Client uses ISP DNS under ASA5520

[Jackong]

kindly assist me rgarding this issue i have my router connected to ISP then my router directly connected to my ASA5520....i use also ASA5520 as my DHCP Server and i was wondering with the DHCP Server function of ASA 5520 because if i use the ASA 5520 LAN ip ...all workstation will not be able to browse anything from the internet unless i use my ISP DNS IPwhich they gave me

[Jouni Forss · Accepted solution]

Hi,

I am not sure if I understood your question correctly.

You ASA uses DHCP on its "outside" perhaps to get IP address and also DNS information from the ISP and you would want to relay this information for the LAN users that use DHCP on the ASAs "inside" interface?

To my understanding that would be configured in this way for example

dhcpd address 10.10.10.100-10.10.10.200 inside

dhcpd auto_config outside

dhcpd enable inside

To my understanding the ASA should be able to now pass the information that it receives with DHCP through the "outside" to also the DHCP clients it provides services for.

- Jouni

[Jackong]

Hi,

my ASA5520 is having Static public IP Address my inside interface is using DHCP for the client and i was wondering that the DHCP needs the ISP DNS for the internet to work

example

Outside:

172.21.6.146/29

inside:

dhcpd address 192.168.0.10-192.168.0.254 inside

dhcpd dns DNS1 DNS2 interface inside

dhcpd domain dechout.com.sa interface inside

dhcpd enable inside

i already change it to this hope it is correct now

[Jouni Forss]

Hi,

That seems correct to me.

I thought you were getting IP information to the ASA from some ISP device and wanted to pass them along with the ASA to the DHCP clients behind ASA.

If thats not the case (as it seems) then you simply configure the DHCP pool on the ASA to use the DNS servers they provided.

There is also option to use some other public DNS servers. I think Google also had DNS servers with IP addresses 8.8.8.8 8.8.4.4 for example

- Jouni