here i used the recommendations of making the DHCP server an external server and just use the command IP helper X.X.X.X in cisco 4500X under each interface vlan to relay DHCP to hosts in this vlan , so that i can get IP on the host machine but when i try to ping machine in other vlan which also obtain its ip from this DHCP server , ping is time out . when i disable ip helper command and make my core switch as DHCP server for each vlan ,inter-vlan routing work probably and i could ping remote host in other vlans .
note i did same configuration on the DR site on cisco 4506 core switch and it's work probably.

  • 1
    Can you post both configurations?
    – Ron Trunk
    Sep 7, 2015 at 1:45
  • You could improve your question by editing it to add more details. You may find our Question Checklist helpful when editing your question. For example: configurations, network diagram, vendor/model of devices, software versions, etc.
    – YLearn
    Sep 7, 2015 at 4:55
  • @ Ron Trunk i'm sorry unfortunately i removed the IP helper configurations and i did DHCP server on the core switch
    – Gadeliow
    Sep 7, 2015 at 7:29
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    – Ron Maupin
    Aug 6, 2017 at 21:17

2 Answers 2


IP helper should not make any routing difference , so you need to check the provided IP settings by DHCP if it is right or not , you need to check two things:

  1. Default Gateway for each DHCP Scope
  2. subnet mask for each scope
  • in the first case with ip helper configurations i checked the pc ip configurations , i found it obtained the IP , subnet , default GW , DHCP server and DNS all probably so no problem with default GW or Subnet mask
    – Gadeliow
    Sep 7, 2015 at 7:31

you can do a simple test to check the routing part independently of dhcp configuration.

try to fix an IP on one host and ping the DHCP Server @, if you can reach it => the routing part is ok.

the second part is to check if the DHCP server is working correctly.

configuration of ip helper under SVI is pretty simple on 4500x mainly if you are using VSS technology

Int vlan X ip dhcp-helper XXXXX

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