Problem with Vlan DHCP, wrong Subnet IP address

120 pts.
Tags:
DHCP
L3 Switches
Subnets
VLAN
Hi, I have a problem with my Vlan, the problem is; I have got a Win2k Server with DHCP configured, 1x Superscope, with 3 scopes underneath it, subnets 192.168.2.0 (range 100-254), 192.168.20.0 (range 100-254), and 192.168.30.0 (range 100-254). When I manually enter the to the port according Ip address on my client PC, it all works a treat, but when I request a DHCP address, it just gives me a 192.168.2.0 IP, and I cannot access any resources. Here is my config; !Current Configuration: !System Description "Dell 24 Port Gigabit Ethernet, 2.0.0.12, VxWorks5.5.1" !System Software Version 2.0.0.12 ! configure vlan database vlan 10,20,30 vlan association subnet 192.168.2.0 255.255.255.0 10 vlan association subnet 192.168.20.0 255.255.255.0 20 vlan association subnet 192.168.30.0 255.255.255.0 30 exit stack member 1 1 exit switch 1 priority 1 ip address 192.168.1.1 255.255.255.0 ip default-gateway 192.168.2.201 ip routing ip route 0.0.0.0 0.0.0.0 192.168.2.201 bootpdhcprelay enable bootpdhcprelay maxhopcount 16 bootpdhcprelay serverip 192.168.2.10 bootpdhcprelay cidridoptmode ip helper-address 192.168.2.1 192.168.2.10 37 ip helper-address 192.168.2.1 192.168.2.10 49 ip helper-address 192.168.2.1 192.168.2.10 137 ip helper-address 192.168.2.1 192.168.2.10 138 ip helper-address 192.168.20.1 192.168.2.10 37 ip helper-address 192.168.20.1 192.168.2.10 49 ip helper-address 192.168.20.1 192.168.2.10 137 ip helper-address 192.168.20.1 192.168.2.10 138 ip helper-address 192.168.30.1 192.168.2.10 37 ip helper-address 192.168.30.1 192.168.2.10 49 ip helper-address 192.168.30.1 192.168.2.10 137 ip helper-address 192.168.30.1 192.168.2.10 138 interface vlan 10 name "Servers" routing ip address 192.168.2.1 255.255.255.0 ip netdirbcast exit interface vlan 20 name "Sales" routing ip address 192.168.20.1 255.255.255.0 ip netdirbcast exit interface vlan 30 name "Accounts" routing ip address 192.168.30.1 255.255.255.0 ip netdirbcast exit username "michi" password 4f70cfb1451a1b0ce0b872421bee6c1c level 15 encrypted ! interface ethernet 1/g1 switchport mode general switchport general pvid 10 no switchport general acceptable-frame-type tagged-only switchport general allowed vlan add 10,20,30 exit ! interface ethernet 1/g3 switchport mode general switchport general pvid 10 no switchport general acceptable-frame-type tagged-only switchport general allowed vlan add 10,20,30 exit ! interface ethernet 1/g4 switchport mode general switchport general pvid 20 no switchport general acceptable-frame-type tagged-only switchport general allowed vlan add 20 exit ! interface ethernet 1/g5 switchport mode general switchport general pvid 10 no switchport general acceptable-frame-type tagged-only switchport general allowed vlan add 10,20,30 exit ! interface ethernet 1/g8 switchport mode general switchport general pvid 30 no switchport general acceptable-frame-type tagged-only switchport general allowed vlan add 30 exit ! interface ethernet 1/g24 switchport mode general switchport general pvid 10 no switchport general acceptable-frame-type tagged-only switchport general allowed vlan add 10,20,30 exit exit Any help or comments are welcome. Thank you Micahel

Answer Wiki

Thanks. We'll let you know when a new response is added.

Unfortunately for us, this is working as designed, designed like #&!%.

Superscopes override individual scopes. You will need to create individual scopes for each VLAN subnet. I had the same problem. I wanted to use superscopes to try and make management easier but it creates the problem that you described. Once I created individual scopes for each VLAN subnet, my problems went away.

Take a look at the following MS KB articles
<a href=”http://support.microsoft.com/kb/169290/en-us”>169290</a> – DHCP reservations do not get assigned from a superscope – notice the line: <b>This is happening because a DHCP server normally hands out addresses from a superscope starting with the first scope. After that scope is full, the server starts handing out addresses from the second scope, third scope, and so on. </b>

<a href=”http://support.microsoft.com/kb/186341/en-us”>186341</a> – Superscoping vs supernetting

I had been advise that I also need to add option 82 (DHCP-Relay support) to my DHCP server in predifined options: http://slaptijack.com/networking/what-is-dhcp-option-82/

To enable DHCP-relay support:
Using DHCP Server Management console (dhcpmgmt.msc) -> -> Right Click -> Set Predefined Options…, you can add option 82 as a customized option for DHCP Server

Does anyone know what to select?

Thanks

Hello thanks for all your inputs;
I have just gone to my DHCP server which is connected to port 1/g1 Vlan10 and disabled the scope for 192.168.2.0 subnet, as this is mainly used for servers with fixed IP addresses and isn’t really necessary, now when I plug my client PC into port 1/g4 I receive a 192.168.20.0 address and when I plug it into port 1/g8 I receive a 192.168.30.0 address. Its working a treat. :)
One last thing, I cannot access the internet once I received a 192.168.20.0 or 192.168.30.0 IP address can you please tell me where I have gone wrong, must be something to do with my routes.

Thank you

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  • Labnuke99
    Yes, it sounds like something is wrong with the routes. You will need to ensure that your router knows how to get to each VLAN you have defined. If you are using the switch as the gateway to these VLANs, then you should put a route on the router to the switch for those VLANs. I would also take a look to see if EIGRP or some other routing update protocol can be used on the switch to automatically publish these routes to the router for you.
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  • Deweywhite
    Sorry, I have a situation where the a few PC will not pull the DHCP, and all hardware and configurations seem correct. Ant Ideals
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  • Labnuke99
    Deweywhite - please go ahead and post a new question here and let us know what you have tried to do to resolve the DHCP lease issue. Some things to look at: VLAN switch port membership - including DHCP helper statements DHCP scope exhaustion - is the scope big enough? Is something quenching the DHCP request broadcast? Use Wireshark to listen for traffic to/from the problem client(s) client may have static IP address assigned - modify client config I look forward to seeing your question posted.
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  • Sixball
    I noticed you have the Line "ip route 0.0.0.0 0.0.0.0 192.168.2.201", bt your last comment said you removed the path to the 192.168.2.x VLAN - could be a good palce to look as it seems you removed the devices knowledge of the route you're shoving traffic to...
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