DHCP Server not sending offers!

Fri Jul 18 10:08:06 UTC 2014

Greetings Eugène,

is the dhcp server within the same ip subnet like the clients ? What 
does the dhcp server log file tell you about the missing offers ?

Best regards,
Daniel

Am 18.07.2014 11:30, schrieb Eugène Ngontang:
> Hi have got an issue with my DHCP server that I can not locate the 
> origin.
>
> In fact I have a group of linux hosts with a dhcp server on which I 
> made a reservation, configured to assign IP addresses to hosts 
> staticaly (fixed address), with lease time of 6 hours.
>
> The problem is that at least one time per day, all hosts stop getting 
> addresses from the server, while the dhcpd daemon is still running.
>
> I have check, and noticed that the hosts do not longer receive 
> DHCPOFFERs from the server, when they send a DHCHPDISCOVER.
>
> With tcpdump on the server I can see request from clients, and the 
> server just ignores them. I've try cleaning the dchpd leases file, but 
> it doesn't fix the issue, but when I restart the service, all things 
> turn fine.
>
> What I would like to, is know what can the server be doing at this 
> special time when a client want its IP address to be released? I've 
> searched in several forums, and nobody seems to be able to answer me, 
> since it seems to be a programming issue.
>
> How can I get a technical documentation of dhcpd? Is it possible to 
> understand when and why a server can ignore DHCPREQUEST?
>
> Do someone here has already got this issue?
>
> What I've done temporarely, is to set a crontab to restart the dhc 
> service each day at 6:03, 12:03, and 18:03.
>
> Here is an  extract of tcpdump on the server :
>
> *tcpdump: listening on eth0, link-type EN10MB (Ethernet), capture size 
> 1500 bytes*
> *2014-05-04 12:56:07.419712 00:01:80:7d:db:14 > Broadcast, ethertype 
> IPv4 (0x0800), length 346: (tos 0x0, ttl 128, id 0, offse*
> *t 0, flags [none], proto: UDP (17), length: 328) 0.0.0.0.bootpc > 
> 255.255.255.255.bootps: [udp sum ok] BOOTP/DHCP, Request fr*
> *om 00:01:80:7d:db:14, length: 300, xid:0xc768345, secs:3, flags: 
> [none] (0x0000)*
> *          Client Ethernet Address: 00:01:80:7d:db:14*
> *          Vendor-rfc1048:*
> *            DHCP:DISCOVER*
> *            RQ:10.242.40.18*
> *            HN:"FR-LYS-LX004"*
> *PR:SM+BR+TZ+T121+DN+NS+HN+YD+YS+NTP+MTU+T119+DG*
> *        0x0000:  4500 0148 0000 0000 8011 39a6 0000 0000*
> *        0x0010:  ffff ffff 0044 0043 0134 f634 0101 0600*
> *        0x0020:  0c76 8345 0003 0000 0000 0000 0000 0000*
> *        0x0030:  0000 0000 0000 0000 0001 807d db14 0000*
> *        0x0040:  0000 0000 0000 0000 0000 0000 0000 0000*
> *        0x0050:  0000 0000 0000 0000 0000 0000 0000 0000*
> *        0x0060:  0000 0000 0000 0000 0000 0000 0000 0000*
> *        0x0070:  0000 0000 0000 0000 0000 0000 0000 0000*
> *        0x0080:  0000 0000 0000 0000 0000 0000 0000 0000*
> *        0x0090:  0000 0000 0000 0000 0000 0000 0000 0000*
> *        0x00a0:  0000 0000 0000 0000 0000 0000 0000 0000*
> *        0x00b0:  0000 0000 0000 0000 0000 0000 0000 0000*
> *        0x00c0:  0000 0000 0000 0000 0000 0000 0000 0000*
> *        0x00d0:  0000 0000 0000 0000 0000 0000 0000 0000*
> *        0x00e0:  0000 0000 0000 0000 0000 0000 0000 0000*
> *        0x00f0:  0000 0000 0000 0000 0000 0000 0000 0000*
> *        0x0100:  0000 0000 0000 0000 6382 5363 3501 0132*
> *        0x0110:  040a f228 120c 0c46 522d 4c59 532d 4c58*
> *        0x0120:  3030 3437 0d01 1c02 790f 060c 2829 2a1a*
> *        0x0130:  7703 ff00 0000 0000 0000 0000 0000 0000*
> *        0x0140:  0000 0000 0000 0000 9c57 4f09*
>
> I have pasted here above the dump just for one host, the rest is the 
> same and only the MAC address differs.
>
> Below is an extract of a client system log file :
>
> * Apr 30 03:04:47 00-01-80-7e-38-fd dhclient[653]: DHCPDISCOVER on eth0*
> *to 255.255.255.255 port 67 interval 6 (xid=0x1e903fe)*
> *Apr 30 03:04:53 00-01-80-7e-38-fd dhclient[653]: DHCPDISCOVER on eth0*
> *to 255.255.255.255 port 67 interval 8 (xid=0x1e903fe)*
> *Apr 30 03:05:01 00-01-80-7e-38-fd dhclient[653]: DHCPDISCOVER on eth0*
> *to 255.255.255.255 port 67 interval 10 (xid=0x1e903fe)*
> *Apr 30 03:05:11 00-01-80-7e-38-fd dhclient[653]: DHCPDISCOVER on eth0*
> *to 255.255.255.255 port 67 interval 16 (xid=0x1e903fe)*
> *Apr 30 03:05:27 00-01-80-7e-38-fd dhclient[653]: DHCPDISCOVER on eth0*
> *to 255.255.255.255 port 67 interval 18 (xid=0x1e903fe)*
> *Apr 30 03:05:45 00-01-80-7e-38-fd dhclient[653]: DHCPDISCOVER on eth0*
> *to 255.255.255.255 port 67 interval 3 (xid=0x1e903fe)*
> *Apr 30 03:05:48 00-01-80-7e-38-fd dhclient[653]: No DHCPOFFERS received.*
> *Apr 30 03:05:48 00-01-80-7e-38-fd dhclient[653]: No working leases in*
> *persistent database - sleeping.*
>
>
> Please can you help to idendify where the problem comes from?
>
> I thank you so much for your attention.
>
> Best regards,
> Eugène NG
> -- 
> ngonta_e at epitech.net <mailto:ngonta_e at epitech.net>
> sympavali at gmail.com <mailto:sympavali at gmail.com>
> ------------------------------------------------------------
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>
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