Why is there a delay with no shut command on a serial interface?

So yesterday I was troubleshooting an issue with a distant end and had to change the interface (from shut to no shut) and protocol (ppp to hdlc) on a serial interface on a Tier 2 Cisco Router.

I was under the gun and for some reason it seems like I waited a few minutes when waiting to see that glorious up/up on that Serial Interface.

Chris Bryant talked about this on his Train Signal DVD. If you change the open/close the interface and/or change the protocol, stick around a few minutes to confirm that it is correct. However he didn't go into the why. I Googled around and couldn't find an answer and was wondering if anyone knew why there is some time delay with this.

thanks

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Comments

ciscoman2012

Hmm I would like to know the answer too.

The only thing I know is that Chris Bryant is the sh!t

ChickenNuggetz

JockVSJock wrote: »

So yesterday I was troubleshooting an issue with a distant end and had to change the interface (from shut to no shut) and protocol (ppp to hdlc) on a serial interface on a Tier 2 Cisco Router.

I was under the gun and for some reason it seems like I waited a few minutes when waiting to see that glorious up/up on that Serial Interface.

Chris Bryant talked about this on his Train Signal DVD. If you change the open/close the interface and/or change the protocol, stick around a few minutes to confirm that it is correct. However he didn't go into the why. I Googled around and couldn't find an answer and was wondering if anyone knew why there is some time delay with this.

thanks

I'm assuming this was a lab set-up that you're playing around with. If it is, the delay could be on account of the DTE/DCE clock rates synchronizing.

JockVSJock

ChickenNuggetz wrote: »

I'm assuming this was a lab set-up that you're playing around with.

This is actual production equipment.