>I've inserted the following line in hosts.deny
>portmap: ALL

Make that:

ALL : ALL : spawn (/bin/mail root -s "%d - denied connect from %u@%h (%a)") &

That way, anytime a service is denied by tcp wrappers and email is sent off to root.

>and the following line in hosts.allow
>portmap: 192.168.100.0/255.255.255.0

You know that you can leave off the subnet mask and just say:

portmap : 192.168.100.

Same thing, just shorter format. What you have should work.

>The logged message is :
>samba mountd[366]: mount request from unknown host 192.168.100.3

Why is samba handling this? You may want to add an /etc/hosts entry, but since you are using ip's and not hostnames in your /etc/hosts.allow is shouldn't matter.

>My understanding is that allowing portmap services will give me access to nfsd and mountd.

You might have to explicity allow mountd and nfsd in your /etc/hosts.allow file. If you stick that ALL : ALL : spawn.... line in there, you will know for sure. If you get and email with the subject "mountd - denied connect..." then you know that you have to explicity allow it.

j