this is a part from /var/log/messages

my question is about the duplicate message .... I am very sure that it is not a duplication IP on the network. what is the problem, why this message?

thank u


Jul 3 16:04:03 gate dhcpd: Dynamic and static leases present for 172.31.5.174.
Jul 3 16:04:03 gate dhcpd: Remove host declaration oslo or remove 172.31.5.174
Jul 3 16:04:03 gate dhcpd: from the dynamic address pool for 172.31.5/24
Jul 3 16:04:03 gate dhcpd: uid lease 172.31.5.174 for client 00:13:d3:38:0b:d7 is duplicate on 172.31.5/24
Jul 3 16:04:03 gate dhcpd: DHCPREQUEST for 172.31.5.174 from 00:13:d3:38:0b:d7 via eth0
Jul 3 16:04:03 gate dhcpd: DHCPACK on 172.31.5.174 to 00:13:d3:38:0b:d7 via eth0
Jul 3 16:05:04 gate dhcpd: DHCPINFORM from 172.31.5.174 via eth0: not authoritative for subnet 172.31.5.0
Jul 3 16:05:07 gate dhcpd: DHCPINFORM from 172.31.5.174 via eth0: not authoritative for subnet 172.31.5.0
Jul 3 16:05:54 gate named[2117]: client 172.31.5.1#34257: RFC 1918 response from Internet for 18.2.31.172.in-addr.arpa
Jul 3 16:09:56 gate dhcpd: DHCPINFORM from 172.31.5.36 via eth0: not authoritative for subnet 172.31.5.0
Jul 3 16:10:00 gate dhcpd: DHCPINFORM from 172.31.5.36 via eth0: not authoritative for subnet 172.31.5.0
Jul 3 16:13:10 gate dhcpd: DHCPREQUEST for 172.31.5.36 from 00:19:d1:2f:56:67 via eth0
Jul 3 16:13:10 gate dhcpd: DHCPACK on 172.31.5.36 to 00:19:d1:2f:56:67 via eth0
Jul 3 16:14:15 gate named[2117]: client 172.31.5.1#34258: RFC 1918 response from Internet for 18.2.31.172.in-addr.arpa
Jul 3 16:15:24 gate named[2117]: client 172.31.5.1#34258: RFC 1918 response from Internet for 131.5.31.172.in-addr.arpa

You don't show us your dhcp.conf file, but I bet you have a statment like "range dynamic-bootp 172.31.a.b-172.31.c.d" and statements like:

host whatever {
hardware ethernet 00:13:d3:38:0b:d7;
fixed-address 172.31.5.174;
}

You can't assign a ip from dynamic range 172.31.a.b-172.31.c.d to a fixed host.
The ip for the host whatever above, must be outside from the dynamic range.

If I guess wrong, please give us your dhcpd.conf file to help us to understand what is going wrong with your setup.

u are the man, mannnn !

u did guess right !

problem solved ... thanks

I found somethigelse in /var/log/message

Jul 4 16:10:22 gate dhcpd: DHCPREQUEST for 172.31.5.139 from 00:0c:29:c2:65:e8 via eth0: unknown lease 172.31.5.139.
Jul 4 16:10:27 gate dhcpd: DHCPREQUEST for 172.31.5.139 from 00:0c:29:c2:65:e8 via eth0: unknown lease 172.31.5.139.
Jul 4 16:10:36 gate dhcpd: DHCPREQUEST for 172.31.5.139 from 00:0c:29:c2:65:e8 via eth0: unknown lease 172.31.5.139.


my dhcp.conf




more /etc/dhcp/dhcpd.conf
allow bootp;
allow booting;

default-lease-time 21600;
max-lease-time 43200;
ddns-update-style ad-hoc;

option routers 172.31.5.1;
option subnet-mask 255.255.255.0;
option domain-name "domain.com";
option domain-name-servers 172.31.5.1;
option netbios-name-servers 172.31.5.2;
option time-offset -5; # Eastern Standard Time
option ntp-servers 172.31.5.1;
authoritative;

subnet 172.31.5.0 netmask 255.255.255.0 {
range dynamic-bootp 172.31.5.180 172.31.5.220;
next-server 172.31.5.10;
filename "pxelinux.0";
}

# Host1
host host1 {
hardware ethernet 00:0C:76:40:8C:1B;
fixed-address 172.31.5.150;
}

............................. the rest of my hosts


# Host30
host host30 {
hardware ethernet 00:191:0A:E5:9C;
fixed-address 172.31.5.30;
}

When a host receives an ip by dhcp, it tries to renew the lease using the same ip. It suggests to dhcp server the "old" ip it was holding.

I think a host was holding the ip 172.31.5.139 (because it received that ip from a dhcp server in the past) and now it is trying to renew it and the server (maybe due to changes in the dynamic range) does not have that ip available anymore as a dynamic ip and it logs this as a warning.

I believe it is not serious.
You can double check this by inspecting the ip the host 00:0c:29:c2:65:e8 received. It must have now an ip from your current dynamic range and this host will not ask for that ip anymore.

u were wright... it is clear now !
thank u