DHCP Issues

alabedekenny · ‎03-06-2014

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.

srprasaad_nj · ‎03-06-2014

Hi Alabedekenny,

Please can you try upgarding or downgrading the IOS .

alabedekenny · ‎03-07-2014

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

Jeff Van Houten · ‎03-06-2014

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

alabedekenny · ‎03-07-2014

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.