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Slight configuration changes for 3G connectivity on new C887VAG+7

Purpose:

This is a short document to explain about the main configuration changes while migrating from the old 887G
router to the new C887VAG+7-K9.


Summary:

The new C887VAG+7 includes a MC8705 HSPA+ modem which requires some slight configuration changes
compared to
all previous 3G modems.

Symptoms:

1. It is not possible to configure ¨PPP encapsulation and the following error message is seen.

 

Router(config)#int cellular 0

Router(config-if)#encapsulation ppp

Cellular0: Only SLIP encapsulation supported


2. It is not possible to connect and get an IP address even when slip encapsulation is configured

Enabling "debug chat" you can see the following messages:

     Sep 19 15:42:40: CHAT3: Chat script gsm started
     Sep 19 15:42:40: CHAT3: Sending string: ATDT*98*1#
     Sep 19 15:42:40: CHAT3: Expecting string: CONNECT
     Sep 19 15:43:40: CHAT3: Timeout expecting: CONNECT
     Sep 19 15:43:40: CHAT3: Chat script gsm finished, status = Connection 
timed out; remote host not responding

Solutions:

1. The HSPA+R7 modem requires SLIP encapsulation.

In the new software architecture, on the data link between IOS and the modem itself, it supports IP data frames.

There are no SLIP frames but slip mode config is for legacy reasons only.

This is documented here:

http://www.cisco.com/en/US/docs/routers/access/1800/1861/software/feature/guide/mrwls_hspa.html#wp1527716

2. You also need a different chat script for this new modem.

     chat-script gsm "" "AT!SCACT=1,1" TIMEOUT 60 "OK"

This is documented here:

http://www.cisco.com/en/US/docs/routers/access/1800/1861/software/feature/guide/mrwls_hspa.html#wp1513906

Verification:

1. To check internet connectivity, you can ping the famous DNS Server which is always up and easy to remember

  ping 4.2.2.2

2. Check that the profile is active and that you got an ip address from the mobile wireless provider. The interface

should be up/up.

  show cellular 0 all

  show ip int brief

  show ip route

Contact the TAC:

If there is still some trouble to get a valid IP Address and connectivity through the 3G link, please raise a

new TAC case.

First make sure to enable millisecond (msec) timestamps using the  service timestamps command:

  Router(config)#service timestamps debug datetime msec

  Router(config)#service timestamps log datetime msec

Then disable console logging and increase the logging buffer size to 4MB via

  Router(config)#no logging console

  Router(config)#logging buffer 4000000

Then enable the following debugs:

  debug chat

  debug dialer

and generate some traffic to trigger the dialer/cellular connection. If you don't see any debug, check to see

if you have a valid route through either the cellular 0 interface or corresponding dialer interface.

You can also try to reset the modem via:

  Router(config)#service internal 

  Router(config)#exit

  Router#test cellular 0 modem-power-cycle

Collect the following information

  show tech (includes running-configuration)

  show cellular 0 all

  show interface cellular 0

  show controller cellular 0

  show ip int brief

  show ip route

  show logs (to get the debugs output)

The collected output (show commands and debug) should provide enough information to determine what is

wrong with your configuration.

Comments
New Member

Hello, I followed the docummentation above, but I need ppp encapsulation and send an unsername/password through the cellular0 interface.

This is exactly my Hw

Cisco 887VAG2 (MPC8300) processor (revision 1.0)

Thank you in advance

Cisco Employee

Hi Pablo,

The HSPA+R7 modem requires SLIP encapsulation between IOS and the modem firmware. The PPP credentials to be used during the PDP Context establishment need to be configured while provisionning the modem via the 'cellular <> gsm profile create' CLI command.

Examples

The following example shows output for this command:

router# cellular 0/0/0 gsm profile create 3 apn.com chap gsm gsmPassword

Profile 3 will be created with the following values:

APN = apn.com

Authentication = CHAP

Username = gsm

Password = gsmPassword

Are you sure? [confirm]y

Profile 3 written to modem

More information on

http://www.cisco.com/en/US/docs/routers/access/1800/1861/software/feature/guide/mrwls_hspa.html#wp1240350

This is not related to the encapsulation used for the communication between IOS and the modem firmware.

Cheers,

Jean

New Member

Hi ,

I am using EHWIC HSPA+R7 module for Cisco 2901 but encountered the following error after configuration.

Can u advise and help?

Thanks

Paul Au

Nov 17 04:54:36.243: %LINK-3-BADENCAP: Interface Cellular0/0/0, Bad encapsulation code (30) -Process= "Exec", ipl= 0, pid= 3

-Traceback= 22B7F5E8z 225F6398z 22B5DE9Cz 22B5F028z 22B5F338z 22B5F3A4z 22EC67F4

z 22BA1EB8z 22BA29A4z 22BA36C0z 22BA3B00z 22BA7420z 2248D858z 2248D9FCz 22B332D8

z 2248C668z

Cisco Employee

Hi Paul,

This is a software defect, very likely this one which is not yet fixed :

CSCud20944

Traceback seen when trying to ping after FW upgrade: EHWIC-A, c3945e

Internally found moderate (Sev3) bug: A-Assigned

You should raise a TAC service request to confirm

Cheers,

Jean

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