DHCP server assigns same ip address to multiple clients

[lasha7701]

we have a trouble with dhcp server in our network. we have cisco c3850 L3 switch as a dhcp server and the problem is that, sometimes clients can not receive lease.
when I type  #show ip dhcp binding, 

192.168.137.16  0100.21b7.5e81.64       Sep 21 2015 03:37 PM    Automatic  Active     Vlan137
192.168.166.24  0100.e045.8600.2c       Sep 20 2015 11:58 PM    Automatic  Active     Vlan166
192.168.179.22  0160.a44c.548a.76       Sep 21 2015 02:12 PM    Automatic  Active     Vlan179
192.168.179.22  0100.19db.87d0.5c       Sep 21 2015 09:15 AM    Automatic  Active     Vlan179
192.168.190.55  0100.2522.e1b8.7a       Sep 20 2015 10:00 PM    Automatic  Active     Vlan40
192.168.190.93  0100.1e8c.9fb7.f7       Sep 20 2015 11:02 PM    Automatic  Active     Vlan40
192.168.190.96  0100.0ffe.85ea.54       Sep 20 2015 08:36 PM    Automatic  Active     Vlan40
192.168.190.10  0148.5b39.c39c.86       Sep 20 2015 11:58 PM    Automatic  Active     Vlan40
192.168.190.10  0100.0ffe.69a8.59       Sep 20 2015 11:47 PM    Automatic  Active     Vlan40
192.168.190.12  01e0.3f49.12fb.84       Sep 20 2015 10:45 PM    Automatic  Active     Vlan40
192.168.190.20  0100.19db.87c8.53       Sep 20 2015 07:50 PM    Automatic  Active     Vlan40
192.168.190.20  01bc.5ff4.e2f4.c3       Sep 20 2015 10:16 PM    Automatic  Active     Vlan40
192.168.190.21  0134.aa8b.8a55.72       Sep 20 2015 10:22 PM    Automatic  Active     Vlan40

I see that the DHCP server assigns same ip address to multiple clients, even though there is free addresses to lease. what could be the reason, how to correct it? thanks

P.S. sorry bad english

[John Blakley]

I believe, by default, Cisco pings the address twice before assigning it to another computer. This could be an ios bug... Can you post the config of one of your pools? For example, vlan 40?

HTH,

John

[lasha7701]

!
ip dhcp pool accounting_new
 network 192.168.190.0 255.255.255.0
 default-router 192.168.190.1
 dns-server 192.168.0.1 192.168.1.3
 lease 0 8
!

Anyway, As I know, router shuld not write same ip address in binding table.

thanks for reply

[John Blakley]

I might suggest a tac case to see if they can point you to a potential bug in the ios....

HTH,

John