SRX

Hi

I have a problem when using an SRX as a DHCP-relay. The problem is that when the SRX sends a unicast message to the DHCP-server it does not use the interface it receives the request on as source. This is, as i understand it, a "correct" behaviour, but it couses some problems for me.

Setup is simple. The SRX receives the request on the LAN-interface, which should be sent to the DHCP over the WAN. It sends a request using the WAN-ip as source. My problem is that the link net on the WAN is not routed in the DHCP, so the response wont find its way back.

There is a configuration statement that should override this behaviour, but it does not seem supported in the SRX.

forwarding-options {
    ##
    ## Warning: configuration block ignored: unsupported platform (srx100b)
    ##
    ##
    dhcp-relay {
        overrides {
            replace-ip-source-with giaddr;
        }
    }
}

Does anyone know a way to solve this other than routing the WAN-ip on the DHCP?

regards,

Karl

Hi Karl,

I see some configuration missing in your DHCP relay configuration

set forwarding-options helpers bootp server 192.18.24.38 ----> This ip address is the Ip of the DHCP server. 

If the route is via the Wan link it will forward the packet through that path.

set forwarding-options helpers bootp vpn --> Use this config for using Lan ip for sending the DHCP uni-cast request.

set forwarding-options helpers bootp interface fe-0/0/7.0 --> This is the interface that receives the DHCP discover message on the srx.

Hope this helps.

Regards,

Visitor

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Thank you.

The "vpn" setting solved our issue.

/Karl