This guide does a great job explaining how ssh-agent works across multiple systems. I'd like to get forwarding set up as it is in the last set of diagrams, but I'm having trouble tracking down the steps required to do so.
For some machines on my network, I can ssh from A to B, then B to C, without ever entering a cert password. Other machines, however, give a "Could not open a connection to your authentication agent" (sometimes!), then won't forward my authentication info. SSHing from one of these machines to another box on the network prompts for my private-key password again.
I didn't build these machines, but I can administer some of them. I don't know for sure what the difference is between boxen that work and the ones that don't -- could be a firewall issue, ssh/ssh-agent/sshd configuration, anything, and I don't see any step-by-step guides specific to forwarding floating around the 'net. I just need to know where to start chasing this issue down.