Tag Archives: dns

Ubuntu 8.10 Intrepid – Fix Static IP & Network Manager Problem

Hey all,

today i have installed the new release of Ubuntu, 8.10 Intrepid

but i had a problem setting my IP to a static one, when i do this through the network manager, and when i edited the network files manually nothing worked, so here is the steps i followed to solve the problem :

first i removed the network manager

sudo update-rc.d -f NetworkManager remove

then i added my network configuration by editing the file /etc/network/interfaces

sudo gedit /etc/network/interfaces

so it looks like

auto lo
iface lo inet loopback
auto eth0
iface eth0 inet static
address 192.168.1.xxx
netmask 255.255.255.0
network 192.168.1.0
broadcast 192.168.1.255
gateway 192.168.1.xxx

then i edited the file /etc/resolv.conf to add my DNS

sudo nano -w /etc/resolv.conf

to look like

# Generated by NetworkManager
nameserver 192.168.1.xxx

then i restart the networking by :

sudo /etc/init.d/networking restart

if u still have problems, i suggest you restart the machine and check, the above steps is how i got my network up .

enjoy the new Ubuntu ;)

Mail System @ Office is back 2 life again.

Recently we had this problem in the company, our mails doesn’t reach some of the recipients,

after analyzing the situation, i discovered that we have 2 problems :

1- Our forward and reverse DNS doesn’t match

check the error from DnsStuff.com when i test the reverse DNS on our mail server :

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Location: Egypt (high) [City: Cairo, Al Qahirah]Preparation:The  reverse DNS entry for an IP is found by reversing the IP, adding it to "in-addr.arpa", and looking up the PTR record.So, the reverse DNS entry for 217.52.xx.xxx is found by looking up the PTR record forxxx.xx.52.217.in-addr.arpa.
 
All DNS requests start by asking the root servers, and they let us know what to do next.
 
See How Reverse DNS Lookups Work for more information.
 
How I am searching:
 
Asking g.root-servers.net for xxx.xx.52.217.in-addr.arpa PTR record:
 
g.root-servers.net says to go to sec1.apnic.net. (zone: 217.in-addr.arpa.)
 
Asking sec1.apnic.net. for xxx.xx.52.217.in-addr.arpa PTR record:
 
sec1.apnic.net [202.12.xx.xx] says to go to ns2.xxxx-online.net. (zone: 52.217.in-addr.arpa.)
 
Asking ns2.nile-online.net. for xxx.xx.52.217.in-addr.arpa PTR record:  Reports mail.xxx-xxxxxxxxxxxxx.com. [from 62.140.73.2]
 
Answer:
 
217.52.xx.xxx PTR record: mail.xxx-xxxxxxxxxxxxx.com. [TTL 86400s] [A=CNAME] *ERROR* A record for mail.xxx-xxxxxxxxxxxxx.com. does not point back to original IP.  RFC1912 2.1 disallows CNAMEs.
 
To see the reverse DNS traversal, to make sure that all DNS servers are reporting the correct results, you can Click Here.

2- We don’t have any reference for the server in the office that we use to send direct emails in the MX Records of our domain, which makes some server doesn’t trust our emails.

Check the headers of emails from gmail when we had the problem :

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Received-SPF: neutral (google.com: 217.52.xx.xxx is neither permitted nor denied by best guess record for domain of ahmed@xxx-xxxxxxxxxxxx.com) client-ip=217.52.xx.xxx;Authentication-Results: mx.google.com; spf=neutral (google.com: 217.52.xx.xxx is neither permitted nor denied by best guess record for domain of ahmed@xxx-xxxxxxxxxxxx.com) smtp.mail=ahmed@xxx-xxxxxxxxxxxx.com

I solved the 2 problems by following the next steps:

1- Created A record mailer1.xxx-xxxxxxxxxxxx.com to point to our mail server IP 217.52.xx.xxx

2- Created MX record for the A record previously created.

3- Contacted our ISP to change the reverse DNS / PTR to reply with mailer1.xxx-xxxxxxxxxxxx.com for any reverse lookup.

Now after 24 hours everything seems working perfectly,

check the reverse lockup results from DnsStuff.com :

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Location: Egypt (high) [City: Cairo, Al Qahirah]
 
Preparation:
The  reverse DNS entry for an IP is found by reversing the IP, adding it to "in-addr.arpa", and looking up the PTR record.
So, the reverse DNS entry for 217.52.xx.xxx is found by looking up the PTR record for
 xxx.xx.52.217.in-addr.arpa.
All DNS requests start by asking the root servers, and they let us know what to do next.
See How Reverse DNS Lookups Work for more information.
 
How I am searching:
Asking i.root-servers.net for xxx.xx.52.217.in-addr.arpa PTR record:
       i.root-servers.net says to go to ns3.nic.fr. (zone: 217.in-addr.arpa.)
Asking ns3.nic.fr. for xxx.xx.52.217.in-addr.arpa PTR record:
       ns3.nic.fr [192.134.x.xx] says to go to ns2.nile-online.net. (zone: 52.217.in-addr.arpa.)
Asking ns2.nile-online.net. for xxx.xx.52.217.in-addr.arpa PTR record:  Reports mailer1.xxx-xxxxxxxxxxxx.com. [from 62.140.xx.x]
 
Answer:
217.52.31.189 PTR record: mailer1.cha-international.com. [TTL 86400s] [A=217.52.xx.xxx]

and the headers of our emails from gmail.

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Received-SPF: pass (google.com: best guess record for domain of ahmed@xxx-xxxxxxxxxxxx.com designates 217.52.xx.xxx as permitted sender) client-ip=217.52.xx.xxx;
Authentication-Results: mx.google.com; spf=pass (google.com: best guess record for domain of ahmed@xxx-xxxxxxxxxxxx.com designates 217.52.xx.xxx as permitted sender) smtp.mail=ahmed@xxx-xxxxxxxxxxxx.com

I hope this would be useful for you as it was for me, have a nice mail ;)