventually respond to ARP requests. By “eventually”, it seems to be minutes later. I ran a “ping -i 10” for a while, got no responses. At the same time, I was running a tcpdump on my wifi to dump out any ARP packets. I saw requests, but no replies. A couple minutes later, several ARP replies were received. It was almost like they were queued up.

I am not sure what it is about my network. I do have a fair number of device on my home network (over 50) and there is a decent amount of broadcast traffic.

I did find this github issue that mentions ARP problems with esp8266 firmware: https://github.com/esp8266/Arduino/issues/6886 I am not sure if it’s relevant to this particular device, but it is curious.

5

Can you try the TTIG on another network - either via a smart phone tether or just take it somewhere else where you have access to WiFi.

That way, you get to find out if there is something curious about your own TTIG or if it’s just generic (which is the more likely).