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DNS Issues

Tez

DNS Issues
« on: August 11, 2002, 09:57:35 PM »
Could someone explain a little about DNS when using e-smith 4.1?

I have had e-smith running now for a little over a year, I don't know anything about Linux and the only configuration I do is via the console. e-smith is the server gateway to a small network (6 machines).

On the network I also have Win2k Server running Active Directory. The Win2k server acts as a domain controller  'mynetwork.local' and in the network properties of the Win2k server and the Win2k workstations I have set it up like this,
Use the following IP address 192.168.1.10x
Subnet mask 255.255.255.0
Default gateway 192.168.1.100 (e-smith)
Use the following DNS server 192.168.1.100 (e-smith) I would like to have the IP address of the DNS server the same as the Win2k server and not the e-smith server, is this possible? If I unassign the DNS on the workstations or if I use any other IP other than that of e-smith I can't connect to the Internet?

This is the e-smith configuration

Use DHCP (send ethernet address as client identifier)
Dynamic DNS service 'Off'
DHCP 'Off' to local network
Select master DNS server address 'Blank'

When I look at the configuration via the browser console the DNS is the same as the IP address, but I can't change this to the Win2k server IP address?

I have named the Workgroup that e-smith belongs to as the same as the Domain that Win2k runs to make it easier, 'mynetwork'



Has anyone setup e-smith as a server/gateway using a Win2k server for interal services like roaming profiles/file sharing etc and would you be able to give some advice and configurations?

Thanks in advance.

Tez

Jeff Pancrazio

Re: DNS Issues
« Reply #1 on: August 19, 2002, 06:16:34 AM »
Remove all the CAPS to reply. I think what u need to do is have windows 2000 either be the secondary DNS server, which isnt great since it is also hosting AD, maybe a better solution would be to use the

Using forwarders
DNS servers can be configured to send all recursive queries to a selected list of servers, known as forwarders. Servers used in the list of forwarders provide recursive lookup for any queries that a DNS server receives that it cannot answer based on its local zones. During the forwarding process, a DNS server configured to use forwarders (either one or more servers, based upon the forwarders list) essentially behaves as a DNS client to its forwarders.

Benefits of using forwarders
Forwarders are often desirable when access to remote DNS servers requires use of a slow link, such as a fast-speed internal network linked to the Internet over a relatively low-speed connection. Using forwarders in this situation can cut down on expensive traffic over the low-speed link in two ways:

Reduce the number of overall queries that get sent across the slow link — for example, if your DNS server has a slow, expensive dial-up connection to an Internet service provider (ISP).
When the DNS server used as a forwarder for your internal network receives a query for a remote name on the Internet, it can directly contact remote servers on the Internet. It can repeat additional queries until it determines the authoritative server for the name. Once it finds the authoritative server, the forwarder contacts it and receives a complete response.

Another option that can reduce traffic is using a DNS server on the Internet as a forwarder. Before deciding on this configuration, obtain permission to use an Internet DNS server as your designated forwarder, such as a server managed by your ISP. In this configuration, the DNS server at your ISP is forwarded all remote queries once and responds only when it has the complete answer. Each query represents a single round-trip across the slow link.

Share remote results on your local network.
Forwarders provide a way to share information about remote names with a group of DNS servers located in the same area. For example, assume your organization has several DNS servers on a LAN. Rather than having each server send queries through a firewall and out to the Internet, all DNS servers are configured to forward queries to one DNS server (perhaps sitting on the firewall) that makes the necessary queries to the remote servers. In the process, the forwarder builds up a cache of Internet DNS names from the responses it receives. Over time, as local DNS servers continue to forward queries to it, the forwarder answers more queries from its cache because it begins to have an increasing number of answers based on previous queries for the same or similar names.

As shown in the following graphic, a forwarder is typically used in a barrier or firewall that exists between your network and the Internet. However, this is just one suggested configuration and not a requirement for using forwarders.

 
Enlarge figure
 
When a list of forwarders is configured, listed servers are identified by IP address. The first server listed should be preferred and used primarily to build a local cache. Generally speaking, however, more than one forwarder should be listed. Each server on the list is only tried once and any additional retry attempts to the same server can only be caused by repeating its IP address in the list.

If a DNS server is not configured to use forwarders, it uses the normal iterative query process to answer recursive queries for remote names.

Using forwarders exclusively (no recursion)
When a DNS server is configured to use forwarders, they are used before any other means of resolving a name is tried. If the list of forwarders fails to provide a positive answer, a DNS server can attempt to resolve the query itself using iterative queries and standard recursion.

A server can also be configured to not perform recursion after forwarders fail. In this configuration, the server does not attempt any further recursive queries itself to resolve the name. Instead, it fails the query if it does not get a successful query response from any of the forwarders.

This forces a DNS server to use its configured forwarders exclusively to perform final resolution when resolving a name query. In this mode of operation, a server configured to use forwarders can still check in its configured zones first to attempt to resolve a queried name. If it finds a match in its authoritative data there, it can answer the query based on that information.

To use this option, select the Do not use recursion option on the Forwarders tab when a server is configured to use forwarders.

 Note

When using forwarders, queries are sent to each forwarder in the list, which is given a time-out value, in seconds, within which it must respond before the next forwarder is tried.

phil

Re: DNS Issues
« Reply #2 on: August 29, 2002, 12:14:24 PM »
Tez - i have exactly what you are trying to do already working at home, although i am using a full domain rather than a workgroup the essentials should apply.
Basically the set up is as follows.
esmith is setup as gateway/firewall and all external DNS queries are handled by it.
w2k server has DNS server enabled with NO root domain (delete the "." entry) and forwarding turned on. The forwarding is pointed to the esmith box.

All workstations DHCP from the w2k machine with the WS DNS server set to the w2k box, this allows AD and ad/dns to work correctly and still resolves all external queries.

Sorry i haven't got a full step by step as i set this up a while ago and it's not that fresh in the mind.

Duncan Drury

Re: DNS Issues
« Reply #3 on: November 27, 2003, 12:53:41 PM »
Could anyone tell me how to configure forwarders for SME Servers DNS?