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Posted on 2011-09-18
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Last Modified: 2012-06-27
I three routers and I wanted to know why the serial links are up/down...can't figure this one out.  Here are the attachments and outputs.  Also, instead of having: int s0/0/1 it's s0/1 for example. Net. topology R1.txt R2.txt R3.txt
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Question by:ee4itpro
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18 Comments
 
LVL 17

Expert Comment

by:rochey2009
ID: 36557308
Hi,

Try specifying the clock rate only on the DCE interfaces and not on the DTE end of each link i.e. remove the clock rate statements from each of the DTE interfaces.
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Author Comment

by:ee4itpro
ID: 36557628
how do i know which one is the DTE device/s?
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LVL 12

Expert Comment

by:Steve
ID: 36558252
In your example the DTE devices would be  R1 and R3

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LVL 17

Expert Comment

by:MAG03
ID: 36558624
you can find out which devices are DTE and DCE by issuing the show controllers serial 0/0 command from enabled mode. However, the clock rate should not affect the link if it is configured on the DTE interfaces, it should just be ignored.

I just entered your config into my setup and it works fine. Perhaps your routers are more fussy than mine.  I noticed that your serial0/1 interface on R2 has a different bandwidth than on R3 serial 0/0. Shouldn't really have anything to do with it, but try matching up your interface commands exaclty.

Have you tried to shutdown the interfaces and then bring them back up?

is the link showing up down on all serial interfaces or just between two of the routers?

are you using any other config such as PPP or frame-relay that is omitted from the config output?

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LVL 17

Expert Comment

by:rochey2009
ID: 36559116
What type of serial cable are you using?
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Author Comment

by:ee4itpro
ID: 36561952
I'm getting this from the Cisco Lab book, Lab 2-3

The issues seems to be that altough the serial links on s0/1 are up for about a minute or two, they drop after this time, but I don't know why or how to fix.

Any ideas?
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Author Comment

by:ee4itpro
ID: 36562064
This is what I got after performing a shutdown and then no shutdown on the s0/1 interface on both R2 and R3.  I then tried the command:   debug eigrp packets query reply

This is the output of the command on R2:

R2#config t
Enter configuration commands, one per line.  End with CNTL/Z.
R2(config)#int s0/1
R2(config-if)#shutdown
R2(config-if)#no shut
R2(config-if)#
*Mar  1 00:19:36.383: %LINK-5-CHANGED: Interface Serial0/1, changed state to adm                                                                              inistratively down
R2(config-if)#exit
R2(config)#
*Mar  1 00:19:39.807: %LINK-3-UPDOWN: Interface Serial0/1, changed state to up
R2(config)#
R2(config)#
*Mar  1 00:19:40.811: %LINEPROTO-5-UPDOWN: Line protocol on Interface Serial0/1,                                                                               changed state to up
R2(config)#
R2(config)#
R2(config)#
R2(config)#
R2(config)#
R2(config)#
R2(config)#
*Mar  1 00:20:06.751: %LINEPROTO-5-UPDOWN: Line protocol on Interface Serial0/1,                                                                               changed state to down
R2(config)#
*Mar  1 00:20:06.771: EIGRP: Enqueueing QUERY on Serial0/0 iidbQ un/rely 0/1 ser                                                                              no 13-13
*Mar  1 00:20:06.775: EIGRP: Enqueueing QUERY on Serial0/0 nbr 192.168.100.1 iid                                                                              bQ un/rely 0/0 peerQ un/rely 0/0 serno 13-13
*Mar  1 00:20:06.779: EIGRP: Sending QUERY on Serial0/0 nbr 192.168.100.1
*Mar  1 00:20:06.779:   AS 100, Flags 0x0, Seq 7/5 idbQ 0/0 iidbQ un/rely 0/0 pe                                                                              erQ un/rely 0/1 serno 13-13
*Mar  1 00:20:06.867: EIGRP: Received REPLY on Serial0/0 nbr 192.168.100.1
*Mar  1 00:20:06.867:   AS 100, Flags 0x0, Seq 7/7 idbQ 0/0 iidbQ un/rely 0/0 pe      
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LVL 17

Expert Comment

by:rochey2009
ID: 36563161
Are these real routers, back to back or are you using an emulator?
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Author Comment

by:ee4itpro
ID: 36563587
Using gns
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LVL 17

Expert Comment

by:rochey2009
ID: 36563732
Hi,

Try removing all of the clock rate commands off each serial interface on both ends of each link.
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Expert Comment

by:MAG03
ID: 36565119
I would say copy the configs into notepad. Stop and restart the routers and then copy them back and test.
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Author Comment

by:ee4itpro
ID: 36568130
I tried both Rockey2009 and MAG03's suggestions, but the same result occured.  Seems as though the serial 0/1 is still UP/DOWN.  The protocol is in a DOWN STATE.
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LVL 17

Expert Comment

by:rochey2009
ID: 36568241
which router and IOS are you using in GNS3?
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Author Comment

by:ee4itpro
ID: 36568364
I'm using the c2691 router in GNS.

Cisco IOS Software, 2600 Software (C2691-ADVENTERPRISEK9-M), Version 12.4(23), RELEASE SOFTWARE (fc1)
Technical Support: http://www.cisco.com/techsupport
Copyright (c) 1986-2008 by Cisco Systems, Inc.
Compiled Sat 08-Nov-08 21:17 by prod_rel_team

Cisco 2691 (R7000) processor (revision 0.1) with 124928K/6144K bytes of memory.
Processor board ID XXXXXXXXXXX
R7000 CPU at 160MHz, Implementation 39, Rev 2.1, 256KB L2, 512KB L3 Cache
2 FastEthernet interfaces
2 Serial(sync/async) interfaces
DRAM configuration is 64 bits wide with parity enabled.
55K bytes of NVRAM.
16384K bytes of ATA System CompactFlash (Read/Write)

Configuration register is 0x2102
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Author Comment

by:ee4itpro
ID: 36568531
I also tried this on a 7200 router, but the same result.  The serial link from R2 to R3 seems to be down for some reason, but don't know why.  

Am I missing something here?
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Accepted Solution

by:
rochey2009 earned 500 total points
ID: 36568872
Make sure that ser0/1 on R2 is connected to ser0/1 on R3 and not ser0/0 on R3.

If you hover over the serial link it should tell you which port on R2 is connected to which port on R3.
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Author Comment

by:ee4itpro
ID: 36578382
Rochey2009,

This was it!!! I'm new to GNS3 and when I hovered over the serial links on GNS, I was able to confirm the proper links...s1/0, s1/0 and so forth.

Thanks!
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LVL 17

Expert Comment

by:MAG03
ID: 36578597
Just for future reference there is a button selection at the top of GNS3 that is called Show Interface Labels that will show which interfaces are connected to a certain link.
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