Problems with DHCP - windows Vista

[rasoftware]

I'm having trouble getting my Vista clients to accept DHCP from the router.  XP are working fine.

I have attached the config - I suspect I may need a newer version or the IOS.

[Jigar Dave]

Hello,

The problem occurs with DHCP flag in Vista.

To resolve this issue yourself, disable the DHCP  BROADCAST flag in Windows Vista. To do this, follow these steps:

click on start - run - type cmd - type regedit
locate
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters\Interfaces\{GUID}
create new -  click DWORD (32 bit) value
in box - type DhcpConnEnableBcastFlagToggle - press enter
right click on DhcpConnEnableBcastFlagToggle - modify - value data box - type  1 - click ok
close regedit

by doing this Windows Vista will first try to obtain an IP address by using the BROADCAST flag in DHCP Discover packets. If that fails, it will try to obtain an IP address without using the BROADCAST flag in DHCP Discover packets.

HTH

Jigar Dave

[rasoftware]

Many thanks for your response.

This is a managed network so not that easy to change all the PC's - is there an updated version of the IOS or command I can enter to negate this on the switch?

Thanks

Rob

[Jigar Dave · Accepted solution]

Hi,

Before implementing vista on this environment; have you not checked this thing ?

I will check for router commands, please provide me your router information. router to L3 switch connectivity and L3 switch to LAN connectivity.

Thanks

Jigar

[rasoftware]

It a system I have inherited! Routers are Cisco 1800

[rasoftware]

Hi,

I tried MS KB 928233 - and this doesn't resolve it.  Also this affects Windows 7 which works differently.

I am at a complete loss as to why they won't received DHCP addresses from the switch.  XP is working fine.

[rasoftware]

I also see this from the Vista client and response from switch

1w6d: DHCPD: Sending DHCPOFFER to client 0100.1d92.0650.5e (192.168.200.172).
1w6d: DHCPD: creating ARP entry (192.168.200.172, 001d.9206.505e).
1w6d: DHCPD: unicasting BOOTREPLY to client 001d.9206.505e (192.168.200.172).
1w6d: DHCPD: DHCPREQUEST received from client 0100.1d92.0650.5e.
1w6d: DHCPD: Sending DHCPACK to client 0100.1d92.0650.5e (192.168.200.172).
1w6d: DHCPD: creating ARP entry (192.168.200.172, 001d.9206.505e).
1w6d: DHCPD: unicasting BOOTREPLY to client 001d.9206.505e (192.168.200.172).
1w6d: DHCPD: DHCPDISCOVER received from client 0100.1d92.0650.5e on interface Vlan200.

[rasoftware]

I managed to resolve this - nothing to do with DHCP broadcasts.

I removed the subnet mask from the default gateway and it works fine on Vista and 7 now.

[mwandu]

rasoftware,

please share what you mean exactly that 'you removed subnet mask from the gateway'

thank you in advance.

[killafunkinmofo]

Wow that was a nice find.

Now i know why it sometimes worked with me and sometimes didn't after reconfiging my router

ip dhcp pool pool2
   network 10.2.0.0 255.255.255.0
   dns-server 10.2.0.0 255.255.255.0
   default-router 10.2.0.1 255.255.255.0 <-------------- I'm pretty sure he is refering to that subnet mask.

ip dhcp pool pool2
   network 10.2.0.0 255.255.255.0
   dns-server 10.2.0.0 255.255.255.0
   default-router 10.2.0.1

BTW MS is POS

[rasoftware]

That's the one.

For some reason XP is ok with this in the DHCP response but rightly Vista/7 rejects this.

It was a system I inherited so not a config I would normally do.

Hope this helps anyone with similar issues.

The DHCP broadcast is resolved in 12.2 I believe