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DHCP question 1

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iSeriesCodePoet

iSeriesCodePoet

Programmer
Jan 11, 2001
1,373
US
I am using (I believe) DHCPD on Slackware 9 and don't really have a problem, but an annoyance.

My Setup:
3 NICs, 2 internal for seperate networks, and 1 extranal. The two internal NICs are assigned IP addresses of 10.1.1.1 and 10.1.2.1. DHCP works on both.

My Problem:
Howerver, whenever I connect up a computer, it will grab an IP address for the other NIC, then Windows will assign a 169. address, then it will grab the proper IP address.

Here is my config:
Code: 
# dhcpd.conf
#
# Configuration file for ISC dhcpd (see 'man dhcpd.conf')
ddns-update-style ad-hoc;
# Upstairs
        option domain-name-servers 10.1.1.1;
subnet 10.1.1.0 netmask 255.255.255.0 {
        ddns-updates off;
        option domain-name-servers 10.1.1.1;
        option domain-name "wills.inet";
        option routers 10.1.1.1;
        range 10.1.1.50 10.1.1.200;
        allow unknown-clients;
        }
# Downstairs
        option domain-name-servers 10.1.2.1;
subnet 10.1.2.0 netmask 255.255.255.0 {
        ddns-updates off;
        option domain-name-servers 10.1.2.1;
        option domain-name "apartment.inet";
        option routers 10.1.2.1;
        range 10.1.2.50 10.1.2.200;
        allow unknown-clients;
        }

Thanks for any help you give,

iSeriesCodePoet
iSeries Programmer/Lawson Software Administrator
[pc2]
See my progress to converting to linux. The Programmer's Knowledge Base ->
 
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Why are you using a class 'C' subnet mask?

Glen A. Johnson
Johnson Computer Consulting
MCP W2K
glen@johnsoncomputers.us


Want to get great answers to your Tek-Tips questions? Have a look at FAQ219-2884
"Action is the proper fruit of knowledge."
Thomas Fuller (1610-1661); English scholar, preacher
 
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What I think the problem really is is that there are two DHCP servers in the same network segment. When your clients boot up, they broadcast for a DHCP server and ask for an address, and which ever one responds the quickest is the one that leases the IP.

What you'll want to do is find a way to segment your network. You could do this with a router or firewall. If you have them, managed switches will allow this as well - VLAN. I would suggest the VLAN, is possible.
 
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Is the annoyance similar to the event in BOLD LETTERS below?

This is a quote from somewhere:)

If no DHCP server is currently available (either because the server is temporarily down or because none exists on the network), the computer selects an IP address from a range of addresses (from 169.254.0.0 - 169.254.255.255) reserved by the Internet Assigned Numbers Authority (IANA) for that purpose. The client uses Address Resolution Protocol (ARP) to ensure that the chosen address is not already being used by another network computer. Once the computer has assigned itself an IP address, it can communicate over TCP/IP with other computers on the LAN that are either configured for APIPA or are manually set to the correct address range and a subnet mask value of 255.255.0.0. APIPA is enabled by default, but can be disabled in some cases. DHCP messages notify the user when they are switched between DHCP addressing and APIPA.

End quote.




 
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This is currently how the network is setup:

Code: 
DSL
   |
   V
IPCop Firewall
   |
   V
Linksys Switching Hub
   |
   V
Linksys Switching Hub
   |
   V
Slackware Firewall
   |              |
   V              V
Dell Laptop    Desktop

Here I am just using crossover cables for testing.


It will be:
Code: 
DSL
   |
   V
Slackware Firewall
   |              |
   V              V
  Hub          Desktop

Here the "upstairs" connection is spread to many systems via a hub and the "downstairs" connection will be a crossover to a single computer.

iSeriesCodePoet
iSeries Programmer/Lawson Software Administrator
[pc2]
See my progress to converting to linux. The Programmer's Knowledge Base ->
 
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I stand corrected primarily because I'm not familiar with slackware but below is the way I see it.

The computer will grab the DCHP offer. It will discover that it doesn't belong to this subnet, so it will release then wait for the other DHCP. But because this correct DHCP will not offer in time then it will take the APIPA address (which starts with 169...) after taking APIPA address it will discover that it doesn't belong to this subnet either so it will release it again and then this slow correct DHCP comes along and offer it's IP address. The PC will grab it, check it and discover that this is where I belong so I will use this :). It seems like the PC belong to a DHCP class and there's a delay occurence configured to the router or anywhere. Even me is a little bit unconviced with this occurence:).
 
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That is exactly what seems to be happening. Any idea on how to fix it?

I can live with it and I am sure my parents can live with it, but my perfectionist side won't.

iSeriesCodePoet
iSeries Programmer/Lawson Software Administrator
[pc2]
See my progress to converting to linux. The Programmer's Knowledge Base ->
 
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What OS's are the client's. I'm just curious about your dns and wins.

Glen A. Johnson
Johnson Computer Consulting
MCP W2K
glen@johnsoncomputers.us


Want to get great answers to your Tek-Tips questions? Have a look at FAQ219-2884
"Action is the proper fruit of knowledge."
Thomas Fuller (1610-1661); English scholar, preacher
 
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Disable APIPA on the clients and see what happens.


Let me know if you need help with the W2K or W98. Good luck.

Glen A. Johnson
Johnson Computer Consulting
MCP W2K
glen@johnsoncomputers.us


Want to get great answers to your Tek-Tips questions? Have a look at FAQ219-2884
"Action is the proper fruit of knowledge."
Thomas Fuller (1610-1661); English scholar, preacher
 
Upvote 0 Downvote
You need a DHCP relay agent in the system. Your DHCP service on the server does not distinguish which interface received the DHCP Request and the wrong side gives out an address. Remove one side of the service and see if it then works correctly.


bob

I know what I know and that's all I know.
 
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