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    IP Alias vs Proxy ARP - When to use what & why ?

    Scheduled Pinned Locked Moved HA/CARP/VIPs
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    • JeGrJ
      JeGr LAYER 8 Moderator
      last edited by

      Besides having a (V)IP, that isn't really located on the device but further down/up the wire, I haven't seen much use in nowadays setups with ProxyARP IPs but that case is a really nice touch for many setups that formerly used some other "darkmagic"(tm) Software that bridged VPN into their network or that like to use special inbound/outbound ACLs for a specific IP group/network. :)

      Don't forget to upvote šŸ‘ those who kindly offered their time and brainpower to help you!

      If you're interested, I'm available to discuss details of German-speaking paid support (for companies) if needed.

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      • bingo600B
        bingo600 @JeGr
        last edited by

        @JeGr said in IP Alias vs Proxy ARP - When to use what & why ?:

        How about checking the comparison table? ;)

        https://docs.netgate.com/pfsense/en/latest/firewall/virtual-ip-address-comparison.html

        Also to jump in what you can (only) do with Proxy ARP addresses:

        ..
        ..
        ..

        Cheers
        \jens

        Yddrff that was "Sneaky" šŸ‘
        Where did KISS go šŸ™„

        Excellent example , and "I would never have thought of ....."

        But nice to know (bookmarked)

        Thanx Jens

        /Bingo
        Who was not "Sneaky" , and had to permit my Lan adm AND OVPN RoadWarrior adm network's on all the remote sites (for TFW mgmt access)

        If you find my answer useful - Please give the post a šŸ‘ - "thumbs up"

        pfSense+ 23.05.1 (ZFS)

        QOTOM-Q355G4 Quad Lan.
        CPUĀ  : Core i5 5250U, Ram : 8GB Kingston DDR3LV 1600
        LANĀ  : 4 x Intel 211, DiskĀ  : 240G SAMSUNG MZ7L3240HCHQ SSD

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        • JeGrJ
          JeGr LAYER 8 Moderator
          last edited by

          For what it's worth: IMHO best way is to do it with separate subnets and clean routing, so perhaps you weren't sneaky but did a clean setup as it should be :D

          Don't forget to upvote šŸ‘ those who kindly offered their time and brainpower to help you!

          If you're interested, I'm available to discuss details of German-speaking paid support (for companies) if needed.

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          • bingo600B
            bingo600 @JeGr
            last edited by

            @JeGr said in IP Alias vs Proxy ARP - When to use what & why ?:

            For what it's worth: IMHO best way is to do it with separate subnets and clean routing, so perhaps you weren't sneaky but did a clean setup as it should be :D

            Agreed

            But if you have no control over the "remote box" (CPE) , and want to be able to access it from a new dial-in scope.
            The sneaky is nice to have in the "darkmagic"(tm) (love that word) toolbox

            /Bingo

            If you find my answer useful - Please give the post a šŸ‘ - "thumbs up"

            pfSense+ 23.05.1 (ZFS)

            QOTOM-Q355G4 Quad Lan.
            CPUĀ  : Core i5 5250U, Ram : 8GB Kingston DDR3LV 1600
            LANĀ  : 4 x Intel 211, DiskĀ  : 240G SAMSUNG MZ7L3240HCHQ SSD

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            • JeGrJ
              JeGr LAYER 8 Moderator
              last edited by

              @bingo600 said in IP Alias vs Proxy ARP - When to use what & why ?:

              The sneaky is nice to have in the "darkmagic"(tm) (love that word) toolbox

              Absolutely. Those nice little hacks you can/could do are the bread&butter of your toolset and what makes my customers and clients happy ;)

              Did I mention there's also such a hidden gem in outbound NATting in relation with properly routed public subnets? 😁

              Don't forget to upvote šŸ‘ those who kindly offered their time and brainpower to help you!

              If you're interested, I'm available to discuss details of German-speaking paid support (for companies) if needed.

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              • bingo600B
                bingo600 @JeGr
                last edited by

                @JeGr said in IP Alias vs Proxy ARP - When to use what & why ?:

                Did I mention there's also such a hidden gem in outbound NATting in relation with properly routed public subnets? 😁

                More...More...

                /Bingo

                If you find my answer useful - Please give the post a šŸ‘ - "thumbs up"

                pfSense+ 23.05.1 (ZFS)

                QOTOM-Q355G4 Quad Lan.
                CPUĀ  : Core i5 5250U, Ram : 8GB Kingston DDR3LV 1600
                LANĀ  : 4 x Intel 211, DiskĀ  : 240G SAMSUNG MZ7L3240HCHQ SSD

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                • JeGrJ
                  JeGr LAYER 8 Moderator
                  last edited by

                  Just a quicky:

                  • You have a public WAN IP
                  • You have another subnet routed to said WAN IP (let's say a /30 as the ISPs are greedy as f*** these days)
                  • So you get 2 additional usable IPs out of that. It's a /30 right?

                  Nope ;) You can use those 2 IPs for services/servers down the wire, for sure. Even create that nice little /30 on another interface and setup a server to have a real public IP. Or you could BiNAT both IPs to 2 servers. Right.

                  But you can also "exploit", that your ISP is routing that /30 to you. Completely. To do what you want. So how about setting up the network or the broadcast IP as an "IP Alias" type IP on your pfSense and use it as NAT outgoing IP for your VLAN1 network? And the other one for your VLAN2 network? That leaves your pfSense WAN IP AND those other 2 real IPs from the /30 to your handling as you please without using/burning one of them with outgoing traffic from your NAT.

                  Just a little tidbit. You can use the network/broadcast IP that way ONLY, because outbound NAT etc. aren't actually services, that listen on a specific interface/IP but just "rewrite" IP informations. And as you get that /30 routed to you from the ISP, returning traffic even to the netmask/broadcast IP is normally coming back without a hitch and retranslated to the origin via PFs filter engine. :) But where it works and where not needs a bit of fiddling or searching around.

                  Saves up on sparse IPs ;)

                  Don't forget to upvote šŸ‘ those who kindly offered their time and brainpower to help you!

                  If you're interested, I'm available to discuss details of German-speaking paid support (for companies) if needed.

                  bingo600B 1 Reply Last reply Reply Quote 1
                  • bingo600B
                    bingo600 @JeGr
                    last edited by bingo600

                    @JeGr
                    Hmm .. Didn't ie. Cisco add "drop broadcast" traffic , default to their IF's ?
                    Must find an ISP that runs Juniper 😊

                    I was lucky ... Have a /27 at work

                    Edit: BiNAT ??

                    /Bingo

                    If you find my answer useful - Please give the post a šŸ‘ - "thumbs up"

                    pfSense+ 23.05.1 (ZFS)

                    QOTOM-Q355G4 Quad Lan.
                    CPUĀ  : Core i5 5250U, Ram : 8GB Kingston DDR3LV 1600
                    LANĀ  : 4 x Intel 211, DiskĀ  : 240G SAMSUNG MZ7L3240HCHQ SSD

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                    • JeGrJ
                      JeGr LAYER 8 Moderator
                      last edited by

                      That shouldn't interfere with a routed subnet as that is "customers property" normally. I'd be pissed if they filtered traffic of my IP space before it gets to me :)

                      Edit: BiNAT ??

                      1:1 NAT is also called BiNAT (as it's mapping in- and outbound).

                      Don't forget to upvote šŸ‘ those who kindly offered their time and brainpower to help you!

                      If you're interested, I'm available to discuss details of German-speaking paid support (for companies) if needed.

                      bingo600B 1 Reply Last reply Reply Quote 0
                      • bingo600B
                        bingo600 @JeGr
                        last edited by bingo600

                        @JeGr
                        Ahh so the new /30 is not given as a "Link-net" , just a "range"
                        Nice "abuse"

                        Soon you'll prob. get a /31 as link-net
                        https://tools.ietf.org/html/rfc3021

                        If i refer to this post .. Doubling your Public IP range
                        Do you think i could argue that i should have a /26 😊 😊

                        /Bingo

                        If you find my answer useful - Please give the post a šŸ‘ - "thumbs up"

                        pfSense+ 23.05.1 (ZFS)

                        QOTOM-Q355G4 Quad Lan.
                        CPUĀ  : Core i5 5250U, Ram : 8GB Kingston DDR3LV 1600
                        LANĀ  : 4 x Intel 211, DiskĀ  : 240G SAMSUNG MZ7L3240HCHQ SSD

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                        • JeGrJ
                          JeGr LAYER 8 Moderator
                          last edited by

                          @bingo600 said in IP Alias vs Proxy ARP - When to use what & why ?:

                          Do you think i could argue that i should have a /26

                          šŸ˜‚

                          Don't forget to upvote šŸ‘ those who kindly offered their time and brainpower to help you!

                          If you're interested, I'm available to discuss details of German-speaking paid support (for companies) if needed.

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                          • bingo600B
                            bingo600
                            last edited by

                            @JeGr & @JKnott
                            Thank you for taking your time to enlighten me.
                            I just love to get more tools in my "darkmagic"(tm) toolbox

                            Thanx guyzz

                            /Bingo

                            If you find my answer useful - Please give the post a šŸ‘ - "thumbs up"

                            pfSense+ 23.05.1 (ZFS)

                            QOTOM-Q355G4 Quad Lan.
                            CPUĀ  : Core i5 5250U, Ram : 8GB Kingston DDR3LV 1600
                            LANĀ  : 4 x Intel 211, DiskĀ  : 240G SAMSUNG MZ7L3240HCHQ SSD

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                            • W
                              wesleywillis
                              last edited by

                              Hello, realize this is an older thread but looking to gain insight on the subject as well.

                              I have a /26 public IP block, and currently use ProxyARP and 1:1 NAT to route traffic to Hyper-V VMs/web servers. I'll be adding subnets using VLANs to further isolate some new VMs. Is there any reason I should be using IP Aliases instead, or is ProxyARP fine for this application?

                              Thanks for any enlightenment!

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