Back to Back Routers

[alhaj]

Hi Everyone!
What Iam trying to do is to connect two routers via serial ports. I followed instructions from cisco..

http://www.cisco.com/warp/public/116/hdlc_back.html

I did everything the way they said but the connection does not stay up. Right when I finish configuring the the second router and I issue a no shutdown command to s0, the 2 routers will communicate for like 30 seconds and then the connection goes down. Here are the configs for both routers.
RouterA#sho run
Current configuration : 499 bytes
!
version 12.1
no service single-slot-reload-enable
service timestamps debug uptime
service timestamps log uptime
no service password-encryption
!
hostname Router
!
!
!
ip subnet-zero
!
!
!
!
interface Ethernet0
no ip address
shutdown
!
interface Ethernet1
no ip address
shutdown
!
interface Serial0
ip address 172.16.0.1 255.255.0.0
clock rate 64000
no cdp enable
!
interface Serial1
no ip address
shutdown
!
ip classless
ip http server
!
!
line con 0
line aux 0
line vty 0 4
!
end

RouterA#sho in s0
Serial0 is up, line protocol is down
Hardware is HD64570
Internet address is 172.16.0.1/16
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 never, output 00:00:07, output hang never
Last clearing of "show interface" counters 00:32:02
Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0
Queueing strategy: weighted fair
Output queue: 0/1000/64/0 (size/max total/threshold/drops)
Conversations 0/1/256 (active/max active/max total)
Reserved Conversations 0/0 (allocated/max allocated)
5 minute input rate 0 bits/sec, 0 packets/sec
5 minute output rate 0 bits/sec, 0 packets/sec
0 packets input, 0 bytes, 0 no buffer
Received 0 broadcasts, 0 runts, 0 giants, 0 throttles
14 input errors, 14 CRC, 0 frame, 0 overrun, 0 ignored, 13 abort
113 packets output, 2486 bytes, 0 underruns
0 output errors, 0 collisions, 64 interface resets
0 output buffer failures, 0 output buffers swapped out
61 carrier transitions

RouterB#sho run

Current configuration : 420 bytes
!
version 12.2
service timestamps debug datetime msec
service timestamps log datetime msec
no service password-encryption
!
hostname Router
!
!
ip subnet-zero
!
!
!
!
interface Ethernet0
no ip address
shutdown
!
interface Serial0
ip address 172.16.0.3 255.255.0.0
no fair-queue
no ip address
shutdown
!
interface Serial0
ip address 172.16.0.3 255.255.0.0
no fair-queue
no cdp enable
!
interface Serial1
no ip address
shutdown
!
ip classless
ip http server
!
!
!
line con 0
line aux 0
line vty 0 4
!
end

RouterB#sho in s0
Router#sho in s0
Serial0 is up, line protocol is down
Hardware is HD64570
Internet address is 172.16.0.3/16
MTU 1500 bytes, BW 1544 Kbit, DLY 20000 usec,
reliability 179/255, txload 1/255, rxload 1/255
Encapsulation HDLC, loopback not set
Keepalive set (10 sec)
Last input never, output 00:00:01, output hang never
Last clearing of "show interface" counters 00:25:25
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
0 packets input, 0 bytes, 0 no buffer
Received 0 broadcasts, 0 runts, 0 giants, 0 throttles
109 input errors, 109 CRC, 8 frame, 0 overrun, 0 ignored, 90 abort
161 packets output, 4395 bytes, 0 underruns
0 output errors, 0 collisions, 21 interface resets
0 output buffer failures, 0 output buffers swapped out
78 carrier transitions
DCD=up DSR=up DTR=up RTS=up CTS=up

This is what I get when I issue the last command on RouterB.

RouterB(config-if)#no shut
RouterB(config)#
*Mar 1 00:18:35.295: %LINK-3-UPDOWN: Interface Serial0, changed state to up
*Mar 1 00:18:36.299: %LINEPROTO-5-UPDOWN: Line protocol on Interface Serial0, changed state to up
Router(config)#
*Mar 1 00:19:02.723: %LINEPROTO-5-UPDOWN: Line protocol on Interface Serial0, changed state to down

**Notice the time

Thanks for any suggestions. And sorry for the long question but this was the only way to explain in detail.

 

[cyberspew]

you have ALOT of extra lines in your running config I would 1st erase the running config and try programming it from scratch another thing I would try is setting clock rate on both side (yes I know its not required BUT I always do it to be on the safe side) last thing I have never set my serial interfaces above 56000 if cisco says to do it I guess it should work but I would try reducing it maybe the extra speed is causing an unstable link (just a random thought)

Thanks
Jason

 

[alhaj]

Thanks, I tried the slower clock rate but it still goes out after about 30 seconds. Plus you can only set clock rate on the DCE side.

I tried debug serial interface, this is what I got.

04:24:04: HD(0): New serial state = 0x0600

04:24:04: HD(0): Cable is unplugged.
04:24:04: HD(1): got an interrupt state = 0x8455
04:24:04: HD(1): New serial state = 0x0455

04:24:04: HD(1): DTR is down.
04:24:04: HD(0): New serial state = 0x0600

04:24:04: HD(0): Cable is unplugged.
04:24:04: HD(1): got an interrupt state = 0x845F
04:24:04: HD(1): New serial state = 0x045F

The cables are brand new and theyre not unplugged.

 

[ccie9545]

That is true you only set the clockrate on the DCE side of the connection. You might want to check to make sure that the DCE end of the cable is actually plugged into the router with the clockrate configured.

I believe in this case the HD is referring to the Serial Controller or referring to the High Density V.35 cable. The debug output shows that only Serial0 cable is unplugged, do you have the cable plugged into Serial0 or into Serial1? If it is plugged into serial1 then move it to serial0.

If it is plugged into serial0, you might want try moving it to serial1 and configuring serial1 to see if that works. If serial1 works you could have a bad interface.

Plus, there are some cable types that require you to set or remove jumpers to determine the DCE and DTE side, if i remember correctly. What type of cable are you using?

What is the output when you do a show controllers? Erik Rudnick, CCIE No. 9545
mailto:erik@kuriosity.com

 

[alhaj]

Hi Erik,

RouterA#sho cont se 1
HD unit 1, idb = 0x1197DC, driver structure at 0x11FB68
buffer size 1524 HD unit 1, RS-232 DCE cable
cpb = 0x23, eda = 0x940, cda = 0x800
RX ring with 16 entries at 0x230800

RouterB#sho cont se 1
HD unit 1, idb = 0x1E0D28, driver structure at 0x1E8388
buffer size 1524 HD unit 1, RS-530 DTE cable
cpb = 0x2, eda = 0x3140, cda = 0x3000
RX ring with 16 entries at 0x4023000

I switched terminals on both routers and it still does the same thing. Theyre no jumpers on the cable.
I get the same errors on both routers.

*Mar 1 00:11:22.839: HD(0): Cable is unplugged.

 

[routerjunky]

Cable standards mismatch. One cable is RS-232 DCE the other is RS-530 DTE. You will need to procure either a RS-232 DTE or a RS-530 DCE.

 

[alhaj]

Thanks routerjunky and ccie
I didnt think that it made a difference. Ill see if i can swap the pins to make it work.

 

[ccie9545]

cables...such a hassle... Erik Rudnick, CCIE No. 9545
mailto:erik@kuriosity.com

 

[tattl]

Maybee I overlooked something, but I didn't see a bandwidth statement on the serial interface for Router B....

 

[alhaj]

Thanks everyone for the help, it was the cable. I went and bought a RS-232 DTE cable and now the connection stays up.

 

[ladyvstar]

Correct me if I'm wrong here ccie9545, but alhaj, if you would have noticed the number of crc errors and carrier transitions in the show int s0 statement, that should have also been a tailtale sign that it could have been a cableing issue.

Glad to hear that you got it figured out...

 

[alhaj]

Cant blame me on that one, Iam just learning.

 

[routerjunky]

Tattl - The bandwidth statement is not required nor does it affect the serial interface. The bandwidth command sets the bandwidth metric component for routing protocols which use it in its caculation.

Programs using SNMP also use the bandwidth command. By default the BW of a serial interface is 1544 Kbit. SNMP programs would make its calculations based on this value.

In the configs presented here you can see the clock is 64000, since there is no BW command SNMP data collocted would not accurately represent what is happening on this link.