Question Strange network outages

Aug 20, 2019
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I have a strange thing happen, often, and its bugging me.

setup:

3 PCs all hard wired tp switch (to-link - but have tried a dlink and netgear as well same thing happens)
192.168.5 . 2,3,4
dsl modem/router comes off said switch (which also has wifi, makes no difference if a laptop is connected with wifi, or no devices on wifi)
192.168.5.1

if router goes out 192.168.5.2 times out talking to .3 or .4

possibly related: if .3 is sending out to internet occupying all my upstream (1mb/s) the LAN becomes horribly slow, .2 to .3 or 3 to .4, whatever
even though the LAN is gbit. even though the LAN has local DNS cache server ( with local machiens in a zone so does not require internet access to look up local pc domain)

curious if someone knows the causes/fixes?
 

Lutfij

Titan
Moderator
Seems like your ISP is the limiting factor. In any case, make sure you router is on the latest firmware. Likewise make sure your system's all have the latest networking drivers and that they're also on the same OS environment(if Windows 10).
 

Ralston18

Titan
Moderator
Are those the actual IP addresses or just "reference numbers" for PC's 2, 3, & 4?

Static or DHCP IP addresses? If static are those addresses reserved for each PC via the respective PC's MAC?

And, as I understand your post, the DSL connection comes into the modem/router. Make and model?

Then via LAN port or WAN port on the modem router is connected to a port on the switch via an Ethernet cable. (Modem/router: make = TP-Link, model = ? Verify.)

Next three of the other LAN ports on the switch are connected to serve the 3 PCs via Ethernet cables.

Are you able to provide a simple sketch or connection diagram? Be sure to note if the connected ports are WAN or LAN.
 
Aug 20, 2019
4
0
10
0
Seems like your ISP is the limiting factor. In any case, make sure you router is on the latest firmware. Likewise make sure your system's all have the latest networking drivers and that they're also on the same OS environment(if Windows 10).
No.

This is for internal traffic so its something not related to ISP
 
Aug 20, 2019
4
0
10
0
Are those the actual IP addresses or just "reference numbers" for PC's 2, 3, & 4?

Static or DHCP IP addresses? If static are those addresses reserved for each PC via the respective PC's MAC?

And, as I understand your post, the DSL connection comes into the modem/router. Make and model?

Then via LAN port or WAN port on the modem router is connected to a port on the switch via an Ethernet cable. (Modem/router: make = TP-Link, model = ? Verify.)

Next three of the other LAN ports on the switch are connected to serve the 3 PCs via Ethernet cables.

Are you able to provide a simple sketch or connection diagram? Be sure to note if the connected ports are WAN or LAN.

Think of it this way, 3 pc's all using static private address space ipv4, all wired to a switch
they all communicate fine with each other, a dsl router billion 8700axl (also has been 7800, a dlink and netgear) is also connected, just like the pc's except its the def GW.
the switch is a tp-link sg1024d

now if the router has internet, everyone on LAN still talks to others on LAN.
but if the router is rebooting or off or whatever, PC's on the LAN cant talk to each other, even by pure IP, eliminating DNS. one of these machines is also Linux.

I guess, is it possible for the router (which also has 4 port switch -UNUSED) is squashing the arp cache or whatever it is the switch uses that says hey port 2 goto port 19 for that IP, because my way of thinking is that switch does all the internal traffic, unless something goes out the internet of course.
 

Ralston18

Titan
Moderator
The switch does not route network traffic.

If the router is off, rebooting, or otherwise occupied then the PC's on the network will not be able to talk with each other. Network communications are the responsibility of the router.

I.e., keep track of the respective computer's IP addresses (static or otherwise) according to the MAC of the applicable network adapter. Then manage the network traffic between connected devices accordingly. I.e., which computer/device is sending and who is to receive that communication.

The switch is basically just a device that provides more ports - the switch does not manage the network traffic; i.e., "unmanaged".

Managed switches are generally not needed for home use. They do provide some other features and functions but they do not do routing.

FYI:

https://www.windowscentral.com/should-you-buy-managed-or-unmanaged-switch

https://planetechusa.com/blog/do-i-need-a-managed-switch-for-my-smart-home-network/

My sense is that you are thinking in terms of a peer to peer relationship between the networked devices. The switch does not do that.
 
Aug 20, 2019
4
0
10
0
The switch does not route network traffic.

If the router is off, rebooting, or otherwise occupied then the PC's on the network will not be able to talk with each other. Network communications are the responsibility of the router.

I.e., keep track of the respective computer's IP addresses (static or otherwise) according to the MAC of the applicable network adapter. Then manage the network traffic between connected devices accordingly. I.e., which computer/device is sending and who is to receive that communication.

The switch is basically just a device that provides more ports - the switch does not manage the network traffic; i.e., "unmanaged".

Managed switches are generally not needed for home use. They do provide some other features and functions but they do not do routing.

FYI:

https://www.windowscentral.com/should-you-buy-managed-or-unmanaged-switch

https://planetechusa.com/blog/do-i-need-a-managed-switch-for-my-smart-home-network/

My sense is that you are thinking in terms of a peer to peer relationship between the networked devices. The switch does not do that.

HUH, no I know the router routes traffic, but a switch knows when everything is local, even dumb switches know it has a MAC address table to IP so it knows what is local, even I know that much, because in trying to nut this out I segmented the LAN, tp-link dw, router and pc3 (server) in garage, the other two pc's (1&2) in my study now have another dumb switch a cheap 20 dollar ebay tenda thing and it knows what is local to it, pc1 to pc2 no problems, I can rip that port that goes to man switch out and they still happily talk to each other.
ping flood pc1 to pc2 - cheapy tenda sw leds for ports that pcs 1 & 2 are ongo berserk, port 8 the link to wall going to main tp-link sw, does not see that traffic by its led status, if I ping flood pc3 (server) from pc1, the led light on pc2 cheapy sw doest do much. but the port for Pc1 and the leds on tp-link for pc3 go berserk

I might need to find a specialist networking forum i think, thanks anyway.
 
A switch has no concept of ip addresses. That is what make a device a switch or a router..ignoring some fancy commercial switches.

There are no arp tables in switch there is only a table that maps what port a mac address was last seen on.

Your end devices are doing all the work maping IP to mac. Even if you have a router when you talk to other devices the router is not involved.

The way it works is the pc sees if it has a entry for the ip in it ARP table. If not it send a ARP to the broadcast mac address. The switch then sends this to all ports. The end device gets the ARP and responds sending a message directly to the mac address of the machine that issues the ARP. Many times this responding machine will also make a entry in its ARP table mapping the other ip and mac. As these message were passing the switch kept track of which mac addresses where on which port.

After this all packets are send to the mac addresses. There maybe ip in the packets but they are not used for path selection only the mac addresses are used.

This almost sounds like you have a subnet mask wrong on some device. If you put 255.255.255.255 all the traffic is proxied via the router.....some routers do not support this because it is not a recommended configuration.

Otherwise I would be looking for duplicate IP addresses. Look at the arp tables in the pc and see what mac addresses they map to when it functions and when it does not.
 

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