Configure Ip Helper on Cisco Switch

[FN-GM]

Hi,

 

I am not very familiar with Cisco kit so pleas bare with me.

 

I would like to change the IP helper users on VLAN 200

 

From what i understand to do this i need to telnet into the core switch and enter the following

 

switchname#interface vlan 200
switchname#ip address x.x.x.x 255.255.255.0
switchname#ip helper-address x.x.x.x

 

On the second line where you specify the IP address what do you enter there please? What IP address are they after please?

 

Also will these commands remove the old IP helper details please?

 

Thanks

[ChrisH]

The ip address is the address of that vlan eg the ones all the clients on that vlan will use as their default gateway. So you shouldn't need to change it unless your completely changing ranges.

[FN-GM]

The ip address is the address of that vlan eg the ones all the clients on that vlan will use as their default gateway. So you shouldn't need to change it unless your completely changing ranges.

 

That makes sense, why didnt i think of that . Can i miss that line out or do i have to include it?

 

Also will the remove the old helper setting please?

 

Thanks

[ChrisH]

To undo most cisco commands you usually do the same command but put "no " in front.

[FN-GM]

Ok so i would do the following?

 

switchname#interface vlan 200
switchname#ip address x.x.x.x 255.255.255.0
switchname#ip no helper-address 
switchname#ip helper-address x.x.x.x

 

Thanks

[FN-GM]

Anyone before i give this a bash please?

 

Do i need to specify the ip address as its already set?

 

Thanks

[cpjitservices]

Just enter the command: ip helper-address followed by the address of the machine you want the broadcasts to be forwarded to, address = Destination broadcast or host address to be used when forwarding UDP broadcasts. There can be more than one helper address per interface.

[Willott]

If you no longer need the previous ip helper, then you should do:

 

no ip helper-address xxx.xxx.xxx.xxx

 

(where xxx.xxx.xxx.xxx is old ip helper)

 

This may protect you should someone stick something running on the old IP which responds to the broadcast received.

[FN-GM]

Hi,

 

As i dont do this often, how would i go about viewing the current ip-helper on a VLAN please? I knew this 6 months ago and for the life of me i cant remember.

 

Thanks

[dan41322]

Hi,

 

As i dont do this often, how would i go about viewing the current ip-helper on a VLAN please? I knew this 6 months ago and for the life of me i cant remember.

 

Thanks

 

I am pretty sure you can find this if you do the show running config command. You need to be in enabled mode to do this not in conf t mode. Does that help any?

[FN-GM]

I had a look in there but it only showed the config for 1 of our 5 vlans. I have not worked at the school for 8 months i forgot how it was setup.

 

Thanks

[dan41322]

I had a look in there but it only showed the config for 1 of our 5 vlans. I have not worked at the school for 8 months i forgot how it was setup.

 

Thanks

 

I'll have a look in my ccna book tomorrow for you when I get to work if no one else has replied to your post by then to see if I can find anything for you. I would have thought it would be in the show running config though? Usually most info is in there.

[FN-GM]

Thanks

[dan41322]

Heya,

Just to let you know that I tried the sh running-config and managed to get the IP Helper address on one of my devices here:

[FN-GM]

The setup they have here is weird, long story why. Might i need to configure the IP helper on another switch if it isnt showing in my running config?

 

Thanks

[dan41322]

Are you on the switch that should have the IP Helper address configured?

[CISCODISCO]

Hello,

 

If you have already configured the default gateway on the interface there is no need in re-entering the configuration you will just need to enter the ip helper-address- the ip address where you want the broadcasts to be forwarded i.e DHCP Server.

 

The command will bring up the entire configuration entered and running on the Cisco IOS including IP Helper. A more specific command to use would be .

 

The setup they have here is weird, long story why. Might i need to configure the IP helper on another switch if it isnt showing in my running config?

 

Thanks

 

No the running configuration is local only if it is not showing it means it has not been configured on that switch.

 

HTH

 

Edited March 29, 2012 by CISCODISCO

[nannook215]

The setup they have here is weird, long story why. Might i need to configure the IP helper on another switch if it isnt showing in my running config?

 

Thanks

depending on your setup you may or may not have to configure Ip fowarding/ip helper on any number of switches if they are daisychained depending on how many switches the broadcast have to go through to get to the final network destination

switch that doesn't requireit would be last switch in the chain