One of the certs I'm pursuing for fun is the CCNA, which I'll probably turn into the CCNA Security since that is more relevant to what I do as an infrastructure engineer.
I'm almost done with the first read through Lammle's book on the new CCNA exam and whereas I was somewhat noob-ish with networking stuff before (aside from TCP/IP, OSI, DNS, DHCP, etc) I've been getting deeper into switch/router/firewall configs and it all makes more sense now. I love it from a troubleshooting perspective and it's very, very helpful with everything server/virtualization/SAN related.
Recent problems solved:
Incorrect NAT's
Firewall ACL's listed out of order (firewall hitting explicit deny before evaluating ACL)
Cleaning up ASA config via service/network object groups
AAA group/VPN authentication failure (LDAP service account relocated in AD, thanks sys admin...)
GRE tunnel failure (backup primary datacenter route...!!!)
Stacked switch replacements (spotted improper MTU config required for end-to-end jumbo frames for the SAN's)
Rogue routes (was a wtf moment for a bit!)
Portfast not configured on CIO's new network drop
VLAN misconfigurations
There's a few others I can't recall but it's been such a big help furthering my ability to do just about everything with my own two hands since as an infra engi I do just that...everything! Also, whereas I used Wireshark/NetMon before for troubleshooting issues...it's my new best friend! Seriously
pcaps.
Along with the CCNA, looking forward to knocking out the VCP this fall...also will be upgrading my MCSA 2012 to MCSE for Server and probably Private Cloud. Looking forward to where things go from here
