IP Helper-address VLAN

[SathishkumarSaravanan0348]

Hello Experts,

Could you please answer for my general question for the below requirement.

Requirement: It is to remove the existing helper-address in the vlan and to add the new helper-address in the vlan. 

Assume the request is to remove the helper address (10.67.65.4) from VLAN 3 and to add the new helper (10.99.52.8).

existing running config for vlan 3:

#sh run int vlan 3

interface vlan 3

description ***General***

ip helper-address 10.78.99.5

ip helper-address 10.88.87.2

ip helper-address 10.67.65.4------> this helper need to be removed and add the new one.

Findings:

There are end users connected to the vlan 3 and we are learning the arp entries.

Question:

Does this kind of change require an downtime from the end users or it wont cause any outage, as there are 3 inflobox server(helper address) configured in it?

Thanks.

[Mark Elsen · Accepted solution]

 - Use these configuration commands :

         int vlan 3

            no ip helper-address 10.67.65.4

            ip helper-address new-ip-here

               There will be no downtimes involved

 M.

[SathishkumarSaravanan0348]

Thanks for the reply.

[balaji.bandi · Accepted solution]

Adding or removing p helper-address not cause any issue, if the order is 3 is the least priority - since it checks 1 and 2 and then 3 so on.

some time end device not able to reach 3 due to TTL. 

removing adding you can do below :

interface vlan 3

description ***General***

ip helper-address  XXXXXXX  << adding new one 

no ip helper-address 10.67.65.4   <<--removing

but if you like to change the order, you need to remove and add all based on the order as below example :

interface vlan 3

description ***General***

no ip helper-address 10.78.99.5

no ip helper-address 10.88.87.2

no ip helper-address 10.67.65.4

ip helper-address DHCPserver1

ip helper-address DHCPserver2

ip helper-address DHCPserver3

[SathishkumarSaravanan0348]

Thanks a lot for the reply. Got your answer.