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    Interface gets pinged even when cable not connected

    Scheduled Pinned Locked Moved General pfSense Questions
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    • B Offline
      bhawk6901
      last edited by

      We are usinng soekris net 6501-70 boards and just today i stumbled upon this strange phenomena. I disconnected the cable from one of the interfaces and pinged it randomly and was surprised to get a reply. The cable was disconnected no doubt about that. Should this happen? If not whats wrong ?

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      • johnpozJ Online
        johnpoz LAYER 8 Global Moderator
        last edited by

        Yes the packets magically flow through the air to the interface.

        You either had a different path to get to the ip than you thought, or your were pinging something else then what you thought you were pinging.

        An intelligent man is sometimes forced to be drunk to spend time with his fools
        If you get confused: Listen to the Music Play
        Please don't Chat/PM me for help, unless mod related
        SG-4860 24.11 | Lab VMs 2.8, 24.11

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        • H Offline
          heper
          last edited by

          you got a rogue device on the network that is using the same ip

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          • KOMK Offline
            KOM
            last edited by

            you got a rogue device on the network that is using the same ip

            But if that were the case, he would be seeing all kinds of network issues.

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            • johnpozJ Online
              johnpoz LAYER 8 Global Moderator
              last edited by

              Another possible issue could be that some sort of vip/hsrp/carp setup where another interface picks up that IP you were pinging.

              Maybe he was having issues with his network, which is why he disconnected the wire with the IP the thought was having a problem and it still pings the other device using that IP, etc.

              We have no details on the configuration, no details of any kind to be honest.  But what I can tell you for FACT is you have this

              deviceA –-- switch --- deviceB and unplug either of those then its not going to be possible to ping.. So either there is another path that you didn't know you were using, or your not pinging the device you thought you were pinging, etc..

              Unless the packets are magically spanning the air gap that was created ;)

              An intelligent man is sometimes forced to be drunk to spend time with his fools
              If you get confused: Listen to the Music Play
              Please don't Chat/PM me for help, unless mod related
              SG-4860 24.11 | Lab VMs 2.8, 24.11

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              • B Offline
                bhawk6901
                last edited by

                @johnpoz:

                Yes the packets magically flow through the air to the interface.

                You either had a different path to get to the ip than you thought, or your were pinging something else then what you thought you were pinging.

                there is absolutely no path possible. I pulled a device d  :-\ :-\ :-\from the rack and connected to my PC via one interface, all other interfaces were disconnected  :-\

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                • D Offline
                  doktornotor Banned
                  last edited by

                  Yeah, call ghostbusters. Or stop smoking that stuff, it's too strong.

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                  • DerelictD Offline
                    Derelict LAYER 8 Netgate
                    last edited by

                    Do it again, ping, look at the ARP table, get the MAC address for the IP you're magically pinging and track it down.

                    Is there Wi-Fi involved anywhere?

                    Chattanooga, Tennessee, USA
                    A comprehensive network diagram is worth 10,000 words and 15 conference calls.
                    DO NOT set a source address/port in a port forward or firewall rule unless you KNOW you need it!
                    Do Not Chat For Help! NO_WAN_EGRESS(TM)

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                    • johnpozJ Online
                      johnpoz LAYER 8 Global Moderator
                      last edited by

                      Think about it for all of 2 seconds dude…  If you have something connected with a wire with no other paths to it..  And you can still ping that IP.. you either have another path to that IP.. Or your pinging something else that answers to that IP..

                      Or by some crazy odd weird magic your packets are jumping the air gap and flowing through the air??

                      What is more logical your over looking a path or pinging something else with that same ip???  My vote is your over looking something... Come on... packets don't magically flow over the air gap...

                      Just think about it for 2 freaking seconds...  That you even posted this thread points to your high on something or not thinking straight or just some lame attempt at trolling.

                      An intelligent man is sometimes forced to be drunk to spend time with his fools
                      If you get confused: Listen to the Music Play
                      Please don't Chat/PM me for help, unless mod related
                      SG-4860 24.11 | Lab VMs 2.8, 24.11

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                      • B Offline
                        bhawk6901
                        last edited by

                        Since nobody believes me yet, i'm posting a diagram what I am doing now to clarify things.
                        Eth0 ip: 192.168.1.1/24
                        PC1 ip: 192.168.1.10/24
                        Eth1 ip: 192.168.2.1/24
                        PC2 ip: 192.168.2.10/24

                        Disconnected the cable between Eth0 & PC1
                        Ping Eth0 from PC2 and it gets pinged

                        Untitled.png_thumb
                        Untitled.png

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                        • DerelictD Offline
                          Derelict LAYER 8 Netgate
                          last edited by

                          pfSense does not take interface IP addresses down when ethernet carrier is lost like, say, a Cisco does.

                          In fact, the interface addresses actually route to loopback interfaces internally.

                          What you're seeing is completely normal.  You can ping a local interface address even though the interface has nothing plugged into it.  Your initial description had everyone thinking you were saying you could still ping 192.168.1.1 from 192.168.1.10 even though it was unplugged.

                          Amazing how a diagram clears things up immediately.

                          Chattanooga, Tennessee, USA
                          A comprehensive network diagram is worth 10,000 words and 15 conference calls.
                          DO NOT set a source address/port in a port forward or firewall rule unless you KNOW you need it!
                          Do Not Chat For Help! NO_WAN_EGRESS(TM)

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                          • S Offline
                            Supermule Banned
                            last edited by

                            HAHAHAHAHAHAHAHAH

                            You gotta be kidding :D

                            Your pinging the interface INSIDE the Soekris box. You need to ping 192.168.1.10 to see the result of you pulling the cable. Try to disable the interface in pfsense and your ping will be gone ;)

                            :D

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                            • DerelictD Offline
                              Derelict LAYER 8 Netgate
                              last edited by

                              I don't think it's that funny.  A Cisco takes the local interface IP address down if it loses carrier, at least by default.

                              Chattanooga, Tennessee, USA
                              A comprehensive network diagram is worth 10,000 words and 15 conference calls.
                              DO NOT set a source address/port in a port forward or firewall rule unless you KNOW you need it!
                              Do Not Chat For Help! NO_WAN_EGRESS(TM)

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                              • M Offline
                                maverick_slo
                                last edited by

                                No this II funny :)

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                                • D Offline
                                  doktornotor Banned
                                  last edited by

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                                  • DerelictD Offline
                                    Derelict LAYER 8 Netgate
                                    last edited by

                                    Difference of opinion on how a router should actually behave I guess.  Neither behavior is wrong.  But I would bet the pfSense guys would welcome more Cisco-like behavior if FreeBSD were to implement it.  Optional, of course.

                                    Anyway, OP, the reason these guys are bagging on you is easily answered by looking at your diagram.  See the ping source, then the ping response, then the connection break FURTHER down the path?

                                    There is really no reason for the router not to respond.  The connection break is the next hop.

                                    (Cisco routers do respond in this situation BTW, with an ICMP Destination Unreachable)

                                    
                                    R2-2620#ping 192.168.1.1
                                    
                                    Type escape sequence to abort.
                                    Sending 5, 100-byte ICMP Echos to 192.168.1.1, timeout is 2 seconds:
                                    U.U.U
                                    
                                    

                                    Chattanooga, Tennessee, USA
                                    A comprehensive network diagram is worth 10,000 words and 15 conference calls.
                                    DO NOT set a source address/port in a port forward or firewall rule unless you KNOW you need it!
                                    Do Not Chat For Help! NO_WAN_EGRESS(TM)

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                                    • H Offline
                                      Harvy66
                                      last edited by

                                      Interface IPs going down can mess with services on the firewall box making is more likely for a service to not rebind to the IP when the interface comes back up. Many services get around this by restarting when a new interface comes up. Many sandbox setups will drop privileges to bind interfaces once the software initializes, meaning the software can't bind to a new IP.

                                      There's many fewer corner cases if you just let the IP stay on the interface even when it's not plugged in. Use a heart beat if you need to check uplink status.

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                                      • M Offline
                                        mer
                                        last edited by

                                        Maybe if one does ifconfig down on the interface after you pull the cable, you get the desired response.

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                                        • DerelictD Offline
                                          Derelict LAYER 8 Netgate
                                          last edited by

                                          Interface IPs going down can mess with services on the firewall box making is more likely for a service to not rebind to the IP when the interface comes back up.

                                          I can certainly see that being a problem.

                                          Chattanooga, Tennessee, USA
                                          A comprehensive network diagram is worth 10,000 words and 15 conference calls.
                                          DO NOT set a source address/port in a port forward or firewall rule unless you KNOW you need it!
                                          Do Not Chat For Help! NO_WAN_EGRESS(TM)

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                                          • johnpozJ Online
                                            johnpoz LAYER 8 Global Moderator
                                            last edited by

                                            since when would these IPs go down even in a cisco switch.. Normally your ip would be on loopback or svi, not actually tied to any physical interface..  Can not remember putting an IP on the actual interface before in cisco..  If you were running services on a cisco switch like dhcp or routing even that would be over a SVI, not actually tied to a physical interface being up or down..

                                            An intelligent man is sometimes forced to be drunk to spend time with his fools
                                            If you get confused: Listen to the Music Play
                                            Please don't Chat/PM me for help, unless mod related
                                            SG-4860 24.11 | Lab VMs 2.8, 24.11

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