sorry typo its ip helper-address 192.168.1.5 and the ip address of the vlan 1 is 192.168.1.1
Now if add a static ip address e.g 192.168.250.10 to a pc it pings everything on 192.168.1.x.
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Cisco 3750G with secondary IP address in the default VLAN and IP Helper
I have a cisco 3750G and i am running out of IP's in my default VLAN. I have issued a secondary ip in the default vlan add the ip helper command to point out my dhcp.
My config looks like this.
ip routing
ip classless
ip subnet-zero
interface Vlan1
ip address 192.168.1 255.255.255.0
ip address 192.168.250.1 255.255.255.0 secondary
ip helper-address 192.168.100.5
no ip route-cache
I don't know if i have configured correct the dhcp server.
I 've added a second scope with range 192.168.250.2-192.168.250.
dns 192.168.1.10 default gw 192.168.250.1
When my first scope is full i don't see leases from the second scope aka 192.168.250.0.
Instead the clients pc keep searches for dhcp server with no result.
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Answers
Now there are two possibilites in your network
When you ping dhcp server, traffic from PC comes to switch and is forwarded to the Server within the switch as it is performing routing.
OR
The switch forward the traffic to ASA and after filtering ASA forward this traffic to DHCP server and the same happends for the traffic coming back from server to PC.
If the case is first, the helper command entered previously should work.
If teh case is second than there is need to enter following commands on ASA interface which is pointed to PC.
dhcprelay server 'ip addres of your dhcp server' outside
dhcprelay enable inside
dhcprelay setroute inside
You can use tracert command to see what path is being used by ping packet from pc to server.
I am not much into server but you as you have told that your arent using super scope and its sub scopes but you have created two separate scopes for use so it should be fine. To make sure if things are right on the server and to see if you can get it working with some modification in your vlan you can do is to create a separate vlan with the ip addres which you used as secondary on vlan 1 and than use the ip helper address command and see if your pc is able to get the address or not, still keep that helper address command on vlan 1 as well.
You can't make this configuration work. The problem is that until the client PC has an IP address, the only way it can communicate is via broadcast packets. A DHCP request is just such a broadcast packet, which your switch dutifully transmits on all ports, including the port to which your DHCP server is connected. No routing is happening because no IP address is involved -- this is just a broadcast, after all -- and so IP Helper is not used. The DHCP server replies with an address from its primary scope, because no DHCP helper field was populated on the DHCP request by the switch. There is no way around this that I know of.
The right way to expand your addressable space is to increase the subnet mask size, e.g. to 192.168.0.0/23 (255.255.254.0). This will make the IP range 192.168.0.0 through 192.168.1.255. Or you could make it a /22 subnet and get the range 192.168.0.0 through 192.168.3.255, etc. Keep in mind that the subnet must be on a boundary divisible by the subnet size, so you can't start it at 192.168.1, which is why I dropped down to 192.168.0.0.
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by: malikyounasPosted on 2008-05-15 at 05:25:57ID: 21572700
Can you please verify if you are able to ping 192.168.100.5 from your router and also assign a static ip to a pc in 192.168.250.X network with default gateway setting and try to ping 192.168.100.5. It would verify that if your router knows about the 192.168.100.X address where your DHCP server resides.