Solved: pfSense Gateway Monitor Showing High Ping with T-Mobile Internet
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Hi, this has been an issue that has been bugging me for months, but it looks like I found the solution. I figured I'd post it with a nice descriptive title to make it easy to Google.
My T-Mobile Home Internet has been showing 10000ms+ latency in pfSense's dpinger gateway monitoring for the last several months, and I had to disable the gateway monitoring action in order to have failover function at all. Annoyingly, pinging the same IP from Diagnostics -> Ping showed a reasonable ~30ms response time. However, looking at a packet capture of the interface, it was showing that the responses to dpinger's echo requests were legitimately being received ~10000ms later.
It appears that T-Mobile is doing some kind of shenanigans or deprioritization of small ICMP packets. While a standard ping uses a larger payload, dpinger uses a payload of 1 by default to reduce bandwidth usage. To solve this, we just need to make our packets bigger.
The Fix:
In System -> Routing, click edit on your T-Mobile gateway. At the bottom, click "Display Advanced". Under "Data Payload", set the value to something bigger. I'm using a value of 10 and it seems to be working, but smaller values may be sufficient. After making this change, I'm now seeing the gateway latency being reported at ~30ms. Yay!
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Interesting. It must be a local configuration in the T-Mobile network where you live. I get dpinger responses in the 30ms range with the default payload but occasionally get duplicate ping responses.
Last year I would get dozens of duplicate responses per day but these days I get a few per week.
I wonder if a larger payload would stop the duplicates. I might try an experiment and see.
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said in Solved: pfSense Gateway Monitor Showing High Ping with T-Mobile Internet:
Interesting. It must be a local configuration in the T-Mobile network where you live. I get dpinger responses in the 30ms range with the default payload but occasionally get duplicate ping responses.
Last year I would get dozens of duplicate responses per day but these days I get a few per week.
I wonder if a larger payload would stop the duplicates. I might try an experiment and see.
Almost a week now without a duplicate-ping error. More support that this added payload length addresses that problem too.
I'd be interested to understand T-Mobile's reasoning to do some of the seemingly crazy non-standard network architecture things...but alas I probably never will.
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@Mission-Ghost Glad to see it's helping with other issues too. I have no clue why they do the things that they do, it makes no sense to me either, but for the low cost of their backup internet service, I'm happy to have the redundancy. They've been doing a lot of new construction in my area, and my main connection has been having more trouble than ever.
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They probably do it so small packets get de-prioritized in the netwrk, and don't adversely load the router cpu. Remember router throughput is a combination of max bandwidth & total packets per second. If they hit the PPS limit at low bandwidth, then the overall throughput is impacted.
Should not be an issue with modern routers, but the guys that configure it, may simply be cautious ?
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P patient0 referenced this topic
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At times t-mobile drops icmp with length less than 4. A temp fix is to edit /etc/inc/gwlb.inc and change the default from 1 byte to 4.