I feel like I understand what I'm doing, but can't figure out why this isn't working.
ip address 192.168.254.254 255.255.255.0
ip address dhcp
global (Outside) 1 interface
nat (Inside) 1 192.168.254.0 255.255.255.0
nat (Outside) 1 192.168.100.0 255.255.255.0
static (Inside,Outside) tcp interface 5000 192.168.254.1 telnet netmask 255.255.255.255
access-group Outside_In in interface Outside
192.168.254.1 is a router. If I do a debug ip packet on 192.168.254.1, I can see the telnet session coming in - but the place I'm telnet'ing from never sees a response.