Ethernet Switching
Ethernet Switching

duplicated ip addresses from the dhcp pool

[ Edited ]
‎08-25-2019 04:18 PM

Hi there,

It has been took for ages to get diplayed the following output. Like 2200ex is not gonna response..... And secondly what reason 2 different ip addresses in associated dhcp pool in the same vlan is assigning to the same machine(windows) ? Any ideas and approaches to fix this predicument duplicated ip issues...

 

 

ex200> show arp | match 7f:9e
b0:b9:8b:55:7f:9e      10.119.136.30      10.119.136.30       vlan.121   none
b0:b9:8b:55:7f:9e     10.119.136.139    10.119.136.139      vlan.121   none

 

Thx

A.

3 REPLIES 3
Ethernet Switching

Re: duplicated ip addresses from the dhcp pool

‎08-25-2019 04:52 PM

@Arix,

 

Try to check "show arp no-resolve | match 7f:9e" and confirm if that's faster? By default, system tries to resolve the corresponding hostname.  See: https://kb.juniper.net/InfoCenter/index?page=content&id=KB17270&cat=ARP&actp=LIST

 

Regarding two IPs, this does mean the client has responded to ARP request with two different IPs.  Is the DHCP pool on the EX? You can consider using DHCP snooping and ARP inspection to avoid this.

https://www.juniper.net/documentation/en_US/junos/topics/concept/port-security-dhcp-snooping-els.htm...

https://www.juniper.net/documentation/en_US/junos/topics/task/configuration/understanding-and-using-...

 

Also ensure no proxy arp set on any L3 device in the same network.

 

Hope this helps.

 

Regards,
-r.

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Ethernet Switching

Re: duplicated ip addresses from the dhcp pool

[ Edited ]
‎08-25-2019 05:41 PM

Hi mriyaz,

Thanks for the reply.

 

Dhcp sits on the ex 2200 L3 device....  clients-------ex2200 L2------------>L3 ex2200 -g/w-------->out

 

Yes you are right....When using the "show arp no-resolve | match <mac addr> is faster.... Thanks for this tip...

 

How about it is acceptible  when assining an spesific IP address from the associated dhcp pool that sits on L3 ex2200  to specific window user? Because user needs to know that specific ip addr all the time?

 

Thx

Ar

Ethernet Switching

Re: duplicated ip addresses from the dhcp pool

‎08-25-2019 09:00 PM

Welcome Arix!

 

Yes we can bind a known IP to a user MAC address, please find the reference CLI here:

https://www.juniper.net/documentation/en_US/junos/topics/example/configuring-static-dhcp-ip-addresse...

 

 

Hope this helps.  Please mark the post so others could benefit from your query Smiley Happy.

 

Regards,
-r.

--------------------------------------------------

If this solves your problem, please mark this post as "Accepted Solution."
Kudos are always appreciated Smiley Happy.