Forwarding DHCP requests over 802.1q trunk on ASA5505

Answered Question
May 16th, 2007
User Badges:

We are running an ASA5505 with ip plus licensing, which allows us to run multiple vlans (in our case 3: outside, data, and voice). The data and voice vlans (both same security levels) members of an 802.1q trunk on eth0/4, passing the voice and data vlans through the trunk to a 3750 switch.

Our DHCP server resides in the data lan. Is there an equivalent command on the ASA's to the Cisco router command "ip helper-address x.x.x.x" that needs to be placed on the ASA voice interface vlan (svi) to pass these dhcp requests? If not how do we get the dhcp requests to pass through the ASA? FYI the "same-security-traffic permit inter-interface" and "same-security-traffic permit intra-interface" are configured on the firewall.

We do not see any entries in our dhcp server scopes for the Cisco phones, but the phones are registered to the off subnet Call Mgr and are using addresses in the range of the voice dhcp scope on the server.

Odd one for sure....any help is appreciated.


Correct Answer by ggilbert about 10 years 1 month ago


Is this what you are looking for:

dhcprelay server

dhcprelay enable

dhcprelay timeout 90

Check out that link given below:

Rate this post, if it helps.



  • 1
  • 2
  • 3
  • 4
  • 5
Overall Rating: 5 (1 ratings)
swharvey Thu, 05/17/2007 - 08:09
User Badges:

Yes it is. I got this information from a tac engineer priory to your post but your response is identical and correct and resolved my issue.

Many thanks,


ggilbert Thu, 05/17/2007 - 08:24
User Badges:
  • Cisco Employee,

Thanks for letting me know, scott.

Much appreciated!



This Discussion