Is it possible to assign the same static IP for two different MAC addresses?



  • thats a good one, some OS are not able to take it, but if u have lets say wired connection on your table and wifi in your garden, u can disconnect your cable and walk in the garden without an interruption to your skype call and downloads….

    its not a problem with isc dhcp server and in some router/firewall distros like zeroshell...

    and no, its not possible in pfsense



  • @kejianshi:  See clarification as to "why" in my update to the original post.



  • Yep - I see it.

    I never thought to try it.

    I'm pretty sure that all my machines have different MACS for their wireless and ethernet ports.

    Hmmmm - Let me think

    You can set a static IP on the machine, on the laptop its self.  Make sure its outside the DHCP range of the LAN.


  • LAYER 8 Netgate

    Or be a network hooligan and clone the wireless MAC to the wired or vice versa.  Expect shenanigans and troubleshooting woes.


  • LAYER 8 Global Moderator

    Why don't you just use dns to solve this problem - and just make sure the dns record is updated as the "host" machine moves from one network to another, etc.

    I don't understand why wired and wireless would want to be the same IP - you have given some reasons why you think they should.  Don't agree with them to be honest ;)

    For one - wired and wireless networks from security standpoint could be debated even they should even be the same segment.  My wireless is isolated from my wired network, and you will find that many enterprise setups this is also the case.  Wired and Wireless are rarely the same segment other than the smallest of shops or home setups.



  • @johnpoz:

    Why don't you just use dns to solve this problem - and just make sure the dns record is updated as the "host" machine moves from one network to another, etc.

    I don't understand why wired and wireless would want to be the same IP - you have given some reasons why you think they should.  Don't agree with them to be honest ;)

    For one - wired and wireless networks from security standpoint could be debated even they should even be the same segment.  My wireless is isolated from my wired network, and you will find that many enterprise setups this is also the case.  Wired and Wireless are rarely the same segment other than the smallest of shops or home setups.

    totally agree with you on security issues, i try to isolate the wireless network as much as hardware will allow.

    How would you solve the, lets take the skype session, , dying connections when u change ip than? (u go from wired to wireless) Like dying sessions are pain especially when u have bunch of ssh sessions open and they die…

    s



  • Skype comes back up pretty fast - Thats a minor annoyance.

    What are you using the ssh sessions for?



  • skype: minor, but still anoyance…
    ssh...

    well for whats it meant to, beginning with simple remote access, going through x11 export and sometimes some tunneling....

    how is that important for diying of sessions?

    and dont take me wrong, i have dropped same IP for different mac a long while ago, to begin with (i begin with users) because of some os (like window$ whatever version) is not able to take same ip on two ifaces, continuing through migration of dhcp to zeroshell, using pools instead of static definitions of ips for the clients and so and so...  Im just saying that sometimes, specially in small network/home environments it can be useful....



  • I think the cure for you might be to install a headless server that doesn't have to move here and there and everywhere to handle all that and just use your laptop for everything else.


  • LAYER 8 Netgate

    Or just get good wireless and stay on it even when docked.


  • LAYER 8 Global Moderator

    "Or just get good wireless and stay on it even when docked."

    Exactly – here is the thing if your going to be changing networks, you have to expect that a session would die, just reconnect - I don't see an issue here at all.  if I had a ssh session open and I went from wired to wireless - then yeah that session would have to be reopened.  What is the saying you can't fix stupid ;)  Anyone that would think they can maintain sessions while changing their connection type doesn't understand networking ;)

    Even if you move your IP to a different nic - your session like ssh is still going to die..

    So your complaint is your ssh client doesn't reconnect for you?

    As stated to solve your problem don't move your connection - use wireless while docked or undocked, there you go problem solved you never loose your connection ;)



  • Unless your wireless drops…  Which never happens (-;


  • LAYER 8 Netgate

    Which is why I said good wireless, not some $19 tp-link from walmart.



  • "Even if you move your IP to a different nic - your session like ssh is still going to die.."
    ehm, nope..

    "So your complaint is your ssh client doesn't reconnect for you?"
    yeah, but do u have any clue how long it takes for ssh to timeout?

    wireless…. hmm... something like AC than, and even that wont give u gigabit... wire is wire and wireless sux, regardless the price of it..

    And again, dont take me wrong, as i stated earlier... I  just think, that it can be a valid argument... I mean its implementen in ISC.. its a feature, not a liability...

    s


  • LAYER 8 Netgate

    So you want:

    1: the speed of Gig-E when you're wired
    2: the convenience of wireless when you're not
    3: total disregard for the OSI model when you switch between them.

    Got it.



  • I'm convinced personally - I'm switching all my servers to wifi (-;



  • @Derelict:

    So you want:

    1: the speed of Gig-E when you're wired
    2: the convenience of wireless when you're not
    3: total disregard for the OSI model when you switch between them.

    Got it.

    you are totally right…

    but look at this: https://forum.pfsense.org/index.php/topic,36066.msg186013.html#msg186013

    so it still might be possible...

    and does it violate OSI model to have two interfaces with addresses from the same subnet?


  • LAYER 8 Netgate

    No.  It violates the OSI model having two interfaces with the same MAC or two MACs with the same IP.


  • LAYER 8 Netgate

    @stpq:

    and does it violate OSI model to have two interfaces with addresses from the same subnet?

    You have two interfaces:  eth0 at 192.168.1.13 and eth1 at 192.168.1.14

    Your default gateway is 192.168.1.1

    Which interface(s) should be used to send traffic to the gateway?

    It's not against the model, but requires special consideration and per-interface (not just per-subnet) routing rules.


  • LAYER 8 Global Moderator

    @stpq:

    "So your complaint is your ssh client doesn't reconnect for you?"
    yeah, but do u have any clue how long it takes for ssh to timeout?

    Would depend on the settings in ssh server.  What are the settings for ClientAliveInterval, TCPKeepAlive and ClientAliveCountMax?  They could be very short, or very long depending on what the admin of the ssh server set.

    Where is this a ISC dhcp feature - just because you can get something to load and function in the config, does not mean its a SMART thing to do ;)  You can do lots of things that some software will allow - doesn't mean its good practice ;)

    Networking 101, mac's are suppose to be unique.  You wouldn't want the same IP address on different macs..



  • I agree with what everyone is saying but there is a way to assign the same static IP to two different MACs. I do it if I assign a static IP to a device that has multiple interfaces (WDTV, Roku 3, TVs, Work Laptop)

    This is not supported by pfsense and could break your system if you mess up!!! I hold no responsible if you break your system nor do I offer support. But I am willing to share the knowledge of how it can be done

    You will have have to manually edit your config.xml… Goto you the <dhcpd>section then look for <staticmap>... You should get the idea of how to do this...Once you save your changes, reboot your box..

    
    			 <staticmap><mac>00:19:9d:12:9f:4c</mac>
    				<ipaddr>192.168.0.51</ipaddr>
    				<hostname>vizio</hostname>
    
    				 <filename><rootpath></rootpath></filename></staticmap> 
    			 <staticmap><mac>00:19:9d:08:dc:05</mac>
    				<ipaddr>192.168.0.51</ipaddr>
    				<hostname>vizio</hostname></staticmap> 
    
    


    </staticmap></dhcpd>


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