From: Murphy, William (William.Murphy@uth.tmc.edu)
Date: Thu Mar 27 2008 - 13:12:13 ART
In our environment our DHCP servers do not support option 82 so we found that we had to put "no ip dhcp snooping information option" on our switches to make DHCP work consistently...
Bill Murphy
Senior Network Analyst
University of Texas Health Science Center - Houston
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of Haukur ^srparson
Sent: Sunday, March 23, 2008 5:01 PM
To: Geert Nijs; ccielab@groupstudy.com
Subject: RE: DHCP snooping and ip helper interaction
Hi Geert,
If you add the "ip dhcp relay information trusted" on the interface on the distribution switch the DHCP service should start working again, this command allows the L3 interface to forward packets that include DHCP Option 82 informations.
R.
Haukur
CCIE#18026
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of Geert Nijs
Sent: 22. mars 2008 15:33
To: ccielab@groupstudy.com
Subject: DHCP snooping and ip helper interaction
All,
Does a DHCP snooping configuration NEED an ip helper address defined on the
same switch ?
In my lab setup, DHCP breaks when i configure dhcp snooping without ip helper
address.
Setup:
Access = C3750 , 12.2(25)SE2
Distribution= C6500, sup720, 12.2(18)SXF8
ACCESS
int vlan 100
ip address 1.1.1.250 255.255.255.0 <- for management of the
switch !
int gi1/0/49 <--- uplink (is dhcp trusted)
ip dhcp trust
ip dhcp snooping vlan 100 <- activate snooping
on access
DISTRIBUTION
int vlan 100
ip address 1.1.1.2 255.255.255.0
standby 1 ip 1.1.1.1
ip helper-address 192.168.1.1
Without dhcp snooping on the access, the config works. Clients get an ip
address.
Once i enable dhcp snooping on the access, dhcp doesn't work anymore ??
regards,
Geert Nijs
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