Something I don’t see and don’t do very often is the configuration of a router including a 3G connection. So this blog post helps me during the process of configuring future connections. For todays configuration I am using the Dutch carrier KPN to establish the 3G connection. As hardware I am using a Cisco 888G router with a PCEX-3G-HSPA-G module. The most difficult during the configuration is the retrieval of the correct provider information. For this KPN connection is used the following credentials:

• – APN name: fastinternet
• – PPP CHAP username: <empty>
• – PPP CHAP password: <empty>
• – DNS: ns1.kpn-gprs.nl (62.133.126.28) & ns2.kpn-gprs.nl (62.133.126.29)

Don’t forget to use the above DNS servers when using a 3G connection from KPN. All other DNS servers, including Google’s DNS servers, won’t work.

The SIM card is locked by default with a password, so I first needed to unlock the SIM card. The unlocking of the SIM is accomplished with the following command:

router#cellular 0 gsm sim unlock <pin code>

The next thing to do is creating a gsm modem profile. With the modem profile you can configure different profiles with different APN, authentication, username and password combinations. For my connection I only need to specify the APN name, like shown below:

router#cellular 0 gsm profile create 1 fastinternet

Another important step is the configuration of a chat-script. The chat-script is used to define the Attention Dial Tone (ATDT) commands when the dialer is initiated. For gsm connections, the script always has the following syntax:

router(config)#chat-script <script name> “” “ATDT*99*<modem profile number>#” TIMEOUT <timeout value> CONNECT

Getting back to my configuration I configured the following chat-script:

router(config)#chat-script gsm-chat-script “” “ATDT*99*1#” TIMEOUT 30 “CONNECT”

Next you need to configure regular dial-on-demand (DDR) routing for the cellular interface. My cellular interface is used as the primary internet connection, so I included the necessary NAT statements on the interfaces.

interface Cellular0
no ip address
no ip redirects
no ip unreachables
no ip proxy-arp
ip nat outside
ip virtual-reassembly in
encapsulation ppp
dialer in-band
dialer pool-member 1
async mode interactive

!
interface Dialer1
ip address negotiated
ip nat outside
ip virtual-reassembly in
encapsulation ppp
dialer pool 1
dialer idle-timeout 0
dialer string gsm-chat-script
dialer persistent
ppp chap hostname <APN name>
ppp chap password 0 <provider password>
ppp ipcp dns request
no cdp enable

!
dialer-list 1 protocol ip permit

The last two steps involve the configuration of a default route and line configuration mode. I configure a regular default route with the Dialer 1 interface as next-hop interface. The line configuration mode, includes the following commands for the KPN connection.

line 3
script dialer gsm-chat-script
modem InOut
no exec
rxspeed 7200000
txspeed 5760000

That’s it. Just configure a routed or VLAN interface. Some NAT and ACL statements and you are ready to go. You can use several

show cellular 0 <commands>

commands for troubleshooting or information about your connection.

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René Jorissen

Co-owner and Solution Specialist at 4IP Solutions

René Jorissen works as Solution Specialist for 4IP in the Netherlands. Network Infrastructures are the primary focus. René works with equipment of multiple vendors, like Cisco, Aruba Networks, FortiNet, HP Networking, Juniper Networks, RSA SecurID, AeroHive, Microsoft and many more. René is Aruba Certified Edge Expert (ACEX #26), Aruba Certified Mobility Expert (ACMX #438), Aruba Certified ClearPass Expert (ACCX #725), Aruba Certified Design Expert (ACDX #760), CCNP R&S, FCNSP and Certified Ethical Hacker (CEF) certified. You can follow René on Twitter and LinkedIn.

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