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DHCP & port connection problem

Hi,

I have a switch 4500 as a Core and dhcp server. In this I have a dhcp pool for the vlan 111.

I have an other switch, 3560. In this I have one port assigned to the vlan 111. When I connect a computer to this port, the computer get a ip, but I can ping the gateway. I look for the computer's mac address with "sh mac address-table" command and I find the mac with the port, but if I look for the same mac in the "core" with the "sh ip dhcp bind" command, I realize that the mac is diferent:

siwtch access:

access(config-if)#do sh mac add | include Gi0/1

      111    2c41.380f.60cf    DYNAMIC     Gi0/1

switch core:

core0#sh ip dhcp bi

     192.168.111.124     012c.4138.0f60.cf       Oct 24 2013 12:14 AM    Automatic

the problem is only with two computers in all the ports of this switch, but if I connect the same computer in other switch in the same LAN it works without problems.

Do you have any idea??

I think the dhcp pool is properly configured because with others computers in other port with the same vlan works perfect!!!



Everyone's tags (3)
7 REPLIES
VIP Purple

Re: DHCP & port connection problem

Hi try this command to cleAr DHCP bindings:
Clear ip dhcp bind A.B.C.D

And then check it again with
Show ip dhcp bind


Regards

Sent from Cisco Technical Support iPhone App

Re: DHCP & port connection problem

Hi,

I have already tried with this command, but is the same. The mac address and the ip are the same.

Thanks

Sent from Cisco Technical Support iPhone App

Community Member

Re: DHCP & port connection problem

What is the exact interface configuration?

Re: DHCP & port connection problem

Switchport mode access
Switchport access vlan 111
Switchport voice vlan 140

Before this conf, I had a portsecurity with max 2 and I realized that the port was in err-disable.

But now that the port only has the vlan voice and the vlan access configuration, the port isnt in err-disable but it doesnt work.

Thanks

Sent from Cisco Technical Support iPhone App

Silver

Re: DHCP & port connection problem

Hi Carlos,

are you, by any chance, running any multicast?

Because this seems like multicast mac-address (If im correct, it starts with 01) doubt it is a valid host's mac address.

core0#sh ip dhcp bi

     192.168.111.124     012c.4138.0f60.cf

Best regards,

Jan

Re: DHCP & port connection problem

Hi,

Yes I have a IPICS connected to the 4500.

But this mac address is a computer. Is it normal that appears lile this?

And why it cant ping to its gateway?

Sent from Cisco Technical Support iPhone App

Silver

DHCP & port connection problem

Hi Carlos,

I am sorry, but the MAC addresses are the same and that is not multicast address, my mistake.

The first two numbers are media type (ethernet, in your case)

http://www.freesoft.org/CIE/RFC/1700/24.htm

  2c41380f60cf access sw
012c41380f60cf core sw

access(config-if)#do sh mac add | include Gi0/1

      111    2c41.380f.60cf    DYNAMIC     Gi0/1

switch core:

core0#sh ip dhcp bi

     192.168.111.124     012c.4138.0f60.cf       Oct 24 2

So the problem is somewhere else, the mapping is correct.

Best regards,

Jan

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