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DHCP Issues

Hello All,

I need some urgent assistance with some DHCP Issues in my network.

Recently we noticed users having problems getting IP addresses from IOS DHCP Server.

Please see my configs below:

3750X STACK (IOS Version 12.2(58r)SE, RELEASE SOFTWARE (fc1))

ip dhcp excluded-address 172.20.55.1 172.20.55.20

ip dhcp excluded-address 172.20.55.240 172.20.55.254

ip dhcp pool VLAN55

   network 172.20.55.0 255.255.255.0

   default-router 172.20.55.254

   dns-server 172.20.180.9 172.20.180.10

   option 43 ascii 172.20.35.2

There are two 2960s (access layer switches) connecting to the 3750.

In this vlan, both LAN and wireless users are not more than 30, but the switch issues out all available IP addresses within five hours or so, hence it cant respond with an IP address for any new DHCP request. Hence, users are not able to get IP address until we clear the DHCP binding and sometimes restart DHCP service on the switch.

This issues is really disturbing me. I have enabled DHCP snooping on the 3750 but the problem persists. I'm having similar issue with another 3560 switch, with similar configuration and also connecting to two 2960 access layer switches.

Yet I have tens of other 3650s as dhcp servers in other vlans with no problem.

Here pasted below is the output from the 3750 just few hours after clearing the dhcp binding and restarting the dhcp service:

FMN_GPP_3750_STACK_IT_RM#sh ip dhcp bin

Bindings from all pools not associated with VRF:

IP address          Client-ID/              Lease expiration        Type

                    Hardware address/

                    User name

172.20.35.135       0108.2e5f.239a.cf       Mar 07 2014 06:45 AM    Automatic

172.20.35.172       018c.0c90.3f78.be       Mar 06 2014 08:53 AM    Automatic

172.20.55.54        8c77.1678.3e86          Mar 07 2014 06:38 AM    Automatic

172.20.55.62        30aa.bd3b.029d          Mar 07 2014 08:52 AM    Automatic

172.20.55.64        01a0.edcd.80ef.d5       Mar 07 2014 06:38 AM    Automatic

172.20.55.65        01cc.55ad.cd82.9e       Mar 07 2014 08:51 AM    Automatic

172.20.55.69        01a0.6cec.1b70.64       Mar 07 2014 08:52 AM    Automatic

172.20.55.70        30aa.bd3e.29b3          Mar 07 2014 06:41 AM    Automatic

172.20.55.72        8c77.1648.db78          Mar 07 2014 06:49 AM    Automatic

172.20.55.77        8c77.1635.3a27          Mar 07 2014 08:05 AM    Automatic

172.20.55.78        01f0.7d68.6bff.15       Mar 07 2014 06:46 AM    Automatic

172.20.55.79        0100.2376.0783.3e       Mar 07 2014 07:27 AM    Automatic

172.20.55.80        30aa.bd3b.257e          Mar 07 2014 08:51 AM    Automatic

172.20.55.81        01c4.88e5.467c.33       Mar 07 2014 06:46 AM    Automatic

172.20.55.83        30aa.bd08.38de          Mar 07 2014 07:35 AM    Automatic

172.20.55.84        0073.8d34.c343          Mar 07 2014 06:48 AM    Automatic

172.20.55.85        0118.8796.f57e.d9       Mar 07 2014 07:25 AM    Automatic

172.20.55.86        0160.21c0.8a3f.97       Mar 07 2014 06:49 AM    Automatic

172.20.55.87        8c71.f8ea.c12c          Mar 07 2014 06:50 AM    Automatic

172.20.55.88        0170.aab2.743b.d1       Mar 07 2014 08:50 AM    Automatic

172.20.55.91        8c77.1636.0412          Mar 07 2014 06:55 AM    Automatic

172.20.55.92        0100.237d.200b.f0       Mar 07 2014 06:53 AM    Automatic

172.20.55.94        016c.f373.c74d.a1       Mar 07 2014 06:54 AM    Automatic

172.20.55.95        000c.e700.eb45          Mar 07 2014 06:59 AM    Automatic

172.20.55.96        0100.80f0.db66.52       Mar 07 2014 06:59 AM    Automatic

172.20.55.97        0140.5fbe.2057.aa       Mar 07 2014 07:07 AM    Automatic

172.20.55.98        018c.0c90.3351.d0       Mar 07 2014 07:01 AM    Automatic

172.20.55.101       018c.0c90.3352.40       Mar 07 2014 07:01 AM    Automatic

172.20.55.102       018c.0c90.3352.50       Mar 07 2014 07:01 AM    Automatic

172.20.55.103       0154.3d37.1d58.c0       Mar 07 2014 07:01 AM    Automatic

172.20.55.105       018c.0c90.3616.00       Mar 07 2014 07:01 AM    Automatic

172.20.55.108       018c.0c90.3359.00       Mar 07 2014 07:03 AM    Automatic

172.20.55.109       0184.3a4b.3dc2.e0       Mar 07 2014 07:03 AM    Automatic

172.20.55.110       017c.6193.351b.32       Mar 07 2014 07:03 AM    Automatic

172.20.55.120       30aa.bd10.998e          Mar 07 2014 07:08 AM    Automatic

172.20.55.121       30aa.bd5a.221c          Mar 07 2014 07:12 AM    Automatic

172.20.55.122       0104.f7e4.2e5a.71       Mar 07 2014 07:10 AM    Automatic

172.20.55.123       98d6.f792.e1cd          Mar 07 2014 08:26 AM    Automatic

172.20.55.124       30aa.bd37.4d3d          Mar 07 2014 08:33 AM    Automatic

172.20.55.125       8c77.1648.51e8          Mar 07 2014 07:15 AM    Automatic

172.20.55.126       8c77.1624.c9d7          Mar 07 2014 07:12 AM    Automatic

172.20.55.127       018c.0c90.3358.f0       Mar 07 2014 07:17 AM    Automatic

172.20.55.128       30aa.bd5b.8d16          Mar 07 2014 07:27 AM    Automatic

172.20.55.129       1008.c101.4b18          Mar 07 2014 08:48 AM    Automatic

172.20.55.130       018c.0c90.3615.f0       Mar 07 2014 07:17 AM    Automatic

172.20.55.131       0100.e3b2.1165.4c       Mar 07 2014 07:18 AM    Automatic

172.20.55.132       0164.b310.b279.98       Mar 07 2014 07:21 AM    Automatic

172.20.55.133       406f.2ad1.84ab          Mar 07 2014 07:22 AM    Automatic

172.20.55.135       01c4.62ea.1684.61       Mar 07 2014 07:24 AM    Automatic

172.20.55.136       30aa.bd30.4c8d          Mar 07 2014 07:33 AM    Automatic

172.20.55.137       01cc.08e0.c14f.77       Mar 07 2014 07:25 AM    Automatic

172.20.55.140       0130.694b.c3c8.33       Mar 07 2014 07:26 AM    Automatic

172.20.55.144       f01c.1311.e623          Mar 07 2014 07:55 AM    Automatic

172.20.55.145       0118.3451.672f.8e       Mar 07 2014 07:40 AM    Automatic

172.20.55.146       0150.ccf8.e491.5d       Mar 07 2014 07:31 AM    Automatic

172.20.55.147       30aa.bd1c.31f4          Mar 07 2014 07:32 AM    Automatic

172.20.55.158       30aa.bd25.21fa          Mar 07 2014 07:34 AM    Automatic

172.20.55.159       8c77.1644.991f          Mar 07 2014 08:06 AM    Automatic

172.20.55.160       30aa.bd22.aa26          Mar 07 2014 07:36 AM    Automatic

172.20.55.163       8c77.1690.d9d7          Mar 07 2014 07:39 AM    Automatic

172.20.55.164       406f.2ae9.8d90          Mar 07 2014 07:35 AM    Automatic

172.20.55.167       0140.f308.9649.b6       Mar 07 2014 07:36 AM    Automatic

172.20.55.169       0140.5fbe.ab77.f7       Mar 07 2014 07:38 AM    Automatic

172.20.55.170       30aa.bd1c.1f55          Mar 07 2014 07:40 AM    Automatic

172.20.55.171       0124.f5aa.6d9f.77       Mar 07 2014 07:40 AM    Automatic

172.20.55.172       30aa.bd30.5922          Mar 07 2014 08:13 AM    Automatic

172.20.55.173       8c77.1622.5b49          Mar 07 2014 07:50 AM    Automatic

172.20.55.175       011c.b094.9139.a4       Mar 07 2014 07:46 AM    Automatic

172.20.55.176       0170.aab2.0e62.a2       Mar 07 2014 07:49 AM    Automatic

172.20.55.177       01ac.fdec.6fdd.c5       Mar 07 2014 07:49 AM    Automatic

172.20.55.178       4491.db8a.34d3          Mar 07 2014 07:53 AM    Automatic

172.20.55.179       01ac.f1df.0a01.0d       Mar 07 2014 07:52 AM    Automatic

172.20.55.181       01e0.c97a.ded0.0c       Mar 07 2014 07:52 AM    Automatic

172.20.55.183       0184.8e0c.628a.95       Mar 07 2014 07:54 AM    Automatic

172.20.55.186       0130.7c30.ab0a.f6       Mar 07 2014 07:57 AM    Automatic

172.20.55.188       01f4.0b93.e40f.af       Mar 07 2014 07:57 AM    Automatic

172.20.55.189       30aa.bd23.6fcb          Mar 07 2014 08:06 AM    Automatic

172.20.55.190       30aa.bd1c.4f17          Mar 07 2014 08:12 AM    Automatic

172.20.55.191       8c77.1604.5b13          Mar 07 2014 08:06 AM    Automatic

172.20.55.192       30aa.bd37.432d          Mar 07 2014 08:10 AM    Automatic

172.20.55.194       8c77.1678.8b0a          Mar 07 2014 08:13 AM    Automatic

172.20.55.195       0168.9423.9177.2d       Mar 07 2014 08:52 AM    Automatic

172.20.55.196       30aa.bd00.115c          Mar 07 2014 08:21 AM    Automatic

172.20.55.198       01b0.df3a.899e.b1       Mar 07 2014 08:10 AM    Automatic

172.20.55.199       0120.107a.116b.cf       Mar 07 2014 08:12 AM    Automatic

172.20.55.200       01a4.1731.230d.8c       Mar 07 2014 08:12 AM    Automatic

172.20.55.201       0128.e02c.9948.13       Mar 07 2014 08:17 AM    Automatic

172.20.55.202       8c77.1636.54da          Mar 07 2014 08:25 AM    Automatic

172.20.55.206       b8b4.2eb8.f884          Mar 07 2014 08:21 AM    Automatic

172.20.55.211       0118.8796.865a.32       Mar 07 2014 08:24 AM    Automatic

172.20.55.216       b8b4.2eee.d621          Mar 07 2014 08:30 AM    Automatic

172.20.55.217       8c77.1649.4b85          Mar 07 2014 08:27 AM    Automatic

172.20.55.222       8c77.1677.2999          Mar 07 2014 08:34 AM    Automatic

172.20.55.223       8c77.1636.7ea7          Mar 07 2014 08:35 AM    Automatic

172.20.55.224       0194.d771.22fd.bf       Mar 07 2014 08:28 AM    Automatic

172.20.55.225       28fb.d39d.e2b7          Mar 07 2014 08:48 AM    Automatic

172.20.55.226       30aa.bd11.4d0a          Mar 07 2014 08:30 AM    Automatic

172.20.55.227       0138.aa3c.91fd.e8       Mar 07 2014 08:32 AM    Automatic

172.20.55.228       0108.1196.98f0.84       Mar 07 2014 08:40 AM    Automatic

172.20.55.229       01e0.a670.f47e.95       Mar 07 2014 08:35 AM    Automatic

172.20.55.231       8c77.1624.fe31          Mar 07 2014 08:41 AM    Automatic

172.20.55.232       014c.3c16.2e45.63       Mar 07 2014 08:51 AM    Automatic

172.20.55.233       0188.329b.8c55.86       Mar 07 2014 08:41 AM    Automatic

172.20.55.235       0023.b1ce.4f35          Mar 07 2014 08:46 AM    Automatic

172.20.55.238       a816.b263.33df          Mar 07 2014 08:49 AM    Automatic

172.20.55.239       30aa.bd25.1967          Mar 07 2014 08:48 AM    Automatic

FMN_GPP_3750_STACK_IT_RM#

Where is the switch getting that number of dhcp request when only about 30 users are in the vlan?

I even enabled dhcp snooping but the problem persists. Now I have to clear dhcp binding and restart dhcp service almost every four hours.

Can you please help me here?

Thank you.

4 REPLIES
New Member

DHCP Issues

Hi Alabedekenny,

Please can you try upgarding or downgrading the IOS .

New Member

DHCP Issues

sita rama prasad wrote:

Hi Alabedekenny,

Please can you try upgarding or downgrading the IOS .

I dont think it is the IOS because I have several other switches with the same IOS, and not giving problem.

Thanks

Re: DHCP Issues

Just glancing it looks like no mac addresses are repeated. And you have wireless. Where is this located? Any chance random passers by can attach to your ssid?

Sent from Cisco Technical Support iPad App

New Member

DHCP Issues

Jeff Van Houten wrote:

Just glancing it looks like no mac addresses are repeated. And you have wireless. Where is this located? Any chance random passers by can attach to your ssid?

Sent from Cisco Technical Support iPad App

Yes I have wireless, but it is very secured.

I'm sure there's no chance that random passers by can connect to the network.

It's a very strance thing I still do not understand how to solve.

Thanks for your help.

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