If you are using private IPs for the host side of tap device
(eg. linux ubd0=... eth0=tuntap,,,192.168.11.11)
that do not resolve to names in DNS then telnet to the uml
from the host will take quite a bit of time (30sec).
So to solve this, add the host IP to the /etc/hosts in the uml fs.
This might go to the documentation.