DHCP WAN Subnet Mask

  • I have my internet connection bridged from a modem to the WAN interface of my pfSense box, but I am having trouble with connectivity at the moment.

    I have been taking the time to learn more about the setup and have a (hopefully) quick question for you guys.

    When looking at my WAN interface in the 'DHCP Client Configuration' section there is an option for an 'alias IPv4 address' and subnet mask as pictured in attached.

    I don't think I need an alias set in here but can anyone tell me if setting the subnet mask makes a difference if the WAN connection is DHCP,? My thinking is that the correct subnet mask would be obtained by the DHCP server? Do I need to match this setting to the one obtained by DHCP?

    ![Screen Shot 2016-08-20 at 21.54.34.png](/public/imported_attachments/1/Screen Shot 2016-08-20 at 21.54.34.png)
    ![Screen Shot 2016-08-20 at 21.54.34.png_thumb](/public/imported_attachments/1/Screen Shot 2016-08-20 at 21.54.34.png_thumb)

  • LAYER 8 Global Moderator

    I highly doubt you have use of that - that is for if your dhcp client ie your wan doesn't get an answer from your dhcp server.. I would use that address, yes then if you used it your mask would be what you set there.  It makes no difference at all what that mask is unless your not getting an IP from your dhcp server and using your alias IP, etc.

  • Understood. Thanks for the explanation. DHCP is working fine for IPv4, struggling with IPv6 though. Either way I think I will steer clear of this setting!

  • LAYER 8 Global Moderator

    it has nothing to do with ipv6 either.. Do have a ipv6 thread going over that issue?  If so will take a look.  To be honest maybe my isp has just soured my grapes, etc.  But I just feel that many of the isp just not ready for primetime ipv6 deployment.  If want a /48 give me a /48 - for gosh sake a /56 at min via pd so I can have multiple segments inside my network.. Sorry but 1 /64 is just not enough..

    And that /48 or /56 I get shouldn't freaking change at the drop of hat..  I should have that and always have that same pd..

    If you want stable ipv6 where you might have get the pd you requested you might not, if you get one its prob different then the one you had yesterday, etc.

    I just run a tunnel from HE..  I know exactly what /48 I have.. Doesn't change - always up, speed is good, etc..

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