Cisco Support Community
cancel
Showing results for 
Search instead for 
Did you mean: 
Announcements
Webcast-Catalyst9k
New Member

Problems to receive IPs address from DHCP server with multiple scopes

HI all !

End user has a WS-C3560G-48TS-S  with c3560-ipbase-mz.122-50.SE5 as switch CORE where intervlan routing is set.

A windows DHCP server with 3 scopes has been configured and is conected to port 8 in switch core.


At the beginning all user and server were in vlan 1 (172.16.30.X) then  end user requested to separate network segment;new vlan were set for  servers, user, wlans user. In windows DHCP server were defined new scopes for 172.16.33.X, 172.16.35.X


When I try to moved user to 17.16.33. X or 172.16.35.X ( previously the switch port are configured  in new vlan)they don´t get

ip address of new segment, some time  receive ip address (169.x.x.x) , other times the original segment 172.16.30.X.
just in few times  new segments are assigned correctly to ports.

My doubt is,

is there something left in switch's configuracion?
the switch's port where windows DHCP  server is connected required an special config?
maybe something wrong in configuration with windows DHCP server (I checked that new scopes are set and active)?

any suggestion for this issue?

thanks in advance for your help

*****************************************************************

ip routing

!
interface Vlan300
description  SERVER
ip address 172.16.30.30 255.255.255.0
ip helper-address 172.16.30.1
!

interface Vlan320
description Mgmt
ip address 172.16.32.254 255.255.255.0
!
interface Vlan330
description Users
ip address 172.16.33.253 255.255.255.0
ip helper-address 172.16.30.1

interface Vlan350
description WLAN_Users
ip address 172.16.35.253 255.255.255.0
ip helper-address 172.16.30.1

interface GigabitEthernet0/8
description SERVER DHCP
switchport mode access
switchport access vlan 300

interface GigabitEthernet0/X
description users
switchport mode access
switchport access vlan 330


interface GigabitEthernet0/X
description users
switchport mode access
switchport access vlan 350

21 REPLIES
Hall of Fame Super Blue

Re: Problems to receive IPs address from DHCP server with multip

Providing your DHCP server is 172.16.30.1 then there doesn't seem to be anything obviously wrong with your config. By the way you don't need an ip helper-address on the iinterface for vlan 300 because the DHCP server would see broadcasts from clients in that vlan anyway.

I would be looking at the DHCP server setup.

Edit - i'm assuming the new vlans were created at L2 as well ie. does a "sh vlan brief" show the new vlans ?

Jon

New Member

Re: Problems to receive IPs address from DHCP server with multip

Hi Jon,

thanks for your quick response .

All vlans were created and are active ( in this info the new vlans are not associted to the switch's  port I shown previously, because a return to vlan 1)

Unfortunately I'm not specialist in windows server so I can't confirm if the config of multiple scopes is wrong or there is somethinng left. I just reviewed general config of the new scopes and that were active.

thanks for you tip for vlan 300

SW#sh vlan brief

VLAN Name                             Status    Ports
---- -------------------------------- --------- -------------------------------
300  Servidores                   active
310  VoIP                         active
320  Mgmt                         active
330  Users                        active
340  Reserva                          active
350  WLAN_Users                   active
1002 fddi-default                     act/unsup
1003 token-ring-default               act/unsup
1004 fddinet-default                  act/unsup
1005 trnet-default                    act/unsup
SW#

Hall of Fame Super Blue

Problems to receive IPs address from DHCP server with multiple s

Thanks for the output.

I would pick a test PC, do an "ipconfig /release" on it and then allocate it into the new vlan and try an ipconfig /renew" . There is nothing else that you have configured on the switch that could be confusing the issue is there ?

Jon

New Member

Problems to receive IPs address from DHCP server with multiple s

Hi jon

I really appreciate your time.

We have alredy tried that option and others

ipconfig /release  then  ipconfig /renew

disconnect the cable

disable the interface and enable once again

reset the PC or lap

any of this works

regards

Hall of Fame Super Blue

Problems to receive IPs address from DHCP server with multiple s

Okay, if you post the config we can check if there is anything there that could be causing the problem.

So you have -

1) ipconfig /release on PC. Check that PC has no IP.

2) on the switch allocate that PCs port into the new vlan

3) check that the L3 inertface for the new vlan is up/up (sh ip int brief | include Vlan)

4) ipconfig /renew on the PC

If you have done in it this order then please ignore.

Jon

VIP Super Bronze

Problems to receive IPs address from DHCP server with multiple s

Hi Filiberto,

I would go back to the servers guys and asked them if they have configured the scopes correctly with correct gateways?

Also, rebooting the server may help too.

HTH

New Member

Problems to receive IPs address from DHCP server with multiple s

Hi Reza,

the new scopes includes ip address of default gateways correctly

regards

New Member

Problems to receive IPs address from DHCP server with multiple s

As some one has mentioned that you don't need "ip helper-address 172.16.30.1" under vlan 300, please take this line out. I assume clients are MS windows based then it should be the issue with the DHCP server. Make sure the "DCHP server"service is up and running on the server and proper scope is configured.

Thanks,

New Member

Problems to receive IPs address from DHCP server with multiple s

Hi sajid,

DHCP service is up and running, the original segment is assigned correctly the news ones no

regards

Hall of Fame Super Blue

Re: Problems to receive IPs address from DHCP server with multip

When you only had one vlan and scope what was the subnet and subnet mask for that scope ?

Edit - the scopes have been activated haven't they ?

Jon

New Member

Re: Problems to receive IPs address from DHCP server with multip

Hi jon,

this is the config after setting L3 interfaces and before moving user to vlan 300 or 350

      

the original subnet is 172.16.30.X 255.255.255.0

regards

Hall of Fame Super Blue

Re: Problems to receive IPs address from DHCP server with multip

If this is still in your config 

ip default-gateway 172.16.30.249

can you remove it and add the following and then retest -

no ip default-gateway 172.16.30.249

ip route 0.0.0.0 0.0.0.0 172.16.30.249

Jon

New Member

Re: Problems to receive IPs address from DHCP server with multip

Hi Jon

I have already tried static route  0.0.0.0 0.0.0.0 172.16.30.249.

During these days I was looking up in microsoft forum about this issue, I found many cases exactly like this, unfortunately

any of them said if they solved this issue, microsoft specialist state that is a problem from cisco side :-(.

regards

Hall of Fame Super Blue

Problems to receive IPs address from DHCP server with multiple s

Have you done DHCP debugging on the switch when the PC tries to get an address ?

What OS is running on the client PCs ?

Jon

New Member

Re: Problems to receive IPs address from DHCP server with multip

Hi Jon,

I reproduce a similar scenario as end user has. After doing DHCP debugging on  access switch I notice that vlans did not pass through trunk with sw core, even though it looks trunk were UP.

Finally I could set the trunk UP and verify that vlans can go through the trunks.  I set differents ports in differents VLANs and I  connected my lap to those differents ports; laps received ip address from differents  vlan without any problem. I did not need to force to release ip address.

It was a simple detail that  was about to make me crazy....

thanks for your time

regards

Hall of Fame Super Blue

Problems to receive IPs address from DHCP server with multiple s

No problem, glad you got it sorted and thanks for letting us know the solution.

Jon

New Member

Re:Problems to receive IPs address from DHCP server with multipl

I think the problem could be with Ip address helper.


Sent from Cisco Technical Support Android App

New Member

Re: Problems to receive IPs address from DHCP server with multip

HI luke,

the ip  address is correct, there is only one DHCP server.

regards

New Member

Re: Problems to receive IPs address from DHCP server with multip

Hi,

As per the above config,you should be able to ping all ip address of the vlans in your core switch(L3 Switch).Verify once.

After verifying,you do the following in your DHCP Server.

Go to Command prompt,Type

route add vlan address mask IPV4 Subnet Mask Core switch address(where you have created Vlans) -p(persistant Route)

Eg route add 172.18.0.0 mask 255.255.0.0 172.16.1.1 -p

Once the vlan traffic is generated and it is sent to l3 switch or for the default gateway.

If the gateway is firewall and if their is no ploicy defined for that,then packet gets lost.

If the gateway is L3 or core switch,the packet will be delivered to dhcp server,but the dhcp server will send to default gateway.

By adding this command,we are defining return path for the traffic,rather than traffic flowing through default gateway of that vlan.

After adding persistant route,Your DHCP Server will be able to ping all vlans.

Regards,

Guru

New Member

Re: Problems to receive IPs address from DHCP server with multip

Hi,

Put your user subnet,user subnet mask and your server vlan gateway (which is in core switch) to the route.

Regards,

Guru

New Member

Problems to receive IPs address from DHCP server with multiple s

Hi,

Check the ports connected between the Multilayer switch and the access switches and make sure that they are trunk ports and VLANs are allowed on the trunk and the PCs are connected to access ports with corresponding access VLANs.

P.S there is no need to ip helper-address on the interface VLAN 300 where the DHCP exists.

Regards,

Khaled Omar

Regards, Khaled Omar "Please don't forget to rate useful posts"
999
Views
7
Helpful
21
Replies
CreatePlease to create content