How we spent a full day figuring out a MTU issue with docker

Background

High level debugging

ldapsearch -d 1 -vv -x -LLL -H ldap://10.10.0.10 -D  'CN=root,CN=Users,DC=Project,DC=domain,DC=com' -b 'DC=Project,DC=domain,DC=com' -W 2>&1 | less

Low level debugging

Capture of request sent from my host — working
Capture from request sent from a Docker Container — Failed

The Bug

$ ifconfig | grep ppp0
ppp0: flags=4305<UP,POINTOPOINT,RUNNING,NOARP,MULTICAST> mtu 1400

Solution

networks:
backend:
driver: bridge
driver_opts:
com.docker.network.driver.mtu: 1400

AWS Solutions Architect at National Bank of Canada — https://sylwit.com