From: Reza Toghraee (reza@toghraee.com)
Date: Sat Oct 18 2008 - 19:37:11 ART
Hello
I tested this scenario and now its working.
Let me show you my configuration on CAT1 :
ip dhcp snooping vlan 30
no ip dhcp snooping information option
ip dhcp snooping database flash:snoop.txt
ip dhcp snooping
!
interface FastEthernet0/4
switchport access vlan 30
switchport mode dynamic desirable
ip dhcp snooping trust
!
CAT12#sh ip dhcp snooping
Switch DHCP snooping is enabled
DHCP snooping is configured on following VLANs:
30
Insertion of option 82 is disabled
circuit-id format: vlan-mod-port
remote-id format: MAC
Option 82 on untrusted port is not allowed
Verification of hwaddr field is enabled <<<<<<============= I think
this is the ISSUE. Seems by default its Enable.
Interface Trusted Rate limit (pps)
------------------------ ------- ----------------
FastEthernet0/4 yes unlimited
CAT 3
Rack1SW3(config-if)#do show run int vlan 30
Building configuration...
Current configuration : 58 bytes
!
interface Vlan30
ip address dhcp client-id Vlan30
end
by default CAT1 , compares the source MAC address of the DHCP frame with the
client-id inside the DHCP request.
By default the client ID is something crazy long, but after I changed to MAC
it fixed. (ip address dhcp client-id Vlan30).
Regards
Reza Toghraee
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
Hobbs
Sent: Saturday, October 18, 2008 11:56 PM
To: Cisco certification
Subject: dhcp snooping
Hello,
I have the following topology:
[R4]------[CAT1]----trunk----[CAT2]----SVI (vlan 30)
R4 is a dhcp server in vlan 30, connected to CAT1 f0/4.
CAT2 has an SVI for vlan 30, with ip address assigned via dhcp.
This works great.
Now when I set up dhcp snooping on CAT1 it fails. On CAT1 I do the
following:
ip dhcp snooping
ip dhcp snooping vlan 30
int f0/4
ip dhcp snooping trust
This still prevents CAT2 from getting an IP address from R4....is there
something I am missing?
http://www.cisco.com/en/US/docs/switches/lan/catalyst3560/software/release/1
2.2_44_se/configuration/guide/swdhcp82.html#wp1180910
thanks,
Blogs and organic groups at http://www.ccie.net
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