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10.26.2009

Configuring Simple Dialup ISP Connection using a Cisco Access Server

With high-speed Internet connections easily available, one would wonder why someone would want to use dialup Internet Service Provider (ISP) from a Cisco access server. I have recently become involved in a project that requires a dialup connection. It took me some time to get the configuration just right, so I thought it might be beneficial to others to post the config here.

Follow up:

This config is for an AS5400 Cisco Universal Access Server. In this scenario it is configured to utilize a T1 for access to the public telephone system and does not allow dialin connections.

Here are the pertinent config lines:

Code:

	`! Configure a dialer with one or more dial strings`
	`interface Dialer1`
	`ip address negotiated`
	`ip nat outside`
	`encapsulation ppp`
	`dialer pool 1`
	`dialer order round-robin`
	`dialer enable-timeout 3`
	`dialer string 3035550000`
	`dialer string 3035550001`
	`dialer-group 1`
	`no cdp enable`
	`ppp pap sent-username someuser@dialup.com password somepassword`
	`!`
	`! Configure a group of asynchronous interfaces`
	`interface Group-Async1`
	`ip unnumbered FastEthernet0/0`
	`ip nat inside`
	`encapsulation ppp`
	`dialer in-band`
	`dialer pool-member 1`
	`dialer idle-timeout 300`
	`async mode interactive`
	`ppp authentication chap pap callin`
	`group-range 2/56 2/57`
	`routing dynamic`
	`!`
	`! Create an access list for controlling what traffic is allowed`
	`access-list 101 remark ** Interesting traffic for Dialer 1 **`
	`access-list 101 permit tcp any any eq www`
	`access-list 101 permit tcp any any eq 443`
	`access-list 101 deny eigrp any any`
	`access-list 101 deny ip any any`
	`!`
	`!`
	`ip nat inside source list 101 interface Dialer1 overload`
	`!`
	`!`
	`dialer-list 1 protocol ip list 101`
	`!`
	`! Define a modem initialization string to use`
	`modemcap entry dialup-isp:MSC=&f`
	`!`
	`! Define a couple of lines/modems for use`
	`line 2/56 2/57`
	`no modem InOut`
	`modem autoconfigure type dialup-isp`
	`no exec`
	`transport preferred none`
	`transport input all`
	`transport output all`
	`autoselect during-login`
	`autoselect ppp`
	`!`
	`! Define a default route for Internet traffic to reach the dialer`
	`ip route 0.0.0.0 0.0.0.0 Dialer1`
	`!`

Multiple phone numbers for the ISP configured in the dialer interface allows the access server to use each one in round-robin order. Having more than one phone number also gives the access server more possibilities for a successful connection in the event a number is busy or out of service. Having two lines configured for use adds redundancy at the line/modem level in case one becomes bad is otherwise out of service.