Interface Flapping

[ChrisAC]

Ok guys! Further to my previous posts regarding the flapping of the serial interface on a customer router, we're still having problems!

The network is up and running but the interface is up and down like a yo-yo. Doing a "debug serial interfaces" we get the following output:

01:06:07: %QUICC_ETHER-1-LOSTCARR: Unit 0, lost carrier. Transceiver problem?
01:06:17: QUICC_SERIAL(0): Reset from 0x2352330
01:06:18: %LINEPROTO-5-UPDOWN: Line protocol on Interface Serial0, changed state to down
01:06:19: %LINK-3-UPDOWN: Interface Serial0, changed state to up
01:06:24: %LINEPROTO-5-UPDOWN: Line protocol on Interface Serial0, changed state to up
01:07:07: %QUICC_ETHER-1-LOSTCARR: Unit 0, lost carrier. Transceiver problem?
01:07:17: QUICC_SERIAL(0): Reset from 0x2352330
01:07:18: %LINEPROTO-5-UPDOWN: Line protocol on Interface Serial0, changed state to down
01:07:19: %LINK-3-UPDOWN: Interface Serial0, changed state to up
01:07:24: %LINEPROTO-5-UPDOWN: Line protocol on Interface Serial0, changed state to up
01:08:07: %QUICC_ETHER-1-LOSTCARR: Unit 0, lost carrier. Transceiver problem?
01:08:17: QUICC_SERIAL(0): Reset from 0x2352330

The core router config looks okay! The keepalives are correct at both ends. We've put loopbacks tests on various parts on the circuit and everything check out!! But, it still keeps bouncing!

Any ideas anyone!! We've been on with this all morning and we're getting nowhere fast!

Cheers.

Chris. ********************************
Chris Andrew, CCNA
Technical Support Engineer
********************************

 

[BOJIKA]

show configs...

 

[wybnormal]

Let me guess... you are using unnumbered IP and using the E0 as the source? I see the printout shows the E0 as down.. then the serial drops off line, tries to come back up and goes back down again.

If this is true... set up a loopback address for the unnumbered to use.. and find out why E0 is down

Just a guess based on limited info ;-)

MikeS Find me at

http://www.packetattack.com

"Diplomacy; the art of saying 'nice doggie' till you can find a rock" Wynn Catlin

 

[ChrisAC]

Yeah, it's IP unnumbered eth0! However, this problem has occured while eth0 was up and on the network. We could get to the router this morning and look at the config. However, the serial interface was showing over 2,500 interface resets! The core guys have confirmed that the core router to which this is terminated on is showing carrier transitions! We re-set the counters and then saw a reset every minute!

We've just had the NTU swapped out at the customer end and have tried another router and another X.21 cable.

Strange one this!!

Chris.
********************************
Chris Andrew, CCNA
Technical Support Engineer
********************************

 

[ChrisAC]

It's now been decided to change the line to another bearer on another router. We've changed just about everything else!

If/when we solve this one (hopefully tomorrow) I'll let you know what the problem is/was!!

Chris.
********************************
Chris Andrew, CCNA
Technical Support Engineer
********************************

 

[ChrisAC]

Sorted!!

The line was changed to another bearer on another router and all is well again!!

Looks like we'll have to take the faulty bearer down at some point to investigate!

Chris.
********************************
Chris Andrew, CCNA
Technical Support Engineer
********************************

 

[wybnormal]

Cool- it's always nice to hear that something got fixed..sorta of Dont you just love the cut and dried world of networks...

MikeS Find me at

http://www.packetattack.com

"Diplomacy; the art of saying 'nice doggie' till you can find a rock" Wynn Catlin

 

[ChrisAC]

It was a strange one! Bearers don't go faulty very often so it was a bit of a supprise! In fact non of the Cisco kit usually develops faults. Nine times out of ten the problem is with either the line (NTE's can go faulty and loose their sync) or with the networks behind the routers. We can always guarantee that if a customer has a problem with, say a mail server or internet access, the first thing they blame is the leased line!! Can't get on the internet ... the line must be faulty!! Can't receive e-mail .. the line must be faulty! Makes me soooo mad!!

This time it was our fault .. and we knew it!! Ooops!!

Cheers guys!!

Chris.
********************************
Chris Andrew, CCNA
Technical Support Engineer
********************************