weird stuff with netork

[zeek333]

Hi
I'm using BT(not at me but looks like BT2700HGV) router, few win2003 servers and few Ubuntu 8.04 servers 2 eth in each server, problem is with one of ubuntu server its changes IP's by it self.
Servers are on DHCP client and BT router is setup as DHCP server, and its recognise all server host names and IPs. This BT router also let me set this particular server IP as fixed IP, but it doesn't work with only one server when I set these IP's after moment its changes IP to something else. eg
after insall i set in router IPs eth0 192.168.1.100 and eth1 10.10.10.1 (ext IP) but after few moments when i checked router its didnt recognise one of eth. after network restart its assign new IPs eth0 10.0.0.2 and eth1 10.0.0.3

New devices added to BT should should assign internal IP 192.168.1.X but that server both eth changes to ext IP

Server is fresh ilstalled version.

[riddler]

When one does an ipconfig what DNS suffix, IP address and Default Gateway does it obtain?

BT's router give out gateway.2wire.net as the DNS suffix.

If one sees above DNS suffix the 2700 has an issue. if the dns suffix says something different you will very possibly have a rogue DHCP server on the network so lets start there, what is the DNS suffix?

[sej7278]

Why are you using DHCP on servers, what's wrong with just setting up fixed IP's, then you don't have to fight the BT router or NetworkManager.

[riddler]

One should use DHCP so that DNS management works more efficiently. One would turn off DHCP on the BT router and have 1 server only handing out DHCP. This helps that server resolve DNS queries much more efficiently since IT leased the IP addresses to the clients.

[sej7278]

dhcp has little or nothing to do with dns.

you should switch off dhcp and go to static ip's that will instantly solve the problem.

[riddler]

I am afraid you are mistaken sej.

DHCP does have something to do with DNS.

When a client sends a DHCP request and a server acknowledges and sends DHCP info such is IP, DG, WINS server and DNS server the server will register the clients details in DNS aswell with updated information.

Although you can technically speaking just specify all the IP addresses on a network, in order to keep up to date records of said network and to guarantee network name resolution the domain controller should dish out addresses so that as i stated they can quickly resolve DNS.

Specifying the IP addresses may work as first however there may be varying side effects such as client name resolution failing or even worse from a technical support standpoint, if the network adapter or network cable were to malfunction troubleshooting the issue will not be as obvious since the client will still have an IP address. If said client were to have obtained an IP via DHCP it would obtain the tell-tale 169 APIPA address.

Back when I had an onsite IT chap our network had 24 clients on it of which 2 had a specified IP address. Those clients had a multitude of DNS name resolution issues of which were resolved instantly by switching those clients to DHCP.

[alastair]

im gonna have to side with riddler on this one.

dns is important on the network, you can specify the ip addresses but thats just sloppy.

dns name resolution is one potential issue with specifying ip addresses, another is long log on times to the domain and yet another is as riddler said static addresses make troubleshooting more difficult. only a tiny bit but if you dont know what you are doing it may confuse matters

[p373mcc]

The advantage of using DHCP is that changes to the network, for example a change in the address of the DNS server, need only be changed at the DHCP server, and all network hosts will be reconfigured the next time their DHCP clients poll the DHCP server. As an added advantage, it is also easier to integrate new computers into the network, as there is no need to check for the availability of an IP address. Conflicts in IP address allocation are also reduced.

A DHCP server can provide configuration settings using two methods:

MAC Address

This method entails using DHCP to identify the unique hardware address of each network card connected to the network and then continually supplying a constant configuration each time the DHCP client makes a request to the DHCP server using that network device.

Address Pool

This method entails defining a pool (sometimes also called a range or scope) of IP addresses from which DHCP clients are supplied their configuration properties dynamically and on a fist come first serve basis. When a DHCP client is no longer on the network for a specified period, the configuration is expired and released back to the address pool for use by other DHCP Clients.