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Linux: Receiving HTTP 408 Errors Installing JumpCloud Agent on Amazon EC2

Problem Description

After installing the JumpCloud Agent using the curl command to a Linux Amazon EC2 hosted system, the agent will fail to start and will report the following within /var/log/jcagent.log:
2016/02/02 19:11:04 [9762] Initial certificate checks failed, err='Could not seal the agent to JumpCloud, err='Could not initialize client certificate, err='Could not sign the certificate, err='CSR request failed with status=408, body='<html><body><h1>408 Request Time-out</h1> 
Your browser didn't send a complete request in time. 


The problem involves improper packet splitting. When Amazon identifies an internal instance, it sets the MTU to 9001(jumbo frames). However, outbound traffic is still set to an MTU of 1500. The default version of curl was not properly reading the correct MTU, and was thus attempting to send a 9001 size frame, but only the first 1500 chars were actually copied.

On the Linux instance run:

ifconfig <interface> mtu 1500 up

You may also make a permanent change in /etc/sysconfig/network-scripts/ifcfg-<interface> by adding MTU=1500

Last Updated: Feb 21, 2018 01:55PM MST

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