Serial Interfaces' Dependencies

Unanswered Question
Nov 28th, 2007
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Hello NetPros,


As anyone come across issues where a serial connection (say s0/1) going down, tend to bring down another serial connection.


The scenerio is that, say RouterA has 2 serial interfaces s0/1 and s0/2. s0/1 is a ppp connection via a V100 satellite link, and s0/2 is a frame-relay connection with several subinterfaces ... Say s0/2.1,s0/2.2,s0/2.3,s0/2.4,s0/2.5 etc.


The problem is, whenever s0/1 goes down, it takes s0/2 main interface down with it, which in turn take down all the sub-interfaces with it.


Is there any reason why this should be, I'm guessing hardware related fault on the Hub Router, or a software bug ... Anyone come across this, please let me know.


!

interface Serial0/1

bandwidth 512

ip address A.B.C.D W.X.Y.Z

encapsulation ppp

ip route-cache flow

no fair-queue

no cdp enable

!


!

interface Serial0/2

bandwidth 2048

no ip address

encapsulation frame-relay IETF

ip route-cache flow

no ip route-cache cef

frame-relay traffic-shaping

frame-relay lmi-type ansi

frame-relay interface-queue priority 10 20 30 40

!

interface Serial0/2.1 point-to-point

bandwidth 128

ip address B.B.C.D W.X.Y.Z

no cdp enable

frame-relay interface-dlci 1

class 64k_cir_128k_bc

!

interface Serial0/2.2 point-to-point

bandwidth 128

ip address B.B.C.E W.X.Y.Z

no cdp enable

frame-relay interface-dlci 2

class 64k_cir_128k_bc

!

interface Serial0/2.3 point-to-point

bandwidth 128

ip address B.B.C.F W.X.Y.Z

no cdp enable

frame-relay interface-dlci 3

class 64k_cir_128k_bc

!

!

interface Serial0/2.4 point-to-point

bandwidth 128

ip address B.B.C.G W.X.Y.Z

no cdp enable

frame-relay interface-dlci 4

class 64k_cir_128k_bc

!

interface Serial0/2.5 point-to-point

bandwidth 128

ip address B.B.C.H W.X.Y.Z

shutdown

no cdp enable

frame-relay interface-dlci 5

class 64k_cir_128k_bc

!

interface Serial0/2.6 point-to-point

bandwidth 256

ip address B.B.C.I W.X.Y.Z

no cdp enable

frame-relay interface-dlci 6

class 128k_cir_256k_bc

!

interface Serial0/2.7 point-to-point

bandwidth 128

ip address B.B.C.J W.X.Y.Z no cdp enable

frame-relay de-group 1 7

frame-relay interface-dlci 7 IETF

class 64k_cir_128k_bc_inc_2_voice

vofr data 4 call-control 5

frame-relay payload-compression FRF9 stac

!

interface Serial0/2.8 point-to-point

bandwidth 32

no cdp enable

frame-relay interface-dlci 8

class 56k_cir_7k_bc_2_voice

vofr data 5 call-control 4

!

Many Thanks

Yemi Salau



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Richard Burts Wed, 11/28/2007 - 03:50
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Yemi


Some additional information would be helpful. What platform is this running on? Are both serial interfaces on the same card (from the interface addressing I would assume so)? What kind of card is it? Does it happen all the time that if serial0/1 goes down that serial0/2 also goes down or is it sometimes?


HTH


Rick

salau Wed, 11/28/2007 - 04:01
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Thanks Rick,


Here is a sh ver:


Cisco IOS Software, 3700 Software (C3745-JSX-M), Version 12.3(7)T, RELEASE SOFTW

ARE (fc1)

Technical Support: http://www.cisco.com/techsupport

Copyright (c) 1986-2004 by Cisco Systems, Inc.

Compiled Sat 21-Feb-04 05:53 by eaarmas


ROM: System Bootstrap, Version 12.2(8r)T2, RELEASE SOFTWARE (fc1)


RouterA uptime is 6 weeks, 17 hours, 32 minutes

System returned to ROM by reload at 19:32:39 bst Tue Oct 16 2007

System restarted at 19:35:03 bst Tue Oct 16 2007

System image file is "flash:c3745-jsx-mz.123-7.T.bin"


Cisco 3745 (R7000) processor (revision 2.0) with 116736K/14336K bytes of memory.

Processor board ID JHY0753K01M

R7000 CPU at 350MHz, Implementation 39, Rev 3.3, 256KB L2, 2048KB L3 Cache

2 FastEthernet interfaces

6 Serial(sync/async) interfaces

1 ATM interface

8 Voice FXO interfaces

DRAM configuration is 64 bits wide with parity disabled.

151K bytes of NVRAM.

31744K bytes of ATA System CompactFlash (Read/Write)


Configuration register is 0x2102



***************************************************


1. Yes, Both Serial interfaces are on the same module. Hardware is GT96K Serial WIC

2. This happen all the time if s0/1 goes down due to various reasons like weather(since it's a satellite V100 link), then s0/2 will go down as well.


Cheers

Yemi

Richard Burts Wed, 11/28/2007 - 04:13
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Yemi


Thank you for the additional information. I find it very unusual that the second interface always goes down if the first one goes down, especially for reasons such as weather affecting satellite. If serial0/2 goes down does it take down serial0/1?


I would be inclined to open a case with TAC if there is a maintenance contract on this router. If a TAC case is not possible I would try upgrading the software on the possibility that it might be a software issue.


HTH


Rick

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