Massive latency spikes with basic config

Installing and Using OpenWrt
1

Hi

I'm relatively inexperienced with OpenWrt and not sure how to go on about troubleshooting.

Flashed it on a ZBT WE826-t2 recently, and as I'm testing it, I notice that there are latency spikes, like BIG ones.

All this with latest version flashed and configuration almost untouched after reset.

Router wan port is connected to the modem lan.

Latency spikes are there with wired and wireless connection. None of these problems are present when connected directly to the modem.

This ping snippet is from SSH:

64 bytes from 1.1.1.1: seq=0 ttl=57 time=2.440 ms
64 bytes from 1.1.1.1: seq=1 ttl=57 time=3.400 ms
64 bytes from 1.1.1.1: seq=2 ttl=57 time=2.760 ms
64 bytes from 1.1.1.1: seq=3 ttl=57 time=3.020 ms
64 bytes from 1.1.1.1: seq=4 ttl=57 time=2.641 ms
64 bytes from 1.1.1.1: seq=5 ttl=57 time=3.140 ms
64 bytes from 1.1.1.1: seq=37 ttl=57 time=2101.435 ms
64 bytes from 1.1.1.1: seq=38 ttl=57 time=1101.248 ms
64 bytes from 1.1.1.1: seq=39 ttl=57 time=101.021 ms
64 bytes from 1.1.1.1: seq=40 ttl=57 time=2.700 ms
64 bytes from 1.1.1.1: seq=41 ttl=57 time=3.060 ms
64 bytes from 1.1.1.1: seq=42 ttl=57 time=2.840 ms
64 bytes from 1.1.1.1: seq=43 ttl=57 time=2.900 ms
64 bytes from 1.1.1.1: seq=44 ttl=57 time=2.700 ms
64 bytes from 1.1.1.1: seq=45 ttl=57 time=12.780 ms
64 bytes from 1.1.1.1: seq=46 ttl=57 time=2.940 ms
64 bytes from 1.1.1.1: seq=47 ttl=57 time=2.420 ms
64 bytes from 1.1.1.1: seq=78 ttl=57 time=2434.617 ms
64 bytes from 1.1.1.1: seq=79 ttl=57 time=1434.450 ms
64 bytes from 1.1.1.1: seq=80 ttl=57 time=434.183 ms
64 bytes from 1.1.1.1: seq=81 ttl=57 time=2.620 ms
64 bytes from 1.1.1.1: seq=82 ttl=57 time=2.900 ms
64 bytes from 1.1.1.1: seq=83 ttl=57 time=2.920 ms
64 bytes from 1.1.1.1: seq=84 ttl=57 time=2.860 ms
64 bytes from 1.1.1.1: seq=85 ttl=57 time=2.900 ms
64 bytes from 1.1.1.1: seq=86 ttl=57 time=3.180 ms
64 bytes from 1.1.1.1: seq=87 ttl=57 time=2.780 ms
64 bytes from 1.1.1.1: seq=88 ttl=57 time=3.320 ms

2

Try the following:

  1. Run the same test from OpenWrt (via an ssh session) and your ethernet connected compuer -- ideally at approximately the same time. This way we can see if the latency spikes are happening on OpenWrt+upstream, or if they are a downstream-only problem.
  2. Run ping tests against another site -- maybe openwrt.org or any other public site that returns pings. Does the problem remain (if not, it could be something with the cloudflare systems or configuration on their end).
  3. if you're still seeing the latency spikes on OpenWrt, try bypassing OpenWrt by using either another router entirely, or connecting your computer temporarily directly to your ISP (warning: make sure you have your firewall turned on since your computer will be directly exposed to the internet).
3

Modem (PON client) itself has a wifi. One laptop was connected to the modem wifi, another to openwrt router wifi. Latency spikes in Openwrt, smooth 46ms from modem itself.

The latency spikes affect everything. Websites don't respond during the spike, videos stop loading.

4

What is the subnet for that device's network? Is it, by chance, 192.168.1.0/24? If so, change your OpenWrt lan address to a different subnet (say 192.168.7.1 on the 192.168.7.0/24 network) so that it doesn't conflict.

1 Like
5

Thank you! That was the problem apparently.

Changed it and now everything runs smoothly.

6

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