Strange SNMP problem in Ubuntu or other platform

Description of the problem:
After I have installed SNMPd in Ubuntu 9.04, I was trying to snmpwalk system to test the correction of the installation and deployment. However, I got a Time out message even though I did not get any firewall installed in Ubuntu. At the beginning, I thought that it is the firewall problem like in Fedora. The truth of no firewall installed in Ubuntu by default makes me realise that this is not in that case.

Solution:
Ubuntu is different from Fedora, there is a file to keep the default snmpd's running options, which is:
/etc/default/snmpd. In it, the options denote that only local host is able to snmpwalk the SNMP agent. In this case, I will not only need to change the snmpd.conf configure file, but I will also need to change some lines in the snmpd configure file mentioned above to make it work. The changing is like this:

#SNMPDOPTS='-Lsd -Lf /dev/null -u snmp -I -smux -p /var/run/snmpd.pid 127.0.0.1'
SNMPDOPTS='-Lsd -Lf /dev/null -u snmp -I -smux -p /var/run/snmpd.pid -c /etc/snmp/snmpd.conf