Meatballs
New Around Here
[This seemed to work for a bit - then after a reconnect I started getting the same error again... further diagnosis/tweaks required]
I have just had to diagnose an issue with new Pixel 3 running Android Pie (9). All my other devices have worked flawlessly with my router but I was having connectivity issues to specific endpoints (Facebook app, Google OAUTH pages etc). I thought I would document symptoms and resolution here incase anyone else hits the problem and save them some hours.
Symptoms:
Web browsing works fine for most hosts (google.co.uk worked - google.com failed to load), speed tests all execute correctly. However, my facebook app feeds wouldn't load at all, and attempting to login to apps like Phillips Hue with my Google account would result in a page that fails to load.
Diagnosis:
Installed tcpdump on the router. I noticed a lot of "ICMP ip reassembly time exceeded, length 556" errors from 1e100 (google) DNS hosts to my Android 9 device.
My ISP's WAN device (4G LTE broadband) has an MTU size of 1400.
My Asuswrt
RT-AC3200 had been working fine with around 20-30 existing devices without setting the WAN > Special Requirement from ISP > WAN MTU.
Fix:
Set the WAN MTU to 1400. (or whatever your broadband MTU is). You can manually check this from Windows ping command e.g.:
ping -l 1372 -f 8.8.8.8
Pinging 8.8.8.8 with 1372 bytes of data:
Reply from 8.8.8.8: bytes=1372 time=34ms TTL=118
ping -l 1373 -f 8.8.8.8
Pinging 8.8.8.8 with 1373 bytes of data:
Reply from 192.168.0.1: Packet needs to be fragmented but DF set.
(Ping ICMP header is 28 bytes so add that to the -l value = 1400/1401).
I'm not sure whats special about Android 9 - maybe tcp_mtu_probing is disabled or something.
I have just had to diagnose an issue with new Pixel 3 running Android Pie (9). All my other devices have worked flawlessly with my router but I was having connectivity issues to specific endpoints (Facebook app, Google OAUTH pages etc). I thought I would document symptoms and resolution here incase anyone else hits the problem and save them some hours.
Symptoms:
Web browsing works fine for most hosts (google.co.uk worked - google.com failed to load), speed tests all execute correctly. However, my facebook app feeds wouldn't load at all, and attempting to login to apps like Phillips Hue with my Google account would result in a page that fails to load.
Diagnosis:
Installed tcpdump on the router. I noticed a lot of "ICMP ip reassembly time exceeded, length 556" errors from 1e100 (google) DNS hosts to my Android 9 device.
My ISP's WAN device (4G LTE broadband) has an MTU size of 1400.
My Asuswrt
RT-AC3200 had been working fine with around 20-30 existing devices without setting the WAN > Special Requirement from ISP > WAN MTU.
Fix:
Set the WAN MTU to 1400. (or whatever your broadband MTU is). You can manually check this from Windows ping command e.g.:
ping -l 1372 -f 8.8.8.8
Pinging 8.8.8.8 with 1372 bytes of data:
Reply from 8.8.8.8: bytes=1372 time=34ms TTL=118
ping -l 1373 -f 8.8.8.8
Pinging 8.8.8.8 with 1373 bytes of data:
Reply from 192.168.0.1: Packet needs to be fragmented but DF set.
(Ping ICMP header is 28 bytes so add that to the -l value = 1400/1401).
I'm not sure whats special about Android 9 - maybe tcp_mtu_probing is disabled or something.
Last edited:
