Garage drops off the network every few days?
December 1, 2024 6:19 AM Subscribe
What would cause my garage (which is connected to the rest of the house ethernet network via an ethernet cable) to drop off the network every x days (I will be trying to figure out exactly how long it goes, but I don't think it's regular)
The network topology is
Fibre modem -> Router - > Switch - > Switch - > Garage devices
When this happens, to get the devices to come back online again and have IP addresses, I need to power cycle the first switch (the one between the router and the second switch).
I would be surprised if it was something DHCP lease related?? But maybe? There are other device inside the house connected to the first switch and all of the other devices connected to the first switch are still online even while the garage is not. Power cycling the second switch doesn't help.
Fibre modem -> Router - > Switch - > Switch - > Garage devices
When this happens, to get the devices to come back online again and have IP addresses, I need to power cycle the first switch (the one between the router and the second switch).
I would be surprised if it was something DHCP lease related?? But maybe? There are other device inside the house connected to the first switch and all of the other devices connected to the first switch are still online even while the garage is not. Power cycling the second switch doesn't help.
What happens if you swap the garage switch for the house switch? Do the switches get assigned an IP address and do they have a configuration page (meaning they may not be just switches)?
Do either of these switches have a 'uplink' port, and are you using it to connect the switches together?
I would also try switching ports around like kbanas suggests.
posted by AzraelBrown at 6:58 AM on December 1 [2 favorites]
Do either of these switches have a 'uplink' port, and are you using it to connect the switches together?
I would also try switching ports around like kbanas suggests.
posted by AzraelBrown at 6:58 AM on December 1 [2 favorites]
When the garage is offline, look at the connection LEDs on both switches to find out if there's a cabling problem. If the switches have a configuration page (in which case they're smart switches or even fully managed switches), what do they report? You would need to access the garage switch from one of the devices there, or using a laptop that's configured to (at least temporarily) have an IP address in the same IP range as the garage switch.
posted by Stoneshop at 8:06 AM on December 1
posted by Stoneshop at 8:06 AM on December 1
How smart are the switches? Could one (or both) of them be configured to be doing DHCP rather than passing on the address request to the router?
Worst case is that the switch is answering the DHCP request *and* forwarding the broadcast to the router, so it’s a race for who answers first.
posted by Tell Me No Lies at 8:19 AM on December 1
Worst case is that the switch is answering the DHCP request *and* forwarding the broadcast to the router, so it’s a race for who answers first.
posted by Tell Me No Lies at 8:19 AM on December 1
also try swapping ports, etc. but:
what is the topology of your space? in other words, is your garage connected or detached? if it's detached, how long is the cable run to get to it and how is the cable strung (trenched, in exposed conduit, open air)? does the garage have a separate breaker panel from the main house? you can get Weird Stuff happening on sufficiently long runs and with devices that pull electricity from separate panels. this may also apply if your garage is attached but also has its own breaker panel too. (something something ground potential mismatch - someone with more knowledge of residential electrical can chime in with details..)
for what it's worth, if the cable run is sufficiently long the switch may not really be able to deal with the power requirement to throw the signal down the line, even if it's in the same building, especially if it's one that does "green ethernet" or "green power" or something along those lines. a desktop-style cheap switch may just not have the oomph if you're running 50+' of cable. (or, for that matter, the power brick could be just marginal enough that it's causing an issue. you could try replacing it - MeanWell power adapters are a good brand that's pretty readily available and can likely be found in the voltage that you need.)
posted by mrg at 8:49 AM on December 1
what is the topology of your space? in other words, is your garage connected or detached? if it's detached, how long is the cable run to get to it and how is the cable strung (trenched, in exposed conduit, open air)? does the garage have a separate breaker panel from the main house? you can get Weird Stuff happening on sufficiently long runs and with devices that pull electricity from separate panels. this may also apply if your garage is attached but also has its own breaker panel too. (something something ground potential mismatch - someone with more knowledge of residential electrical can chime in with details..)
for what it's worth, if the cable run is sufficiently long the switch may not really be able to deal with the power requirement to throw the signal down the line, even if it's in the same building, especially if it's one that does "green ethernet" or "green power" or something along those lines. a desktop-style cheap switch may just not have the oomph if you're running 50+' of cable. (or, for that matter, the power brick could be just marginal enough that it's causing an issue. you could try replacing it - MeanWell power adapters are a good brand that's pretty readily available and can likely be found in the voltage that you need.)
posted by mrg at 8:49 AM on December 1
You probably didn't make this dumb mistake like I did, but I had similar symptoms (connection dropping every few days) when I was double NAT-ing.
If you already know about the double NAT risk, then you probably don't need to worry.
(I did, but screwed up my settings anyway)
posted by Acari at 9:22 AM on December 1
If you already know about the double NAT risk, then you probably don't need to worry.
(I did, but screwed up my settings anyway)
posted by Acari at 9:22 AM on December 1
The most common cause of flaky Ethernet I've seen is bad patch cables. Seriously, how hard can it be to connect eight wires reliably to eight pins? And yet I've seen more failures in those than in any other kind of Ethernet-related gear. Keystone jacks where the wires have been stuffed into the punchdown connectors using pliers instead of a proper punchdown tool run a close second.
Next most common is switch damage due to current spikes induced in Ethernet cables by nearby lightning strikes. Sometimes it's just one port that gets taken out, sometimes the whole switch goes bad. I recently had to replace the D-Link DGS-1100-08 switch that links my place to the neighbours after a fairly intense storm; poor thing was so badly fried that after a factory reset it couldn't remember its own MAC address.
Another recent failure at my place turned out to be caused by a TP-Link powerline Ethernet adapter that had been installed next door for a year without previously having caused any trouble. I'd recently replaced our router but hadn't sorted out its UPS properly, and after a power outage the new router took maybe 10 seconds longer to boot up than the old one ever had. This provided a window of opportunity for the bastard TP-Link thing to probe the network for a DHCP server, decide it couldn't see one, and start up its own - which, because all my switches had already started up, caused all my connected devices to pick up bogus DHCP leases in completely the wrong address range.
Naturally, TP-Link describes this network-nobbling behaviour as "smart". Fixed by upgrading their firmware to a version that allows its DHCP server to be disabled entirely.
posted by flabdablet at 11:13 AM on December 1 [2 favorites]
Next most common is switch damage due to current spikes induced in Ethernet cables by nearby lightning strikes. Sometimes it's just one port that gets taken out, sometimes the whole switch goes bad. I recently had to replace the D-Link DGS-1100-08 switch that links my place to the neighbours after a fairly intense storm; poor thing was so badly fried that after a factory reset it couldn't remember its own MAC address.
Another recent failure at my place turned out to be caused by a TP-Link powerline Ethernet adapter that had been installed next door for a year without previously having caused any trouble. I'd recently replaced our router but hadn't sorted out its UPS properly, and after a power outage the new router took maybe 10 seconds longer to boot up than the old one ever had. This provided a window of opportunity for the bastard TP-Link thing to probe the network for a DHCP server, decide it couldn't see one, and start up its own - which, because all my switches had already started up, caused all my connected devices to pick up bogus DHCP leases in completely the wrong address range.
Naturally, TP-Link describes this network-nobbling behaviour as "smart". Fixed by upgrading their firmware to a version that allows its DHCP server to be disabled entirely.
posted by flabdablet at 11:13 AM on December 1 [2 favorites]
Fixed by upgrading their firmware to a version that allows its DHCP server to be disabled entirely.
Was expecting you to say "fixed by bashing the TP-Link to bits with a ball-peen hammer."
I think it's not a bad cable (since it goes out and stays out; it's not impossible, that's just a weird failure mode for cables). If the garage is on an internal network range, which one? And which one is your house on? There are 3 ranges that are typically used for private networks: 172.16.0.x, 192.168.x.x and 10.x.x.x.
If the garage range is the same as the rest of the house (i.e., not separate NAT regions) then you need to see where packets travel. Laptop or smartphone connected to garage network, some other regular computer on the house network, then see if you can ping from each to the other. Also check the IP (if any) handed out to the garage device. You're looking for unexpected behavior, i.e., if the garage network IPs become the wrong range when the time is up, it's probably that the switch has some kind of firmware bug or self-reset issue. In fact I'd check for firmware updates regardless. And disabling NAT/DHCP/other "smart" features in favor of, you know, classic switching will reduce your headaches overall.
General network troubleshooting is to start at the known-good part (your house network) and move toward the known-bad part, swapping one piece at a time and testing, until you discover the step in the chain where the fault exists. It's painstaking but it works. If you have a smartphone that can tether and the switch has wifi, you can try inserting it as the uplink for the switch (rather than the house network) and see if that restores connectivity, which would let you split the size of the problem domain roughly in half.
Finally, is it possible to (temporarily) put one of the garage devices on the house network? Just to see if routing around around the switch/garage network is a valid workaround. It would also confirm your suspicion that the problem is in the garage somewhere.
posted by axiom at 9:46 PM on December 1
Was expecting you to say "fixed by bashing the TP-Link to bits with a ball-peen hammer."
I think it's not a bad cable (since it goes out and stays out; it's not impossible, that's just a weird failure mode for cables). If the garage is on an internal network range, which one? And which one is your house on? There are 3 ranges that are typically used for private networks: 172.16.0.x, 192.168.x.x and 10.x.x.x.
If the garage range is the same as the rest of the house (i.e., not separate NAT regions) then you need to see where packets travel. Laptop or smartphone connected to garage network, some other regular computer on the house network, then see if you can ping from each to the other. Also check the IP (if any) handed out to the garage device. You're looking for unexpected behavior, i.e., if the garage network IPs become the wrong range when the time is up, it's probably that the switch has some kind of firmware bug or self-reset issue. In fact I'd check for firmware updates regardless. And disabling NAT/DHCP/other "smart" features in favor of, you know, classic switching will reduce your headaches overall.
General network troubleshooting is to start at the known-good part (your house network) and move toward the known-bad part, swapping one piece at a time and testing, until you discover the step in the chain where the fault exists. It's painstaking but it works. If you have a smartphone that can tether and the switch has wifi, you can try inserting it as the uplink for the switch (rather than the house network) and see if that restores connectivity, which would let you split the size of the problem domain roughly in half.
Finally, is it possible to (temporarily) put one of the garage devices on the house network? Just to see if routing around around the switch/garage network is a valid workaround. It would also confirm your suspicion that the problem is in the garage somewhere.
posted by axiom at 9:46 PM on December 1
I think it's not a bad cable (since it goes out and stays out; it's not impossible, that's just a weird failure mode for cables).
The way I've seen this kind of failure manifest before is that the flaky cable causes masses of lost packets. Most protocols will cope with that to some extent at the cost of slowing down, and with gigabit Ethernet that slowdown might not be noticed by a human for quite some while.
DHCP does not cope particularly well with high packet loss rates, and if it gets too slow then a lot of devices will just give up on it and auto-configure themselves with an IP address in the 169.254.0.0/16 block instead. This typically leaves them unable to communicate with other devices on the same LAN that did get an IP address via DHCP or static assignment, which usually includes the local Internet gateway.
posted by flabdablet at 7:49 AM on December 2
The way I've seen this kind of failure manifest before is that the flaky cable causes masses of lost packets. Most protocols will cope with that to some extent at the cost of slowing down, and with gigabit Ethernet that slowdown might not be noticed by a human for quite some while.
DHCP does not cope particularly well with high packet loss rates, and if it gets too slow then a lot of devices will just give up on it and auto-configure themselves with an IP address in the 169.254.0.0/16 block instead. This typically leaves them unable to communicate with other devices on the same LAN that did get an IP address via DHCP or static assignment, which usually includes the local Internet gateway.
posted by flabdablet at 7:49 AM on December 2
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1. Trying a different port on the first switch to rule out a flaky port.
2. Swapping out/re-terminating the ends of any keystone jacks/connectors in the flow to rule out a flaky termination?
posted by kbanas at 6:54 AM on December 1