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Beginner

Problem with serial port extender via IP (async line)

Hi all!

I have created seral port extender over IP based on Cisco 28xx routers and HWIC-1T + CAB-SS-232FC/MT cables pair.

Here is a picture of my network setup

BSTUN protocol is used in asynchronous mode (yes, I need async). I took this Cisco's sample https://www.cisco.com/c/en/us/support/docs/ip/serial-tunnel-stun/41983-bstun-41983.html and applied to my routers. Both routers in the same LAN, connected to the same unmanaged switch. Each interface can ping each other. So, no any IP connectivity/latency/packet loss problems at all.

My config part related to this "extender" looks like this:

bstun peer-name 192.168.168.145

bstun protocol-group 103 async-generic

!

interface loopback1

ip address 192.168.168.145 255.255.255.255

!

interface serial 0/2/0

physical-layer async

encapsulation bstun

asp role secondary

bstun group 103

bstun route all tcp 192.168.168.146

!

line34

modem DTR-active

speed 9600
< routing part omitted >

bstun peer-name 192.168.168.146

bstun protocol-group 103 async-generic

!

interface loopback1

ip address 192.168.168.146 255.255.255.255

!

interface serial 0/2/0

physical-layer async

encapsulation bstun

asp role primary

bstun group 103

bstun route all tcp 192.168.168.145

!

line34

modem DTR-active

speed 9600

< routing part omitted >

I got working terminal to terminal "messaging" at 9600 bps, and one of serial apps works well too. But most of serial applications (which are 9600 async too!) fails via this serial "extender". I tried many apps, that works absolutely stable on real COM ports and tried many, 5 as minimum. And they are all fails - they try to communicate, send some data, but finally shows timeout, error or doesn't do what expected on the remote side.

I started investigating in direction of commands used to configure such kind lf lines. I read a lot about serial troubleshooting. And I've tried to issue every found command step by step (with checking result after each command issue). But no luck. Here is a list of commands I've applied to ascyn line 34 (s0/2/0):

speed 9600
stopbits 1
databits 8
flowcontrol none | software | hardware
parity none
no motd-banner
no exec-banner
no vacant-message
exec-timeout 0 0
no flush-at-activation
special-character-bits 8
transport input all
transport output all
escape-character none | break | default
modem inout
exec | no exec
no activation-character
session-timeout 0

No luck.

 

After that I started doing serial port sniffing (by using MS PORTMON) to find dfferencies in data exchange via local COM port and network COM port. And I found a reason in a second! Because all of IRP_MJ_READ request has TIMEOUT status instead of SUCCESS (when local serial port used). And also request length is zero (no data) instead of useful data. Here are portions of PORTMON logs from different setups:

Cisco serial extension

Local com port

19            0.00003131             IRP_MJ_WRITE      Serial0                SUCCESS Length 1: F0           

20            0.00000411                IOCTL_SERIAL_GET_COMMSTATUS     Serial0                SUCCESS                

21            0.04243267             IRP_MJ_READ        Serial0                SUCCESS Length 1: F0           

22            0.00002310             IRP_MJ_WRITE      Serial0                SUCCESS Length 1: 02           

23            0.00000359                IOCTL_SERIAL_GET_COMMSTATUS     Serial0                SUCCESS                

24            0.04407666             IRP_MJ_READ        Serial0                SUCCESS Length 1: 02           

25            0.00004157             IRP_MJ_WRITE      Serial0                SUCCESS Length 1: 00           

26            0.00000411                IOCTL_SERIAL_GET_COMMSTATUS     Serial0                SUCCESS                

27            0.04361267             IRP_MJ_READ        Serial0                SUCCESS Length 1: 00           

28            0.00003952             IRP_MJ_WRITE      Serial0                SUCCESS Length 1: F2           

29            0.00000308                IOCTL_SERIAL_GET_COMMSTATUS     Serial0                SUCCESS                

30            0.04404176             IRP_MJ_READ        Serial0                SUCCESS Length 1: F2           

31            0.00000308                IOCTL_SERIAL_GET_COMMSTATUS     Serial0                SUCCESS                

32            0.05498560             IRP_MJ_READ        Serial0                TIMEOUT Length 0:                

33            0.00000359                IOCTL_SERIAL_GET_COMMSTATUS     Serial0                SUCCESS                

34            0.05494403             IRP_MJ_READ        Serial0                TIMEOUT Length 0:                

35            0.00000411                IOCTL_SERIAL_GET_COMMSTATUS     Serial0                SUCCESS                

36            0.05492658             IRP_MJ_READ        Serial0                TIMEOUT Length 0:                

37            0.00000359                IOCTL_SERIAL_GET_COMMSTATUS     Serial0                SUCCESS                

38            0.05493582             IRP_MJ_READ        Serial0                TIMEOUT Length 0:                

39            0.00000411                IOCTL_SERIAL_GET_COMMSTATUS     Serial0                SUCCESS                

40            0.05493274             IRP_MJ_READ        Serial0                TIMEOUT Length 0:                

41            0.00000359                IOCTL_SERIAL_GET_COMMSTATUS     Serial0                SUCCESS                

19            0.00003028             IRP_MJ_WRITE      Serial0                SUCCESS Length 1: F0           

20            0.00000308                IOCTL_SERIAL_GET_COMMSTATUS     Serial0                SUCCESS                

21            0.00553711             IRP_MJ_READ        Serial0                SUCCESS Length 1: F0           

22            0.00002772             IRP_MJ_WRITE      Serial0                SUCCESS Length 1: 02           

23            0.00000411                IOCTL_SERIAL_GET_COMMSTATUS     Serial0                SUCCESS                

24            0.00545858             IRP_MJ_READ        Serial0                SUCCESS Length 1: 02           

25            0.00002669             IRP_MJ_WRITE      Serial0                SUCCESS Length 1: 00           

26            0.00000359                IOCTL_SERIAL_GET_COMMSTATUS     Serial0                SUCCESS                

27            0.00548219             IRP_MJ_READ        Serial0                SUCCESS Length 1: 00           

28            0.00002926             IRP_MJ_WRITE      Serial0                SUCCESS Length 1: F2           

29            0.00000411                IOCTL_SERIAL_GET_COMMSTATUS     Serial0                SUCCESS                

30            0.01288655             IRP_MJ_READ        Serial0                SUCCESS Length 1: F2           

31            0.00000257                IOCTL_SERIAL_GET_COMMSTATUS     Serial0                SUCCESS                

32            0.00000257             IRP_MJ_READ        Serial0                SUCCESS Length 1: F0           

33            0.00000205                IOCTL_SERIAL_GET_COMMSTATUS     Serial0                SUCCESS                

34            0.00000205             IRP_MJ_READ        Serial0                SUCCESS Length 1: 03           

35            0.00000205                IOCTL_SERIAL_GET_COMMSTATUS     Serial0                SUCCESS                

36            0.00000205             IRP_MJ_READ        Serial0                SUCCESS Length 1: 01           

37            0.00000154                IOCTL_SERIAL_GET_COMMSTATUS     Serial0                SUCCESS                

38            0.00000205             IRP_MJ_READ        Serial0                SUCCESS Length 1: 53           

39            0.00000205                IOCTL_SERIAL_GET_COMMSTATUS     Serial0                SUCCESS                

40            0.00000257             IRP_MJ_READ        Serial0                SUCCESS Length 1: 47           

41            0.00002053             IRP_MJ_WRITE      Serial0                SUCCESS Length 1: F0           

I believe that there is a some setting/trick in Cisco, because all of my serial apps works fine via Moxa NPorts serial-to-Ethernet adapters (they are async only). With no any manual settings, just IP settings and everything works fine.

But I need to run Cisco.

Any ideas, guys?

10 REPLIES 10
VIP Mentor

Re: Problem with serial port extender via IP (async line)

Hello,

 

not sure if this is in any way helpful, but what if you use UDPTN as the transport ?

 

https://www.cisco.com/c/en/us/td/docs/ios/12_2/dial/configuration/guide/fdial_c/dafudptn.pdf

Beginner

Re: Problem with serial port extender via IP (async line)

Hi Georg! Why not? But what encapsulations you see for UDPTN?

interface serial 0/2/0

physical-layer async

no ip address

encapsulation ?

clock rate 9600

shut

no shut

exit

!

line 0/2/0

speed 9600

no session-timeout

transport output udptn

dispatch-timeout 10000

dispatch-character 13

modem in

autocommand udptn 192.168.1.144

interface serial 0/2/0

physical-layer async

no ip address

encapsulation ?

shut

no shut

exit

!

!

line 0/2/0

speed 9600

no session-timeout

transport output udptn

dispatch-timeout 10000

dispatch-character 13

modem in

autocommand udptn 192.168.1.143

VIP Mentor

Re: Problem with serial port extender via IP (async line)

The encapsulation stays the same, you just change the transport protocol under the line config. The document I linked to provides a few samples...

Beginner

Re: Problem with serial port extender via IP (async line)

Of course I took config example from PDF you provided. I chosen P2P option, because it fit my application (from description). Unfortunately, that's file has nothing on serial interfaces configuration (this part is omitied at all for some reason). So, I have to set it by my own. But I am not a Cisco guru. For example, I am not sure what shall I do with these lines?

interface serial 0/2/0 -- this line remains unchanged
physical-layer async -- this line remains unchanged
encapsulation bstun -- this line remains unchanged
asp role ... -- but this line?
bstun group 103 -- but this line?
bstun route all tcp 192.168.168.x -- but this line?

Also I come across with this thing:

2811_2#udptn 192.168.1.143
% udptn connections not permitted from this terminal

 

VIP Mentor

Re: Problem with serial port extender via IP (async line)

Hello,

 

I think UDPTN is IOS and platform specific. The 2811 with 15.1.(3)T4 Advanced Enterprise Services supports it, as an example. Which IOS are you running ?

Beginner

Re: Problem with serial port extender via IP (async line)

I run:

2811_1# show ver
Cisco IOS Software, 2800 Software (C2800NM-ADVENTERPRISEK9-M), Version 15.1(4)M12a, RELEASE SOFTWARE (fc1)
...
ROM: System Bootstrap, Version 12.4(13r)T, RELEASE SOFTWARE (fc1)
VIP Mentor

Re: Problem with serial port extender via IP (async line)

Hello,

 

according to the feature navigator, your IOS version should support it. Try and enable 'service udp-small-servers' globally...

Beginner

Re: Problem with serial port extender via IP (async line)

Tried, but same error. How about to configure everyting else first? Like a few lines in serial interface with my notes? Maybe problem is there.

VIP Mentor

Re: Problem with serial port extender via IP (async line)

Hello,

 

I am getting the same error on anything in GNS3 and VIRL...weird.

 

I'll check if I can find some more info...

Beginner

Re: Problem with serial port extender via IP (async line)

Okay, thanks anyway.

Do you have other option ideas for async tunneling? I don't like UDP idea too much, maybe any other options available, based on TCP? SDLC or Frame Relay maybe?

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