Odd Problems with Serial Connection

numeric · 07-04-2009, 10:50 PM

Hi everyone,

I've been a member for a while, but haven't posted as I keep having to put off signing up for the course I want to take. I'm finally in a position where I'll be able to afford it and have decided to try and get a head start before I sign up.

To this end, I bought three 2500 series routers off ebay. Two of them work fine and I've had no problems, but the serial 0 interface on the third router (a 2504) refuses to stay up after a basic config. The link initially stays up for a short time before dropping and coming back up again. This happens at precise, regular intervals and has me pretty stumped. I don't think it's a problem with my config as I've been pretty careful, but I'll post them anyway.

I've tried swapping cables around and using a different router on both ends of the connection ( I'm using back to back DB60 cables), and I'm pretty sure it's the 2504 that is at fault . I'm only seeing error messages on the 2504, nothing from the other end of the link.

Hopefully someone can give me a bit of a hand

Firstly, here's the config from the 2504:

Code:

bottom#show start
Using 512 out of 32762 bytes
!
version 12.1
no service single-slot-reload-enable
service timestamps debug uptime
service timestamps log uptime
no service password-encryption
!
hostname bottom
!
!
!
!
!
!
ip subnet-zero
!
!
!
!
interface Serial0
 ip address 192.168.57.2 255.255.255.0
 no fair-queue
!
interface Serial1
 ip address 192.168.58.1 255.255.255.0
 clockrate 64000
!
interface TokenRing0
 no ip address
 shutdown
!
interface BRI0
 no ip address
 shutdown
!
ip classless
ip http server
!
!
line con 0
line aux 0
line vty 0 4
!
end

Here's the 2501 that's at the other end of the link:

Code:

middle#show start
Using 469 out of 32762 bytes
!
version 12.1
no service single-slot-reload-enable
service timestamps debug uptime
service timestamps log uptime
no service password-encryption
!
hostname middle
!
!
!
!
!
!
ip subnet-zero
!
!
!
!
interface Ethernet0
 no ip address
 shutdown
!
interface Serial0
 ip address 192.168.56.2 255.255.255.0
 no fair-queue
!
interface Serial1
 ip address 192.168.57.1 255.255.255.0
 clockrate 64000
!
ip classless
ip http server
!
!
line con 0
line aux 0
line vty 0 4
!

Lastly, Here's the messages that are being shown on the 2504 (nothing appears on the 2501)

Code:

00:02:17: %LINEPROTO-5-UPDOWN: Line protocol on Interface Serial0, changed state         to down
00:02:27: %LINEPROTO-5-UPDOWN: Line protocol on Interface Serial0, changed state         to up
00:02:47: %LINEPROTO-5-UPDOWN: Line protocol on Interface Serial0, changed state         to down
00:02:57: %LINEPROTO-5-UPDOWN: Line protocol on Interface Serial0, changed state         to up
00:03:17: %LINEPROTO-5-UPDOWN: Line protocol on Interface Serial0, changed state         to down
00:03:27: %LINEPROTO-5-UPDOWN: Line protocol on Interface Serial0, changed state         to up
00:03:47: %LINEPROTO-5-UPDOWN: Line protocol on Interface Serial0, changed state         to down
00:03:57: %LINEPROTO-5-UPDOWN: Line protocol on Interface Serial0, changed state         to up
00:04:17: %LINEPROTO-5-UPDOWN: Line protocol on Interface Serial0, changed state         to down

Any help here would be great - even if it's just to say that the interface is dying. I've posted on a couple of forums, but have had no success so far - hopefully I'll find an answer here

Cheers,

-n

captobvious · 07-04-2009, 11:22 PM

If these are truly your configs, here's a hint. The connections on each of the serial links should be in the same subnet.

numeric · 07-04-2009, 11:30 PM

On the connection in question, they are. Serial 0 on the 2504 is connected to Serial 1 on the 2501. I'll post the network diagram I drew out before I started - hopefully that will make it a bit clearer.

mikej412 · 07-05-2009, 12:03 AM

Post the output from the 2504 for
show controllers serial 0
show interface serial 0

numeric · 07-05-2009, 12:43 AM

Here's the output from the commands requested:

Code:

bottom#show controller ser 0
HD unit 0, idb = 0x122CC0, driver structure at 0x129048
buffer size 1524  HD unit 0, V.35 DTE cable
cpb = 0xE4, eda = 0xD814, cda = 0xD828
RX ring with 16 entries at 0xE4D800
00 bd_ptr=0xD800 pak=0x12AC38 ds=0xE52BF8 status=80 pak_size=22
01 bd_ptr=0xD814 pak=0x12A53C ds=0xE517C4 status=80 pak_size=22
02 bd_ptr=0xD828 pak=0x12A790 ds=0xE51E80 status=80 pak_size=0
03 bd_ptr=0xD83C pak=0x12A9E4 ds=0xE5253C status=80 pak_size=0
04 bd_ptr=0xD850 pak=0x12AE8C ds=0xE532B4 status=80 pak_size=0
05 bd_ptr=0xD864 pak=0x12B0E0 ds=0xE53970 status=80 pak_size=0
06 bd_ptr=0xD878 pak=0x12B334 ds=0xE5402C status=80 pak_size=0
07 bd_ptr=0xD88C pak=0x12B588 ds=0xE546E8 status=80 pak_size=0
08 bd_ptr=0xD8A0 pak=0x12B7DC ds=0xE54DA4 status=80 pak_size=0
09 bd_ptr=0xD8B4 pak=0x12BA30 ds=0xE55460 status=80 pak_size=0
10 bd_ptr=0xD8C8 pak=0x12BC84 ds=0xE55B1C status=80 pak_size=0
11 bd_ptr=0xD8DC pak=0x12BED8 ds=0xE561D8 status=80 pak_size=0
12 bd_ptr=0xD8F0 pak=0x12C12C ds=0xE56894 status=80 pak_size=0
13 bd_ptr=0xD904 pak=0x12C380 ds=0xE56F50 status=80 pak_size=0
14 bd_ptr=0xD918 pak=0x12C5D4 ds=0xE5760C status=80 pak_size=0
15 bd_ptr=0xD92C pak=0x12C828 ds=0xE57CC8 status=80 pak_size=0
16 bd_ptr=0xD940 pak=0x12CA7C ds=0xE58384 status=80 pak_size=0
cpb = 0xE4, eda = 0xE028, cda = 0xE028
TX ring with 4 entries at 0xE4E000
00 bd_ptr=0xE000 pak=0x000000 ds=0xE6FF38 status=80 pak_size=291
01 bd_ptr=0xE014 pak=0x000000 ds=0xE705F4 status=80 pak_size=291
02 bd_ptr=0xE028 pak=0x000000 ds=0xE6A098 status=80 pak_size=22
03 bd_ptr=0xE03C pak=0x000000 ds=0xE6F1C0 status=80 pak_size=291
04 bd_ptr=0xE050 pak=0x000000 ds=0xE6F87C status=80 pak_size=291
0 missed datagrams, 0 overruns
0 bad datagram encapsulations, 0 memory errors
0 transmitter underruns
0 residual bit errors

Code:

bottom#show interface ser 0
Serial0 is up, line protocol is up
  Hardware is HD64570
  Internet address is 192.168.57.2/24
  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)
  Last input 00:00:09, output 00:00:04, output hang never
  Last clearing of "show interface" counters never
  Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0
  Queueing strategy: fifo
  Output queue :0/40 (size/max)
  5 minute input rate 0 bits/sec, 0 packets/sec
  5 minute output rate 0 bits/sec, 0 packets/sec
     56 packets input, 1232 bytes, 0 no buffer
     Received 56 broadcasts, 0 runts, 0 giants, 0 throttles
     0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort
     136 packets output, 20227 bytes, 0 underruns
     0 output errors, 0 collisions, 37 interface resets
     0 output buffer failures, 0 output buffers swapped out
     42 carrier transitions
     DCD=up  DSR=up  DTR=up  RTS=up  CTS=up
bottom#

Would you mind explaining what you are looking for in the output of these commands? I think I know what your looking at in the first one, I'm not so sure with the second - if nothing else, this is turning into a good lesson in troubleshooting for me