Configuring and Managing MPE/iX Internet Services (August 2002)

Chapter 8
DNS BIND/iX
DNS and Electronic Mail
133
hpmdd58.india.hp.com. 1D IN A 15.70.168.58
palsmtp.hp.com. 8H IN A 156.153.255.242
palsmtp.hp.com. 8H IN A 156.153.255.226
atlsmtp.hp.com. 8H IN A 156.153.255.210
atlsmtp.hp.com. 8H IN A 156.153.255.202
quasar.india.hp.com. 1D IN A 15.10.45.114
cauvery.india.hp.com. 1D IN A 15.10.40.5
valmiki.india.hp.com. 1D IN A 15.17.112.100
sahana.india.hp.com. 1D IN A 15.10.43.22
NOTE In order to run the various utilities, you will need to modify your PATH variable, adding the
following two directories:
/BIND/PUB/sbin
/BIND/PUB/bin
DNS and Electronic Mail
One of the advantages of the Domain Name System over host tables is its support of advanced mail routing.
DNS offers a mechanism for specifying backup hosts for mail delivery. The mechanism also allows hosts to
assume mail handling responsibilities for other hosts. This lets diskless workstations that don’t run mailers,
for example, have mail addressed to them processed by their server. These features give administrators more
flexibility in configuring electronic mail on their network.
MX Records
DNS uses a single type of resource record to implement enhanced mail routing, the MX record. MX records
specify a mail exchanger for a domain name, a host that will either process or forward mail for the domain
name.
In order to prevent mail routing loops, the MX record has an extra parameter, besides the domain name of the
mail exchanger, a preference value like: peets.mpk.ca.us IN MX 10 relay.hp.com specifies that
relay.hp.com is a mail exchanger for peets.mpk.ca.us at preference value 10.
DNS BIND Troubleshooting Steps
1. Resources: Find a resource who is experienced with DNS BIND/iX! If you’re entering into this without
DNS BIND/iX experience, you’re off to a difficult start. Problems with this product are generally caused
by poor configuration, so it’s critical to have a DNS BIND literate engineering resource available for
problem classification and management.
2. Check the Obvious: Those with experience in DNS BIND troubleshooting will have built up a number
of quick “sanity checks” that they use. Often, these will result in a quick resolution without having to
progress onto the next stages. If you don’t have the experience (and can’t find someone that does...
recommended) or find that you’re still unable to find the answer, you’ll need to progress to the next steps.