Find and Fix Network Loops

Network loops are bad news.

Here’s a recap from network engineer Ethan Banks on why:

In a network, a loop provides a never-ending path for network traffic to follow. In Ethernet, frames never die; there’s no time-to-live function attached to a traditional Ethernet frame. Therefore, if a loop exists, frames with no explicit destination (like broadcast frames) circle around the network forever.

As broadcast frames accumulate, the negative impact on the network increases. Broadcast frames are meant for everyone on the segment; every attached host must process the broadcast. Over and over again. In increasing volume over time. For this reason, bridging loops are sometimes called broadcast storms.

These storms impact network utilization and take up CPU resources. Network switches and routers are heavily impacted by these storms; their CPUs spike up to 100% utilization in seconds due to all the broadcast processing they must handle. This often prevents them from doing other things they should be doing, like maintaining the spanning-tree topology or keeping up with their routing neighbors. The end result is a network outage.

Client down!

So finding and fixing network loops quickly is important. But one of the biggest problems with loops, as engineer Kevin Dooley explains, is that when the entire network becomes unusable, you often can’t log into the switches to manually dig into what’s wrong.

Not to mention, manual investigation can take many days—because when the network goes down, you may not even know that a loop is a culprit.

Unless you have Auvik.

Auvik automatically alerts you to Layer 2 loops if you have spanning tree enabled on your core and access switches.

Auvik can also identify broadcast storms. A preconfigured alert tells you when a significant percentage of a switch port’s traffic is broadcast as opposed to unicast or multicast. You can lower the threshold of this alert for sensitive or troubleshooting scenarios to be more proactive and in the know.

No more tearing your hair out at network loops

Jake Bloedow of Thriveon explains how Auvik helped him identify a loop as the culprit of a network performance issue in two hours—versus more than 70 hours that a competing MSP had spent debugging the issue with no success.

“We had a prospect that was having network trouble. They had another MSP there for about a week, spending 14 to 16 hours a day trying to fix the problem. We deployed Auvik at 4 p.m. By 5:30, we looked at the network map, saw there were two loops in the environment. Called the client at 6:00, had them unplug the two loops, and they were fixed.”

Corey Kirkendoll, CEO at 5K Technical Services, had a client who struggled for two days without Auvik in a similar scenario.

“Someone came into a client’s network, plugged in a switch, and created a loop in the network. It took them two days to find that loop. They couldn’t figure it out, they didn’t know what to do. The only way the network stabilized was that the person who plugged in the switch came and unhooked it again. He had no idea he’d caused that issue. I told the prospect if they had what we’re working with, we would have just seen it. Auvik would have picked it up and shown us. It wouldn’t have taken two days.”

Network loops are one of those things that can have you tearing your hair out for days, burning through billable hours while your client broods about a network outage.

With Auvik, network loops need never be an issue.