"no keepalive" and "no shutdown" command on router and switch interface

[nitass]

Hello

I am confused about the “no keepalive” and “no shutdown” command on different interface type on router. In serial interface, the status is down/down. But in ethernet interface, it is up/up. Could anyone please clear me?

And can this reason apply with Catalyst too?

Thanks a lot,

Nitass

[amit-singh]

Hi Nitaas,

"No keepalive" and No shutdown they both have diffrent use.

Keepalives are used on the routers interfaces as hello mechanism to check the end to end connectivity to the other end.Routers interface used this mechanism to check the interface status.If you have no keepalive command its means that inerface status check mechansim in disabled and router will not transmit any keepalive packet on the link.

No shutdown cmmand is used to bring the interface up from the administratively shutdown state or the shutdown state on an interface which default on the routers. When the routers come up they put the interfaces in the shutdown state and you give the "no shut " command to bring the interface up.

Now, on the fastethernet interfaces the moment you give the no shut command it will bring the interface up but will not come up/up untill you connect the cable to it. On the serial interface if you dont have end to end connectivity through it will be down/down if keep alives are diabled. If keepalive is enable and you have ur CSU/DSU connected it will come up/down untill the connectivity is through.

HTH,

-amit singh

[nitass]

Hi amit-singh,

Thanks for reply. I have been set "no keepalive" command on ethernet interface of router for bringing interface to up/up even if it does not have cable connect to it.

So I want to know this case can apply to serial interface of router and ethernet interface of layer 3 switch too or not.

Thanks a lot,

Nitass

[amit-singh]

Hi Nitass,

Yes I see the same on my router.

OKH-PBAGH-GRGNPRNT#sh int fa 0/1

FastEthernet0/1 is up, line protocol is down

Hardware is AmdFE, address is 000b.5faa.6961 (bia 000b.5faa.6961)

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

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

Encapsulation ARPA, loopback not set

Keepalive set (10 sec)

OKH-PBAGH-GRGNPRNT(config)#int fa 0/1

OKH-PBAGH-GRGNPRNT(config-if)#no kee

OKH-PBAGH-GRGNPRNT(config-if)#no keepalive

OKH-PBAGH-GRGNPRNT(config-if)#end

OKH-PBAGH-GRGNPRNT#show int fa 0/1

FastEthernet0/1 is up, line protocol is up

Hardware is AmdFE, address is 000b.5faa.6961 (bia 000b.5f

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

I dont have a cable connected to it.

But its not the same on the serial interface and the ethernet interface of the L3 switch. They have different behaviur then this.they stay down/down.

PJB-UPW-PRI#sh int s 0/4

Serial0/4 is down, line protocol is down

Hardware is GT96K Serial

MTU 1500 bytes, BW 1544 Kbit, DLY 20000 usec,

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

Encapsulation HDLC, loopback not set

Keepalive set (10 sec)

PJB-UPW-PRI(config)#int s 0/4

PJB-UPW-PRI(config-if)#no kee

PJB-UPW-PRI(config-if)#no keepalive

PJB-UPW-PRI(config-if)#end

PJB-UPW-PRI#sh int s 0/4

Serial0/4 is down, line protocol is down

Hardware is GT96K Serial

MTU 1500 bytes, BW 1544 Kbit, DLY 20000 usec,

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

Encapsulation HDLC, loopback not set

Keepalive not set

4510_Switch_C48_BASEMENT(config)#int gig 3/19

4510_Switch_C48_BASEMENT(config-if)no keepalive

4510_Switch_C48_BASEMENT(config-if)#end

4510_Switch_C48_BASEMENT#show int g 3/19

GigabitEthernet3/19 is down, line protocol is down (notconnect)

Hardware is Gigabit Ethernet Port, address is 0013.7f65.4582 (b

82)

MTU 1500 bytes, BW 1000000 Kbit, DLY 10 usec,

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

Encapsulation ARPA, loopback not set

Keepalive set (10 sec)

HTH,

-amit singh

[nitass]

Hi amit-singh,

Thank you very much. Do you know the reason?

Thanks a lot,

Nitass

[MATTHIAS SCHAERER]

Nitass,

the serial interfaces rely on the modem signals to detect their status. On the bottom of the "sh int" output you see the signals and when DCD is down the interface is considered down regardless of the keepalive setting.

HTH

Mat

[nitass]

Hi mdschaerer,

Sorry to my late. I had Internet access limitation on last week. Thank you very much for reply.

Do you know the reason for Ethernet interface on Catalyst switch?

Thanks for advance,

Nitass

[Ravi Singh]

no keepalive: - It's used to determine whether the other end is there or not. If  you start with a switch with nothing plugged into it.  And look at  "show interface status", you'll see things are not-connected.  Even  though ports on a switch aren't shutdown by default, they are still not  UP because nothing's plugged in.  When you plug something in that changes.

If  you were to do "no keepalive" the ports would all show as "up/up" since  you lost your ability to determine whether it was REALLY functional or  not.

no shutdown:- This command is used to bring the interface up from the administratively  shutdown state or the shutdown state on an interface which default on  the routers. When the routers come up they put the interfaces in the  shutdown state and you give the "no shut " command to bring the  interface up.