DHCP in non default-profile unp vlan

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Favorite
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Posts: 4
Joined: 31 Jan 2018 00:54

DHCP in non default-profile unp vlan

Post by Favorite » 19 Jul 2019 04:28

Hi,

we're facing a problem with DHCP-process on unp brigde port types.
The clients do only get a valid DHCP-Adress if either the vlan is set as default or if the default unp profile matches the vlan it should a dhcp lease from.

Here you can find an example of our configuration
-> Edge Switch 6860 with vlan-10 and vlan-20 (vlan 10 as unp default)
unp classification ip-address 192.168.10.0 mask 255.255.255.0 profile2 "vlan-10"
unp classification ip-address 192.168.20.0 mask 255.255.255.0 profile2 "vlan-20"
unp profile "vlan-10" map vlan 10
unp profile "vlan-20" map vlan 20
unp port-template TEST_1 redirect-port-bounce direction both default-profile "vlan-10" classification admin-state enable
unp port-template TEST_1 force-l3-learning
unp port 1/1/1 port-type bridge
unp port 1/1/1 port-template TEMPLATE_1

-> Core Switch OS6900
ip interface "vlan-10" address 192.168.10.1 mask 255.255.255.0 vlan 10
ip interface "vlan-20" address 192.168.20.1 mask 255.255.255.0 vlan 10
ip helper vlan 10 address 192.168.100.5
ip helper vlan 20 address 192.168.100.5


If I provide a DHCP-reservation on our Microsoft DHCP server in the 192.168.10.0/24 scope the client get's the reservation without problems.
If I provide the reservation in the 192.168.20.0/24 scope the server receives the DHCP-Discover, but doesn't answer. It works without problems if I put the client access port to vlan 20 as default.

Do you have any idea to get it working with different vlans but with unp?
If you need additional information, please let me know.

Thanks a lot for your time!
Bests,
Favorite
Last edited by Favorite on 22 Jul 2019 02:14, edited 1 time in total.
OS6900: 8.4.1.141.R03 GA
OS6860: 8.4.1.141.R03 GA

silvio
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Re: DHCP in non default-profile unp vlan

Post by silvio » 21 Jul 2019 04:30

I miss a classification rule. How do the switch know about clients in vlan 10 or 20? Different client-Ip-adress because of reservation?
I assume that a static configured IP (at the client) in net 20 doesn't work too.
regards
Silvio

Favorite
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Posts: 4
Joined: 31 Jan 2018 00:54

Re: DHCP in non default-profile unp vlan

Post by Favorite » 22 Jul 2019 02:28

Dear Sivlio,
thanks for your reply. I forgot to post the classification rule but it exists. I edited my post.
If I use the IP-Address static, it does work without problems.
If I put the Client port to the specific vlan, it also works without problems.
The problem appears if the unp puts the client to the default profile (vlan-10). The core should bring it to the DHCP-Server via ip helper which should provide an IP-adress of the vlan-20 scope. -> This is what doesn't work
If I change static IP from vlan-10 to vlan-20 IP the unp profile changes within seconds but I'm not sure how it should behave in combination with ip helper.
Best regards,
Favorite
OS6900: 8.4.1.141.R03 GA
OS6860: 8.4.1.141.R03 GA

brnfnd
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Posts: 2
Joined: 07 Feb 2019 04:00

Re: DHCP in non default-profile unp vlan

Post by brnfnd » 07 Nov 2019 13:20

Hi Silvio,

we were able to fix the problem. After looking in the DHCP Server logs (in the event viewer, not in plain text files which are also exist), the error was clear: the dhcp server determines the subnet for distribution based on the GIADDR (the ip address of the relay agent), and complains that there are no free addresses in that scope, which is correct as we don't have free addresses there (excluded all addresses), only static leases. Thats why there are no Dhcp Offer in Wireshark, only Discover, as he drop the discover packages

The solution for this problem is called "Superscope".
After creating a superscope and putting all wanted scopes in, it works like a charm now :-)

So for future reference: If you want to serve multiple vlans via DHCP, but also has a default vlan, you need to create a superscope and place all your scopes in it.
In the ISC DHCP Server, a superscope can be created via
8<---
shared-network <SCOPENAME> {
subnet xxx {
}
}
8<---

In Microsoft DHCP via GUI or Powershell

Best Regards
brnfnd
OS6900: 8.4.1.141.R03 GA
OS6860: 8.4.1.141.R03 GA

silvio
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Posts: 1385
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Location: Germany

Re: DHCP in non default-profile unp vlan

Post by silvio » 08 Nov 2019 10:54

Hi jns,
thanks for this good news and clarification about the source of your issues.
have a nice weekend.
Silvio

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