DHCP doesn't assign IP's to client

eash · ‎03-02-2015

Dear All,

I am observing a strange problem in my DHCP setup. There are 6 DHCP pool and 6 Vlan's configured on Cisco 3750 with 128 ip's to lease for each pool. But the DHCP stop leasing ip's after 90 ip's are leased.

When I observe the show ip dhcp bi and show ip dhcp pool are not matching.

Network is 3750==2960==client pc's ( same setup for all the vlan's)

my config is shown,

router#ip dhcp remember
ip dhcp conflict resolution logging

ip dhcp conflict resolution interval 5
ip dhcp excluded-address 192.168.210.1 192.168.210.31
ip dhcp excluded-address 192.168.210.160 192.168.210.254
ip dhcp excluded-address 192.168.211.1 192.168.211.31
ip dhcp excluded-address 192.168.211.160 192.168.211.254
ip dhcp excluded-address 192.168.212.1 192.168.212.31
ip dhcp excluded-address 192.168.212.160 192.168.212.254
ip dhcp excluded-address 192.168.213.1 192.168.213.31
ip dhcp excluded-address 192.168.213.160 192.168.213.254
ip dhcp excluded-address 192.168.214.1 192.168.214.31
ip dhcp excluded-address 192.168.214.160 192.168.214.254
ip dhcp excluded-address 192.168.209.1 192.168.209.31
ip dhcp excluded-address 192.168.209.160 192.168.209.254
!
ip dhcp pool DHCP210
   network 192.168.210.0 255.255.255.0
   default-router 192.168.210.200
   dns-server 172.16.141.13
   lease 2
!
ip dhcp pool DHCP211
   network 192.168.211.0 255.255.255.0
   default-router 192.168.211.200
   dns-server 172.16.141.13
   lease 2
!
ip dhcp pool DHCP212
   network 192.168.212.0 255.255.255.0
   default-router 192.168.212.200
   dns-server 172.16.141.13
   lease 2
!
ip dhcp pool DHCP213
   network 192.168.213.0 255.255.255.0
   default-router 192.168.213.200
   dns-server 172.16.141.13
   domain-name exedy.co.jp
   lease 2
!
ip dhcp pool DHCP214
   network 192.168.214.0 255.255.255.0
   default-router 192.168.214.200
   dns-server 172.16.141.13
   lease 2
!
ip dhcp pool DHCP209
   network 192.168.209.0 255.255.255.0
   default-router 192.168.209.200
   dns-server 172.16.141.13
   lease 2
!

Regards,

Eash

Vasilii Mikhailovskii · ‎03-04-2015

Hello.

Please check ip dhcp conflicts.

PS: it's not a good idea to use L3 switch as DHCP server for 600 clients (waste of CPU).

eash · ‎03-06-2015

Hi Cisco Freak / Vasilii,

Thanks for your reply,

@Cisco Freak,

I am facing problem in VLAN 210 only. I will share the show ip dhcp binding shortly.

@ Vasilii,

Although there are 6 VLAN of 128 IP's each. The users are mainly in the VLAN 210. In the other VLAN there are hardly users.

Eash

sammynom · ‎03-09-2015

Eash,

Is your inter-vlan configured? Please check the attached docs.

eash · ‎03-10-2015

Hi Sammynom,

Inter VLAN is configured. Please let me any specific that I should check. I have configured dhcp as per the config show above. Please find enclosed the outout of sh ip dhcp pool and show ip dhcp bindings. If you see the ip leased in show ip dhcp pool is not matching with show ip dhcp bindings.

@Cisco Freak,

I am facing problem in VLAN 210 only. I will find the capture of show ip dhcp pool and show ip dhcp binding

When we clear ip dhcp bindings * we get the enclosed error.

This problem is really effecting our production. Looking for all your valuable suggestion to resolve this problem.

sammynom · ‎03-10-2015

Hi Each,

Thank you for providing more information. I see that you have 2 pools 210 and 2100.

I also noticed that you excluded addresses: 192.168.210.1- 192.168.210.31/24 and 192.168.210.160-192.168.210.254/24 so your multilayer switch assigns addresses from 192.168.210.32-192.168.210.159/24

I have a couple of questions for you:

1. if 90 users are assigned IP addresses with no problems, what does the 91 user get? does he get an IP, an error?

2. Are you using VRF?

3. what is connected to CAT 3750?

4. How is SVI configured?

5. Do you have vlans?

6. Are you experiencing this problem with all your pools?

eash · ‎03-10-2015

Hi Sammynom,

Thanks for you reply,

Please find my reply below,

1. if 90 users are assigned IP addresses with no problems, what does the 91 user get? does he get an IP, an error?

After 90 or some times 80 IP's are assigned the next client does not any IP from DHCP and the client display only AFIFA IP. I don't see any error in the 3750.

2. Are you using VRF?

No

3. what is connected to CAT 3750?

I have the MPLS router connected to the 3750 for WAN access

I also have the 2960 for each VLAN connected to 3750 for LAN.

4. How is SVI configured?

yes

5. Do you have vlans?

yes

6. Are you experiencing this problem with all your pools?

Right now there are 110 or more uses only VLAN 210 and I am observing this problem in this VLAN.

I have observed one thing if you see the show ip dhcp binding we are see the some weird MAC address against some IP address. It is not the 32 bit. What could be the reason for this.

Request you to consider VLAN 210 and not VLAN 2100.

Eash

sammynom · ‎03-10-2015

Hi Eash,

Thanks for your response. I looked at the binding. An IP address is 32 bits and the mac address is 48 bits. Mac addresses looks normal to me. However, I think I am looking at the output of a 3550 not the 3750. Furthermore, I do not see pool 210! I see the following pools:2100,2110, and 2120.

In addition, Cat 2960 has 24-48 ports how are you accommodating 100+ connections to a single Cat 2960? based on the number of users, I would assume that you have at least 3 switches per Vlan. Regarding the error, it is the output of 3550 not 3750.

if it is possible, please post the output of show run commands of Cat 3750 and Cat 2960. I need to understand your configuration better.

Thanks

eash · ‎03-10-2015

Hi Sammynom,

Thanks for your reply,

The output is of 3750.

I have one 2960 switch per VLAN connecting to 3750. The users are connecting through a wirless access point connected to 2960 switch.

Please find the Cisco of 3750 and 2960 attached.

Request you to please ignore any VLAN 2100 and read it VLAN 210.

Eash

Vasilii Mikhailovskii · ‎03-10-2015

Hello.

Could you share "show ver" from the box having hostname "Router"?

eash · ‎03-11-2015

Hi Vasilii,

Thanks for your reply,

Please find the same.

Eash

Vasilii Mikhailovskii · ‎03-11-2015

Hello.

You might be facing bugs - CSCtl12389 or CSCtz49541.

Try to remove "ip dhcp remember" (and reload the box) command and see if it solves the issue.

eash · ‎03-11-2015

Hi Vasilii,

Thanks for your reply,

I tried you suggestion it didn't work.

Could it be better suggestion to upgrade the IOS? If so request you to kindly suggest a stable version.

Eash

Vasilii Mikhailovskii · ‎03-11-2015

Did you reload the box after command removal?

eash · ‎03-14-2015

Hi Vasilii,

thanks for the reply,

I have upgraded the IOS to c3750e-universalk9-tar.150-2.SE7.tar and disabled ip dhcp remember and reload the box.

Now the number of IP's assigned is gone up to 121. Actually each DHCP pool is configured with 128 IP's. DHCP is not assigning the full quota of IP's configured. It is causing to the customer problem as they has assign reserved IP address to the other users.

One more thing in one DHCP scope 209, although my laptop was connected and I received the first assignable IP address that is 192.168.209.32 but when I checked IP dhcp pool it is not shown.

Eash