Re: Configuring dhcp on cisco 3750

On Oct 2, 8:00 pm, Trendkill <jpma...@xxxxxxxxx> wrote:
On Oct 2, 7:41 pm, Trendkill <jpma...@xxxxxxxxx> wrote:



On Oct 2, 7:39 pm, Asif <asif.haswa...@xxxxxxxxx> wrote:

On Oct 2, 4:29 pm, Trendkill <jpma...@xxxxxxxxx> wrote:

On Oct 2, 6:48 pm, Asif <asif.haswa...@xxxxxxxxx> wrote:

I've been trying to configure a simple dhcp setup with the following
topology:

Cisco3750[Port:1] <---> dhcp server 192.168.2.100
Cisco3750[Port:3-5] <---> dhcp clients

I am using tetheral on the dhcp server 192.168.2.100 interface to look
for dhcp requests and the proceeding dhcp traffic.
This is not working!
I connected one of the clients to the dhcp server back-2-back to
verify that dhcp works.
Am I missing something?
I want this to be really simple!
Can anyone help, please?

Here is my cisco3750 running config:

Current configuration : 2208 bytes
!
version 12.2
no service pad
service timestamps debug uptime
service timestamps log uptime
no service password-encryption
!
hostname Switch
!
enable secret 5 $1$iC8.$yNpSaeY3mfGX16BA7mS5d/
enable password qlogic
!
no aaa new-model
switch 1 provision ws-c3750g-24ts
vtp mode transparent
ip subnet-zero
!
ip dhcp snooping vlan 2
!
!
!
no file verify auto
spanning-tree mode pvst
spanning-tree extend system-id
!
vlan internal allocation policy ascending
!
vlan 2
name vlan-dhcp
!
!
interface GigabitEthernet1/0/1
switchport access vlan 2
switchport mode access
ip dhcp snooping trust
!
interface GigabitEthernet1/0/2
switchport access vlan 2
switchport mode access
ip dhcp snooping trust
!
interface GigabitEthernet1/0/3
switchport access vlan 2
switchport mode access
ip dhcp snooping trust
!
interface GigabitEthernet1/0/4
switchport access vlan 2
switchport mode access
ip dhcp snooping trust
!
interface GigabitEthernet1/0/5
switchport access vlan 2
switchport mode access
ip dhcp snooping trust
!
interface GigabitEthernet1/0/6
!
interface GigabitEthernet1/0/7
!
interface GigabitEthernet1/0/8
!
interface GigabitEthernet1/0/9
!
interface GigabitEthernet1/0/10
!
interface GigabitEthernet1/0/11
!
interface GigabitEthernet1/0/12
!
interface GigabitEthernet1/0/13
!
interface GigabitEthernet1/0/14
!
interface GigabitEthernet1/0/15
!
interface GigabitEthernet1/0/16
!
interface GigabitEthernet1/0/17
!
interface GigabitEthernet1/0/18
!
interface GigabitEthernet1/0/19
!
interface GigabitEthernet1/0/20
!
interface GigabitEthernet1/0/21
!
interface GigabitEthernet1/0/22
!
interface GigabitEthernet1/0/23
!
interface GigabitEthernet1/0/24
!
interface GigabitEthernet1/0/25
!
interface GigabitEthernet1/0/26
!
interface GigabitEthernet1/0/27
!
interface GigabitEthernet1/0/28
!
interface Vlan1
ip address 172.17.141.150 255.255.254.0
no ip route-cache
no ip mroute-cache
shutdown
!
interface Vlan2
ip address 192.168.2.150 255.255.255.0
ip helper-address 192.168.2.100
!
ip default-gateway 172.17.140.1
no ip classless
no ip route static inter-vrf
no ip http server
!
!
!
control-plane
!
!
line con 0
line vty 0 4
password qlogic
login
line vty 5 15
password qlogic
login
!
!
end

Switch#show vlan

VLAN Name Status Ports
---- -------------------------------- ---------
-------------------------------
1 default active Gi1/0/6, Gi1/0/7,
Gi1/0/8
Gi1/0/9, Gi1/0/10,
Gi1/0/11
Gi1/0/12, Gi1/0/13,
Gi1/0/14
Gi1/0/15, Gi1/0/16,
Gi1/0/17
Gi1/0/18, Gi1/0/19,
Gi1/0/20
Gi1/0/21, Gi1/0/22,
Gi1/0/23
Gi1/0/24, Gi1/0/25,
Gi1/0/26
Gi1/0/27, Gi1/0/28
2 vlan-dhcp active Gi1/0/1, Gi1/0/2,
Gi1/0/3
Gi1/0/4, Gi1/0/5
1002 fddi-default act/unsup
1003 trcrf-default act/unsup
1004 fddinet-default act/unsup
1005 trbrf-default act/unsup

VLAN Type SAID MTU Parent RingNo BridgeNo Stp BrdgMode
Trans1 Trans2
---- ----- ---------- ----- ------ ------ -------- ---- --------
------ ------
1 enet 100001 1500 - - - - -
0 0
2 enet 100002 1500 - - - - -
0 0
1002 fddi 101002 1500 - - - - -
0 0

VLAN Type SAID MTU Parent RingNo BridgeNo Stp BrdgMode
Trans1 Trans2
---- ----- ---------- ----- ------ ------ -------- ---- --------
------ ------
1003 trcrf 101003 4472 1005 3276 - - srb
0 0
1004 fdnet 101004 1500 - - - ieee -
0 0
1005 trbrf 101005 4472 - - 15 ibm -
0 0

VLAN AREHops STEHops Backup CRF
---- ------- ------- ----------
1003 7 7 off

Remote SPAN VLANs
------------------------------------------------------------------------------

Primary Secondary Type Ports
------- --------- -----------------
------------------------------------------

Switch#show ip dhcp snoop
Switch DHCP snooping is disabled
DHCP snooping is configured on following VLANs:
2
Insertion of option 82 is enabled
Option 82 on untrusted port is not allowed
Verification of hwaddr field is enabled
Interface Trusted Rate limit (pps)
------------------------ ------- ----------------
GigabitEthernet1/0/1 yes unlimited
GigabitEthernet1/0/2 yes unlimited
GigabitEthernet1/0/3 yes unlimited
GigabitEthernet1/0/4 yes unlimited
GigabitEthernet1/0/5 yes unlimited

Why do you have an IP-helper on VLAN 2? While I would think this
wouldn't hinder anything, I would definitely remove that first,
especially since the switch sees those frames before anything else.....

At first I did a shutdown cmd on the default vlan 1 and simply
connected
the dhcp server and the clients. I did not configure the helper-
address though.
Then I decided that I want an isolated subnet, in which I want to
perform
dhcp operations. All this is for testing network boot by-the-way. So
now I
have the vlan #2 (192.168.2.x). By-the-way, when I looked at the cisco
docs
and used the ip helper-address cmd, the directions were to configure
the helper-address
per vlan. I tried do the helper-address per interfaces connected to
the clients and this
is unsupported by the cisco f/w I have 12.2(25)SEB4.

Ip-helper is only needed for subnets that do not have a directly
connected dhcp server. Additionally, you are saying your dhcp server
is .100, and your ip-helper says .150. I would either make that
match, or get rid of it, especially since these clients are on the
same vlan. Let me know how you fare and we can move to the next phase
of looking at your issue.

I'm sorry, the helper address does match. Regardless, you shouldn't
need it on the same vlan as the dhcp server, so I'd still try to
remove and test. Additionally, your show ip int brief show all ports
as up/active as needed?

Ok, I saw your latest post. Can you ping the dhcp server from the
switch? What happens when you do an extended ping (and choose a
source interface of the VLAN 2 IP address)? If ping is successful,
can you try to set one of the clients to a hard coded IP and do the
same test? Can you ping between the static IPed client and the dhcp
server? Does show mac-address-table show macs for the clients when
they first connect as they should?

.

Relevant Pages

  • Cisco pix 535 and Catalyst solutions
    ... interface gb-ethernet0 1000auto shutdown ... fixup protocol dns maximum-length 512 ... switchport trunk native vlan 3 ...
    (comp.dcom.sys.cisco)
  • Re: Configuring dhcp on cisco 3750
    ... for dhcp requests and the proceeding dhcp traffic. ... I connected one of the clients to the dhcp server back-2-back to ... interface GigabitEthernet1/0/1 ...
    (comp.dcom.sys.cisco)
  • Re: Configuring dhcp on cisco 3750
    ... switch does not have to do anything for DHCP to work. ... DHCP snooping is a DHCP security feature that provides security by filtering ... interface GigabitEthernet1/0/1 ... switchport access vlan 2 ...
    (comp.dcom.sys.cisco)
  • Re: Configuring dhcp on cisco 3750
    ... VLAN 2 contains a DHCP server and several client computers. ... I am using tetheral on the dhcp server 192.168.2.100 interface to look ... switchport access vlan 2 ...
    (comp.dcom.sys.cisco)
  • Re: Configuring dhcp on cisco 3750
    ... for dhcp requests and the proceeding dhcp traffic. ... I connected one of the clients to the dhcp server back-2-back to ... interface GigabitEthernet1/0/1 ... switchport access vlan 2 ...
    (comp.dcom.sys.cisco)