IP-Helper

[hunnetvl01]

Hi All,

I have a dhcp server on w2k3 and one scope for one LAN .

I want to have another scope on the same dhcp server for a 2nd Vlan and I did the IP helper and ip broadcast on the 2nd Vlan interface but it is not working.

No PC gets IP in the second scope.

Thaks,

Vlad

[scottmac]

Please post your router config.

Thanks

Scott

[John Blakley]

Make sure that your vlan 2 SVI shows up and that the ports that the PCs are attached two are access ports of vlan 2. Otherwise, if this is the case, please do as Scott suggested and post the switch or router config.

HTH,

John

[hunnetvl01]

I ve done all these ...and routing is also enabled.

No idea tho' what s wrong

Thx,

Vlad

[hunnetvl01]

Scott ,

this is what I ve configured

This is a L3 Switch 4507.

interface Vlan7

ip address 172.20.19.1 255.255.255.0

no ip unreachables

no ip proxy-arp

load-interval 30

end

#sh run int vlan 60

Building configuration...

interface Vlan60

ip address 172.16.6.254 255.255.255.0

ip helper-address 172.51.19.254

ip directed-broadcast

end

The DHCP server is in Vlan 7 and has a scope for Vlan 60.

There is no ACL anywhere that could block any tcp or udp traffic.

Thanks,

Vlad

[hunnetvl01]

sorry the ip helper is 172.20.19.254 not as I copy pasted it.

[John Blakley]

Make sure you have ip routing enabled. Can you ping VLAN 60 from a system in Vlan 7, like the DHCP server?

Oh, and is your scope enabled on the server?

HTH,

John

[hunnetvl01]

I can ping the SVI in 60 from the DHCP in 7 and scope is also active.

thx

Vlad

[Jon Marshall]

Vlad

Can you post

"sh ip int brief"

"sh ip route"

sh int ?? where ?? is the interface that you have a PC plugged into on vlan 60.

Jon

[hunnetvl01]

Jon,

I assume this is what u are interested in:

172.16.0.0/16 is variably subnetted

172.16.6.0/24 is directly connected, Vlan60

Vlan60 172.16.6.254 YES manual up up

interface GigabitEthernet3/6

switchport access vlan 60

switchport mode access

switchport nonegotiate

load-interval 30

no snmp trap link-status

spanning-tree portfast

Thanks,

Vlad

[sachinraja]

Hello vlad

not sure why you need "ip directed broadcast" on vlan 60 interface ! ip helper actually converts your dhcp broadcasts to a unicast message.. in any case, run a sniffer on the PC, and see what happens.. See if you get any updates back from the dhcp server.. do you see any error logs on the server ? make sure you specify a dhcp exclude address for 172.16.6.254 , which is the vlan 60 SVI interface !

Raj

[hunnetvl01]

Hello Raj,

I know the ip-helper converts the broadcast to unicast , but I could not get it to work so I tried.

Anyway , if I hardcode an IP address on a PC in that Vlan I can ping the DHCP and viceversa.

I will wireshark it and let you know.

Thanks,

Vlad

[Richard Burts]

Vlad

If you take a PC in the subnet that is not getting addresses from the DHCP server and you hard code an IP address of that subnet on the PC, can the PC then ping the DHCP server?

HTH

Rick

[hunnetvl01]

Rick,

The server and the PC can ping one another.

I have wireshark it and I see the request from the PC but no arp from the DHCp server.

Anyway,

I dont know if I mentioned it , but on the same server I have another DHCP scope in vlan 7.

Thx,

Vlad

[Ramprasad Pr]

Vlad,

Same configuration made it in my lab its working fine . check changes what i made in configuration.

interface Vlan7

ip address 172.20.19.1 255.255.255.0

end

interface Vlan60

ip address 172.16.6.254 255.255.255.0

ip helper-address 172.20.19.254

no ip directed-broadcast

end

interface GigabitEthernet3/6

switchport access vlan 60

switchport mode access

sw host

Regards

Ram