The benefits of growing your toolbox
Although we weren't going to use our new gigabit backbone connection immediately, I wanted to check that we really could get something close to gigabit performance through it and that everything was working smoothly. When you're doing network performance testing, you really need to do it from a platform that you trust, so that any slowness can be attributed to the stuff in the middle and not to your end having issues.
As it happened, the most trustworthy machine for this was my office workstation. But since it was my workstation, I didn't want to disconnect it from its regular home in order to do testing, which meant that I needed a way to force the gigabit test traffic to flow over the interface connected to the touchdown switch and not, say, over the regular default route's interface (which would go out our 100 mbit backbone connection); fortunately I already knew how to do that.
Since I looked into the dual identity routing issues purely for my own use, this makes a great illustration of the benefits of growing your toolbox; working out how to set up my own home VPN gave me the tools I needed to easily test a new gigabit backbone connection at work.
This has become a relatively common thing for me; over and over again I've found myself applying the results of earlier curiosity to practical problems that have come up at work. Knowing more, even if it initially seems irrelevant, has made me a better system administrator.
(It helps if you're an intellectual magpie and take delight just in learning cool stuff. Then any future payoffs are just a surprise bonus and it's not work to do the scavenging.)