11 Replies Latest reply: Aug 12, 2014 3:42 AM by lionelnetwork RSS

    Keep an Ethernet Interface UP/UP

    Jonathan Stevenson

      Hey folks, Does anyone know of a way to force an Ethernet interface to remain in the UP/UP state - even if it is disconnected?  I know it invites it's own problems but I've been asked to do this because that interface is being used for remote management.

       

      It's on a 1941  (C1900-UNIVERSALK9-M), Version 15.1(4)M2

       

       

      Cheers

        • 1. Re: Keep an Ethernet Interface UP/UP
          Jonathan Stevenson

          I have <no keepalives> configured on the interface by the way and it doesn't work

          • 2. Re: Keep an Ethernet Interface UP/UP
            Sey

            interface Gi0/0

            no keepalive

             

            It works for me on a 3845.

            • 3. Re: Keep an Ethernet Interface UP/UP
              arteq

              doesn't seem to work on a 2950 sw...

               

              sw2950_02#sh int fa0/5

              FastEthernet0/5 is down, line protocol is down (notconnect)

                Hardware is Fast Ethernet, address is 0009.b73f.ce85 (bia 0009.b73f.ce85)

                MTU 1500 bytes, BW 10000 Kbit, DLY 1000 usec,

                   reliability 255/255, txload 1/255, rxload 1/255

                Encapsulation ARPA, loopback not set

                Keepalive set (10 sec)

                Full-duplex, 100Mb/s, media type is 100BaseTX

                input flow-control is unsupported output flow-control is unsupported

                ARP type: ARPA, ARP Timeout 04:00:00

                Last input never, output 3d16h, output hang never

                Last clearing of "show interface" counters never

                Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0

                Queueing strategy: fifo

                Output queue: 0/40 (size/max)

                5 minute input rate 0 bits/sec, 0 packets/sec

                5 minute output rate 0 bits/sec, 0 packets/sec

                   0 packets input, 0 bytes, 0 no buffer

                   Received 0 broadcasts (0 multicast)

                   0 runts, 0 giants, 0 throttles

                   0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored

                   0 watchdog, 0 multicast, 0 pause input

                   0 input packets with dribble condition detected

                   0 packets output, 0 bytes, 0 underruns

               

               

              sw2950_02#config t

              Enter configuration commands, one per line.  End with CNTL/Z.

              sw2950_02(config)#int fa0/5

              sw2950_02(config-if)#no keepalive

              sw2950_02(config-if)#do sh int fa0/5

              FastEthernet0/5 is down, line protocol is down (notconnect)

                Hardware is Fast Ethernet, address is 0009.b73f.ce85 (bia 0009.b73f.ce85)

                MTU 1500 bytes, BW 10000 Kbit, DLY 1000 usec,

                   reliability 255/255, txload 1/255, rxload 1/255

                Encapsulation ARPA, loopback not set

                Keepalive not set

                Full-duplex, 100Mb/s, media type is 100BaseTX

                input flow-control is unsupported output flow-control is unsupported

                ARP type: ARPA, ARP Timeout 04:00:00

                Last input never, output 3d16h, output hang never

                Last clearing of "show interface" counters never

                Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0

                Queueing strategy: fifo

                Output queue: 0/40 (size/max)

                5 minute input rate 0 bits/sec, 0 packets/sec

                5 minute output rate 0 bits/sec, 0 packets/sec

                   0 packets input, 0 bytes, 0 no buffer

                   Received 0 broadcasts (0 multicast)

                   0 runts, 0 giants, 0 throttles

                   0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored

                   0 watchdog, 0 multicast, 0 pause input

                   0 input packets with dribble condition detected

                   0 packets output, 0 bytes, 0 underruns

              --More--

              • 4. Re: Keep an Ethernet Interface UP/UP
                Jonathan Stevenson

                interface GigabitEthernet0/0

                duplex auto

                speed auto

                no keepalive

                end

                 

                ***DISCONNECT G0/0***

                 

                Jan 24 15:22:47: %LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet0/0, changed state to down

                Jan 24 15:22:48: %LINK-3-UPDOWN: Interface GigabitEthernet0/0, changed state to down

                 

                RTGP100A1R1(config-if)#do sh ip int br

                 

                Interface                  IP-Address      OK? Method Status                Protocol

                Embedded-Service-Engine0/0 unassigned      YES unset  administratively down down

                GigabitEthernet0/0         ***********     YES NVRAM  down                  down

                GigabitEthernet0/1         unassigned      YES NVRAM  administratively down down

                Dialer1                    unassigned      YES NVRAM  up                    up

                Loopback0                  ***********     YES NVRAM  up                    up

                Virtual-Access1            unassigned      YES unset  up                    up

                 

                 

                ***RECONNECT G0/0***

                 

                Jan 24 15:23:11: %LINK-3-UPDOWN: Interface GigabitEthernet0/0, changed state to up

                Jan 24 15:23:12: %LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet0/0, changed state to up

                 

                RTGP100A1R1(config-if)#do sh ip int br

                Interface                  IP-Address      OK? Method Status                Protocol

                Embedded-Service-Engine0/0 unassigned      YES unset  administratively down down

                GigabitEthernet0/0         ************    YES NVRAM  up                    up

                GigabitEthernet0/1         unassigned      YES NVRAM  administratively down down

                Dialer1                    unassigned      YES NVRAM  up                    up

                Loopback0                  ***********     YES NVRAM  up                    up

                Virtual-Access1            unassigned      YES unset  up                    up

                RTGP100A1R1(config-if)#

                • 5. Re: Keep an Ethernet Interface UP/UP
                  arteq

                  and on a 2620 router... it works.. go figure... see below... had to see it to believe it...the light goes out by the way, in either case...

                   

                  r2620_02#sh int fa0/0

                  FastEthernet0/0 is up, line protocol is down

                    Hardware is AmdFE, address is 0014.6ad0.da00 (bia 0014.6ad0.da00)

                    Internet address is 192.168.1.120/24

                    MTU 1500 bytes, BW 100000 Kbit, DLY 100 usec,

                       reliability 255/255, txload 1/255, rxload 1/255

                    Encapsulation ARPA, loopback not set

                   

                  r2620_02(config)#int fa0/0

                  r2620_02(config-if)#no keepalive

                  r2620_02(config-if)#end

                  r2620_02#sh int fa0/0

                  FastEthernet0/0 is up, line protocol is up

                    Hardware is AmdFE, address is 0014.6ad0.da00 (bia 0014.6ad0.da00)

                    Internet address is 192.168.1.120/24

                    MTU 1500 bytes, BW 100000 Kbit, DLY 100 usec,

                       reliability 255/255, txload 1/255, rxload 1/255

                    Encapsulation ARPA, loopback not set

                    Keepalive not set

                    Full-duplex, 100Mb/s, 100BaseTX/FX

                  • 6. Re: Keep an Ethernet Interface UP/UP
                    Jonathan Stevenson

                    I'm going to try a later version of the Universal IOS to make sure it's not a bug.

                    • 7. Re: Keep an Ethernet Interface UP/UP
                      Greg, CCNP, JNCIP

                      As networks grow and routers have more interfaces, most people find it simpler to manage their routers by configuring each with a loopback interface:

                      https://learningnetwork.cisco.com/message/124846#124846

                      • 8. Re: Keep an Ethernet Interface UP/UP
                        Paul Williams

                        Hi Johnny

                         

                        you should use a Loopback interface to manage the device as loopback interfaces are always up/up

                         

                        R1(config)#int loopback 1

                         

                        This will create the loopback interface and put you in to the interface config mode where you can ip the loopback interface.

                         

                        If this option is not avaliable for example on a switch you could just set an ip address on a Vlan Vlan1 for example

                         

                        SW1(config)#int vlan1

                        SW1(config-if)#ip address (ip) (sub net)

                         

                        Remeber to add a DG

                         

                        SW1(config)#ip default-gateway (ip)

                         

                        Hope ths helps

                         

                        Paul

                        • 9. Re: Keep an Ethernet Interface UP/UP
                          Jonny7_2002

                          I would agree with Paul. if you have a routing protocol configured then use a loopback and include the loopback IP in the network statements or the interface itself and then you can get to the router from any interface that is up (in Theory )

                           

                          Jon

                          • 10. Re: Keep an Ethernet Interface UP/UP
                            Dan Gaviuc

                            Hi, there are some devices which have a command on interface # - loopback. And that keep interface UP/UP

                            • 11. Re: Keep an Ethernet Interface UP/UP
                              lionelnetwork

                              Hi,

                               

                              Also ensure that the correct media type is indicated as GigabitEthernet0/0 on say CISCO3845 has both SFP and RJ45 ports.

                               

                              exp.

                               

                               

                              en

                              conf t

                              int GigabitEthernet0/0 

                              media-type sfp

                              ip add 10.0.0.** 255.255.255.0

                              no sh

                              exit

                              exit

                               

                              en

                              conf t

                              int GigabitEthernet0/0 

                              media-type rj45

                              ip add 10.0.0.** 255.255.255.0

                              no sh

                              exit

                              exit