IP helper on L3 switch?

Unanswered Question
Jun 22nd, 2010


I have 4 x 3750 switches that are trunk together, ther are a few VLAN's and on VLAN 10 I have a DHCP server that issues out IP's to VLAN 10, but I now need to use this server to issue IP's to PC that are on VLAN 20 and 30, how can I do this?

I am using EIGRP routing on the 4 switches so all the VLAN's can route to each other.


I have this problem too.
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Andy White Tue, 06/22/2010 - 07:21

Thanks, out of interest what is the best way to route between vlans on L3 switches, and should the users gateway normally be the IP of there VLAN?

francisco_1 Tue, 06/22/2010 - 07:27


users should use their vlan SVI as their local default gateway to route to another vlan.


SANTHOSHKUMAR S... Tue, 06/22/2010 - 07:22

Hi Andy

      Do u have L3 SVI for your VLAN on ur switch ??? , If u have defined all 3 VLAN as L3 SVI in ur Switch then only give ip helper address comand under interface vlan 20 & 30 ,

eg :

     Interface vlan 10

      ip address


       Interface vlan 20

      ip address

      ip helper address

       Interface vlan 30

      ip address

      ip helper address

Condition all switches connect Via trunk port should permit VLAN 10 , 20 ,30 ...

Andy White Tue, 06/22/2010 - 07:26

How would I configure SVI's so all VLAN's can route between each other?

Should the gateway of the PC's be the VLAN IP?


SANTHOSHKUMAR S... Tue, 06/22/2010 - 07:33

Andy ,

           while u define ur default router in ur DHCP scope u can point to interface of L3 SVI interface

for eg : default router : 192.1681.1 for vlan 10

           default router : for vlan 20

           default router : for vlan 20

that will carry traffic to SVI interface , then it will use ur routing table for ur l3 switch  packet exit ...




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