PfSense 2.1-RELEASE not recognizing DHCP with public IP from DSL modem



  • I have a new installation which for reasons beyond my control needs to sit behind a DSL modem/router device temporarily.  This is not a long-term configuration, but I'd still rather have as little NAT as possible involved so I'm attempting to use the modem's "Public IP Passthrough" function.

    With no special configuration, the pfSense box gets DHCP from the modem with a private address and all is well.  As soon as I enable the public address passthrough however, things get nasty and pfSense no longer seems interested in accepting the lease.  I can do the same to my laptop (OS X 10.8) and it works fine, I get the public address via DHCP and all works well, but the pfSense DHCP client doesn't seem to like it.

    Where this becomes a big problem is that this seems to also prevent the pfSense box from booting properly.  It reaches "configuring WAN interface" and just sits there doing nothing rather than timing out in a reasonable period and moving on.  I've seen references to similar issues in 1.2.x where apparently there's a 20 minute timeout, but that's absolutely absurd.  If there's no response after a minute, assume DHCP is hosed up and move on.

    Here's a packet capture of the DHCP exchange.  It looks like pfSense is asking for more information or to confirm the DHCP lease and the DSL modem isn't responding, but it was already provided with enough information to get a useful internet connection going so regardless of a further lack of response it should at least move ahead with that.

    http://cloudshark.org/captures/cf0f04fce856

    And yes I know the 100.100.100.x addressing on the DSL modem is stupid, not my doing and it's going away soon, just I'm stuck working behind that device for now.



  • sounds more like DNS issue but as a longshot you might try setting the offending interface from "auto-negotiate" to "no preference".


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