Testing Reverse DNS Lookup

[dlopez@hostname ~]$ *dig mail-relay.prod.domain.com. +nocomments | egrep “NS|A”*
;mail-relay.prod.domain.com. IN A
mail-relay.prod.domain.com. 6 IN A IPAddress
domain.com. 86138 IN NS pdns1.ultradns.net.
domain.com. 86138 IN NS pdns5.ultradns.info.
domain.com. 86138 IN NS pdns2.ultradns.net.
domain.com. 86138 IN NS pdns4.ultradns.org.
domain.com. 86138 IN NS pdns6.ultradns.co.uk.
domain.com. 86138 IN NS pdns3.ultradns.org.
pdns1.ultradns.net. 1360 IN A
pdns1.ultradns.net. 1360 IN AAAA 2001:502:f3ff::1
pdns2.ultradns.net. 772 IN A
pdns3.ultradns.org. 3252 IN A
pdns4.ultradns.org. 3252 IN A
pdns4.ultradns.org. 3252 IN AAAA 2001:502:4612::1
pdns5.ultradns.info. 2412 IN A
pdns6.ultradns.co.uk. 120 IN A
;; WHEN: Mon Apr 9 20:00:02 2012
[bfisher@hostname ~]$ *dig -x IPAddress +nocomments | egrep “NS|PTR”*
;IPAddress.in-addr.arpa. IN PTR
IPAddress.in-addr.arpa. 65939 IN PTR mail-relay.prod.domain.com.
IPAddress.in-addr.arpa. 65939 IN NS pdns4.ultradns.org.
IPAddress.in-addr.arpa. 65939 IN NS pdns1.ultradns.net.
IPAddress.in-addr.arpa. 65939 IN NS pdns3.ultradns.org.
IPAddress.in-addr.arpa. 65939 IN NS pdns6.ultradns.co.uk.
IPAddress.in-addr.arpa. 65939 IN NS pdns5.ultradns.info.
IPAddress.in-addr.arpa. 65939 IN NS pdns2.ultradns.net.
[dlopez@hostname ~]$

You can also check http://www.mxtoolbox.com/SuperTool.aspx and type in IPAddress

Check for Blacklisting

Check http://www.mxtoolbox.com/SuperTool.aspx click the Blacklists tab and enter IP address.

Enable SSH on Fedora 16

Enable sshd service.

$ systemctl enable sshd.service
start sshd service

$ systemctl start sshd.service
check sshd status if needed.

$ systemctl status sshd.service
restart sshd service, when needed.

$ systemctl restart sshd.service
stop sshd service and duck down

$ systemctl stop sshd.service
well, make sure you have port 22 open.

$ system-config-firewall