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Troubleshoot FOr manual ip binding in DHCP

hI   experts

WE AHVE cISCO 2960 SWITCHES. this switch acts as a dhcp server for the hosts connected to it.

provided mac based binding to the hosts, with enabled dhcp snooping and IP source guard per interface.'

****i have a problem with single host couldnt get an ip from dhcp as he binded based on mac: manualip****

Here is my config:

we have a VLAN99, 70 hosts connected should get an ip based on mac

switch(2960<config>interface vlan99

# ip address 10.10.14.2 255.255.255.0

#ip dhcp snooping

#ip dhcp snooping vlan 99    ********

# ip dhcp excluded-address 10.10.14.3 10.10.14.10

#ip dhcp excluded-address 10.10.14.80 10.10.14.255

Parent pool

#ip dhcp pool prod

#network 10.10.14.0 255.255.255.0            ********

CHILD pool(sample example for single host bind based on mac-id)

#ip dhcp pool amit

#host 10.10.14.31 255.255.255.0

client-identifier 0101.a0b5.55ea.fb    *******

client-name amit

like this i have i have 70 pools for 70 hosts.

#int fa 0/1-48 (all ports are switch ports of vlan with IPsource guard enabled)

#switchport mode access

#switchport access vlan 99

#ip verify source port-security   *********

the above host amit (10.10.14.31 swhould get this ip bindded with mac) but hez not getting manual ip i.e 10.10.14.31, but if an ip excluded from the dhcp free, he can get that ip i.e automatic ip . every other host are getting the ips as binded in the pool manual ip.

checked with

**sh mac-address table dynamic vlan 99   ()

**clear ip dhcp binding *   or  10.10.14.31

** clear ip dhcp snooping binding

*** clear ip dhcp conflict *

tried to change pool names

all these troubleshoot couldnt make me successs in providing amit an manual ip.

can any1 please tell me whats the main root cause of this prob. as every other hosts could get an manual ip except host called amit as above stated

Requesting a quick reply

thanks

& regards

sreekanth

10 REPLIES

Re: Troubleshoot FOr manual ip binding in DHCP

Did you check the mac address? Sometimes for some weird reason, the mac address labeled on the NIC or due to NIC changes, you could be using an incorrect mac.

How to check if you are using the correct mac? (The one the DHCP gets)

Just get your host to take a normal Pool address, with no mac binding, a dynamic address, then go to the switch and use the command "show ip dhcp binding", look for the dynamic configured address and You will have the CORRECT mac address there

Then use THAT one as the client identifier

(You will have to clear ip dhcp binding x.x.x.x <- the dynamic ip, or you should get a binding error)

Purple

Troubleshoot FOr manual ip binding in DHCP

Hi,

client-identifier 0101.a0b5.55ea.fb  this can't be a valid source MAC address as the I/G is set to 1 which means it is a group address which can only be used as destination.

Regards.

Alain

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New Member

Re: Troubleshoot FOr manual ip binding in DHCP

HI all

please give few mins in going through the attached file.

the mac address i have provided above  is not the correct one.

here is the modifications i have done in assigning ips to hosts. and provided u all the possible outputs in attached file.

10.10.14.39         0110.78d2.c392.df    this is amits mac id..manual binding

10.10.14.93         1078.d2c3.92df          Apr 13 1993 11:14 PM    Automatic  getting automatic ip

if i dint left any ip freee ..amit couldnt get ip from dhcp pool.as so hez not in the network.

can you please look in to the outputs and guide me what should be done.

#sh run

#sh ip dhcp binding

#sh ip dhcp snooping binding

thganks & regards

srikanth

Purple

Troubleshoot FOr manual ip binding in DHCP

Hi,

Clear this binding and then change your manual binding like this:

ip dhcp pool amit

host 10.10.14.31 255.255.255.0

hardware-address  01a0.b555.eafb   

client-name amit

Regards.

Alain

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New Member

Troubleshoot FOr manual ip binding in DHCP

Hi cadet

whats the difference in using betweeen client-identifier and hardware-adress for child pool..

note: to add on this ,amit is the only one using linux OS. wherein all others are using windows machine does  this may be concern  we need to think about. 

Thanks &  regards

srikanth

Purple

Troubleshoot FOr manual ip binding in DHCP

Hi,

As you see in the output of sh ip dhcp bindings , the client is using its hardware address  as client-identifier as all Linux do.

So do the change I suggested and your client will get its IP address.

Don't forget to rate posts if helpful.

Regards.

Alain

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New Member

Re: Troubleshoot FOr manual ip binding in DHCP

HI alain

still the same problem persist..

still he got the ip 10.10.14.93 where in he should get 10.10.14.39 (assigned new 1)..

even i saw. the port learned mac-address and its the same mac id which has taken automatic binding.

10.10.14.93         1078.d2c3.92df          Apr 14 1993 03:47 AM    Automatic

is there any thing  sh command i should provide u.

Thanks & regards

srikanth

Purple

Re: Troubleshoot FOr manual ip binding in DHCP

Hi,

ip dhcp pool amit

   host 10.10.14.39 255.255.255.0

   hardware-address 0110.78d2.c392.df  --->this is not a valid MAC address

   client-name amit

10.10.14.93         1078.d2c3.92df          Apr 14 1993 03:47 AM    Automatic

You didn't clear the binding ? 

1078.d2c3.92df   is the correct hardware-address

clear all the  bindings   and  put the correct MAC address

Don't forget to rate if helpful

Regards.

Alain

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New Member

Re: Troubleshoot FOr manual ip binding in DHCP

Hi cadet yes made a mistake in giving correct mac-id...but issue isnt resolved at. will re check the issue. and

rated as you see each and every point  in depth in analysing it and explain us where we are doing mistake

here is the mac id

  1078.d2c3.92df

thanks for your help

will update in short while whether hez getting desired IP. it takes few mins.

regards

srikanth

Purple

Troubleshoot FOr manual ip binding in DHCP

Hi,

what you must do is

1) clear the bindings for this MAC address

2) do a dynamic binding to get sure it is using MAC address as client-id

3) reclear the binding fo this client

4) put the correct syntax hardware-address xxxx.xxxx.xxxx

5) renew the lease on the client

Let us know

Regards.

Alain.

Don't forget to rate helpful posts.
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