DHCP problem

[YenLin]

Hi all, I am doing ip migration, but I am experiencing a dhcp problem. We've got a lot of vlans and many routers inside of our lan network.

I configed vlan 2040 as management vlan at edge switch and primary-vlan 2040.

However, I was trying to connect pc/nb to other vlan, For example: vlan 2001, vlan 2020, but with no luck.

Only client untag on vlan 2040 will work or switch config ip add dhcp will get assigned an ip address.

Can any one guide me, any configuration error from my example switch, pls?

It is attached as attachment.

[Vince_Whirlwind]

I think you need to be more specific than, "no luck". Is it an issue of network configuration or DHCP configuration?

Can the PC ping its default gateway, if you give it an IP address?

Has that DHCP scope been tested and been shown to work?

Where is the DHCP server in your network?

Where is the router?

Do you have IP helper-addresses configured?

[YenLin]

i think there isn't any dhcp config error, as I said, edge switch configed as ip add dhcp then they can get an ip address of that scope, so the ip helper-address are configed on routers as well.
2 clues
1.Even the switch port config as untag vlan 2020 then the client should get an ip range with 10.128.128.x/24, but the pc showed it's ip add 10.128.144.x/24 which is belong to vlan 2040 and can't ping to the default gateway.
2.If I configed static ip address then it works perfect.

[Vince_Whirlwind]

Can you show us the

 -interface config for the VLAN interfaces on your router for VLAN 2020.

 -interface config for the VLAN interfaces on your router for VLAN 2040.

 -interface config for the physical interface your PC is patched to.

[YenLin]

As requested.

vlan 2020
   name "CORPLAN"
   tagged F1,H1,H4-H8,H10,H12-H14,H16,H18-H24,L1-L3,L5-L6,L8-L9,L11,L15-L18,L23-L24,Trk4-Trk5
   ip address 10.128.128.1 255.255.255.0
   ip helper-address 172.20.1.65
   ip helper-address 172.20.1.66
   ip ospf 10.128.128.1 area 10.128.0.0
   ipv6 enable
   exit

vlan 2040
   name "MANAGEMENT"
   tagged F1,H1,H4-H8,H10,H12-H14,H16,H18-H24,L1-L3,L5-L6,L8-L9,L11,L15-L18,L23-L24,Trk4-Trk5
   ip address 10.128.144.1 255.255.255.0
   ip proxy-arp
   ip helper-address 172.20.1.65
   ip helper-address 172.20.1.66
   ip ospf 10.128.144.1 area 10.128.0.0
   ipv6 enable
   exit

The physical patched port already on attached file 2520-8G.

Post as below as well.

vlan 2020
   name "CORPLAN"
   untagged 2
   tagged 10
   no ip address
   exit

There is a switch between them, but I have been using my NB to connect to that switch as well and got same result.

[Vince_Whirlwind]

First thing I would check is this:

 - What port is your DHCP server on, exactly? What VLAN is "untagged" and VLANs are present as "tagged" (if any - should be none) on that port?

Secondly, I would trace the path between client and server :

Please specify what ports on each switch are involved in the connection between them - each access port and each uplink port in between, plus the VLAN config for each of those ports, maybe just do a "show run int xx" for each one.

[paulgear]

I don't think the port the DHCP server is on is relevant, because the L3 switch is doing forwarding to it with 'ip helper'. I'd say it's just selecting the wrong scope.

YenLin, what is the setting of 'dhcp-relay option 82' on your routing switch? Assuming it is the only relay on your network (i.e. the DHCP client is only one L3 hop away from your DHCP server) then you probably should set this to 'replace' if it's not already set. See the multicast & routing guide for your switch for more info on this.

[YenLin]

Hi Vince_whirlwind, our dc1 is on the core port and show config as below
interface E7
   name "hitechonesql(172.20.90.36)/hixenapp1(172.20.90.2)/hifrontier"
   no power-over-ethernet
   untagged vlan 1
   loop-protect
   exit
The connection DC1-E7 <-> Core-L13 <-> ITservices-52
Core L13 config showed as below:
interface L13
   name "Backup_ITServices"
   tagged vlan 7,10,15-17,19-22,25,30,121-122,150,400,700,1000,2001,2020,2040,2051-2053,2060
   untagged vlan 1
   exit

------------------------------------------------------
Then the ITservices-port 52 config:
interface 52
   name "LINK_TO_Core-L15"
   tagged vlan 15-16,19-22,122,2001,2020,2040,2052-2053,2060
   untagged vlan 1
   lldp enable-notification
   exit
=======================================================
End up with IT services-port 45
interface 45
   tagged vlan 2060
   untagged vlan 2020
   lldp enable-notification
   loop-protect
   exit

[YenLin]

Hi paulgear, we are doing ip migration and previously we only got 1 enable L3 routing.

Now, we have enabled 6 * 5400 to enable L3 routing and using OSPF

Then, this is the problem we have for new infractructure.

New Created vlans can't get dhcp ip address assign for clients but can get an ip address on switches.

Did you mean we have to use dhcp option 82 in our environment?

Thanks for your answer.

[YenLin]

Hi everyone,

Our DHCP problem is solved, but I even don't know why it solved.

The thing that I have been done just only disable MSM controller's Mobility function.

There maybe other thing that we have been made.

But, there isn't any problem with dhcp assign ip to client anymore.