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Forum Discussion
Orbi Ethernet Backhaul causing broadcast storm
I have just upgraded my Orbi router and satellites to V2.1.1.12 hoping to take advantage of the recent Ethernet backhaul feature. I use the Orbi router as my main router with a 24 port switch servic...
Understand. However I also have non Orbi devices connected to the in between switch on my system. Only issues I saw when a storm happend was a IP address conflict. Setting up an IP address reservation helped resolve this. Something to look out for in this kind of configuration. Non managed switches work well in between and hind the satellites along with non connected devices. Just make sure the IP addresses are good and reserved.
FURRYe38 wrote:
Understand. However I also have non Orbi devices connected to the in between switch on my system. Only issues I saw when a storm happend was a IP address conflict. Setting up an IP address reservation helped resolve this. Something to look out for in this kind of configuration. Non managed switches work well in between and hind the satellites along with non connected devices. Just make sure the IP addresses are good and reserved.
The IP address conflicts are caused by the broadcast storm not the other way around. The root cause is that ARP packets (which are broadcast) are being dropped by the network. When a device can't use ARP to find other devices on the network, it gives up and tries to get another IP address from the DHCP server. Since the DHCP server also uses ARP (which is still broken) to find other devices on the network there is no way for the DHCP server to prevent IP address conflicts. DHCP reservations give the DHCP server an alternative method to avoid duplicate IP addresses, but it does nothing to solve the ARP storm which broke the network in the first place.
An ARP storm is created when you have a duplicate link between network segments. In my case, I already had an ethernet cable linking two rooms in my house. Each room had a switch so I could connect multiple wired devices to the same cable. When I added an Orbi to each room the Orbi's backhaul (either ethernet or wireless) added the second duplicate link.
When a device transmits a broadcast packet (like ARP) in one room, it must be forwarded to the other room over the long ethernet cable. Since I have both the Orbi's and the switches connecting the two rooms the broadcast packet gets forwarded twice, by both the Orbi and also by the switch. The problem begins when those two packets get to the other room. Since there are two links the packet sent to the Orbi is forwarded to the switch and the packet sent to the switch is forwarded to the Orbi creating a loop. This loop only kills broadcast traffic, but as you saw above traffic like ARP is pretty important to a network.
The fix is to eliminate the redundant link. Since we want to use the Orbi's ethernet backhaul we need to make sure the two rooms can't also talk to each other through a switch.
I fixed my problem by unplugging the long ethernet cable from the switches and connecting it directly to my two Orbis. I then connected the switches to a different ethernet port on each Orbi. Now there is only one path between my rooms. Everything flows through the Orbi and the broadcast storms are gone.
Interesting. Will keep this in mind. Well from what I saw maybe this was the case. However after getting my devices set up for reserved IPs, at least the two offending devices that seem to have a problem during the storm I saw, the satellite and my cell phone microcell, Once these were disconnected from the network and rejoined one at a time and give an IP address reservation, with the two switches in between, I haven't seen a storm since. So I just figured that these two devices along with a problem at the DHCP server ON the router had generated this storm I saw. I'll besure to keep this in mind for next time and for others. This is good information and hopefully NG will take heed on it. I do feel that there is a problem in the DHCP services in Orbi.
Can one of the forum moderators pass this along to NG engineering please for review?
BubbaDoug wrote:
FURRYe38 wrote:
Understand. However I also have non Orbi devices connected to the in between switch on my system. Only issues I saw when a storm happend was a IP address conflict. Setting up an IP address reservation helped resolve this. Something to look out for in this kind of configuration. Non managed switches work well in between and hind the satellites along with non connected devices. Just make sure the IP addresses are good and reserved.
The IP address conflicts are caused by the broadcast storm not the other way around. The root cause is that ARP packets (which are broadcast) are being dropped by the network. When a device can't use ARP to find other devices on the network, it gives up and tries to get another IP address from the DHCP server. Since the DHCP server also uses ARP (which is still broken) to find other devices on the network there is no way for the DHCP server to prevent IP address conflicts. DHCP reservations give the DHCP server an alternative method to avoid duplicate IP addresses, but it does nothing to solve the ARP storm which broke the network in the first place.
An ARP storm is created when you have a duplicate link between network segments. In my case, I already had an ethernet cable linking two rooms in my house. Each room had a switch so I could connect multiple wired devices to the same cable. When I added an Orbi to each room the Orbi's backhaul (either ethernet or wireless) added the second duplicate link.
When a device transmits a broadcast packet (like ARP) in one room, it must be forwarded to the other room over the long ethernet cable. Since I have both the Orbi's and the switches connecting the two rooms the broadcast packet gets forwarded twice, by both the Orbi and also by the switch. The problem begins when those two packets get to the other room. Since there are two links the packet sent to the Orbi is forwarded to the switch and the packet sent to the switch is forwarded to the Orbi creating a loop. This loop only kills broadcast traffic, but as you saw above traffic like ARP is pretty important to a network.
The fix is to eliminate the redundant link. Since we want to use the Orbi's ethernet backhaul we need to make sure the two rooms can't also talk to each other through a switch.
I fixed my problem by unplugging the long ethernet cable from the switches and connecting it directly to my two Orbis. I then connected the switches to a different ethernet port on each Orbi. Now there is only one path between my rooms. Everything flows through the Orbi and the broadcast storms are gone.
Thank you Sir.
Christian_R wrote:
Enginnering is aware and working on resolving these issues in future firmwares
~Christian
