Home > IT Answers > Networking > Our small company’s new IT purchase was a Cisco 1721 router to be connected to 4 ports from our DSU/CSU T1 line. Currently we use a cable modem connection but I am trying to establish a second connection that users could take advantage of as well. My
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 Our small company’s new IT purchase was a Cisco 1721 router to be connected to 4 ports from our DSU/CSU T1 line. Currently we use a cable modem connection but I am trying to establish a second connection that users could take advantage of as well. My
Networking Equipment, Routers
Allright, I have connection now to the 1721 router. I had one setting to change. I keep reading about all of these ISDN and frame/relay settings for the 1721. All I want to do is convert the t-1 csu/dsu serial internet connection to an ethernet signal to be interpretted by a desktop as an internet signal. I have all kinds of IP addresses from the t-1 provider. Here is the IP information they provided me to setup our network. Serial IP Block: xxx.49.195.24/30 * Customer WAN IP: xxx.49.195.26 * WAN Subnet Mask: 255.255.255.252 * WAN Gateway Address xxx.49.195.25 Ethernet IP block: xxx.132.236.88/29 * Ethernet Gateway Address: xxx.132.236.89 * Ethernet Subnet Mask: 255.255.255.248 * Customer Ethernet IP range: xxx.132.236.90 - xxx.132.236.94 Is my next step to try and program the IP addresses in the router? The router will have two IP addresses right? One for the WIC serial card and one for the Ethernet connection?

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ASKED: October 7, 2004  3:26 PM
UPDATED: October 8, 2004  2:02 PM
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Yes... You need to configure the wan interface with the wan IP provided (forget the wan ip block etc - all you need is IP address, gateway info and subnet mask. Then configure the ethernet interface with an ip from the address block they gave you; I'd have to check the exact procedure for enabling the communication on the 17xx router, but make sure you don't forget to bring up both interfaces and you should be golden. I would plug the router into some type of firewall/dhcp device, and assign private ips to the end user machines, nat'd by the firewall. then forwarded to the router. hope this is somewhat helpful
Last Wiki Answer Submitted:  October 8, 2004  10:03 am  by  NetServ1   0 pts.
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The 1721 settings are as follows.
FastEthernet0 ip address xxx.132.236.90
Serial0 ip address yyy.49.195.26
and I have the workstation nic card programmed ip address xxx.132.236.91

Are these the right settings from what our t-1 dealer provided me?

I can ping back and forth from the Fastethernet ip to the workstation nic ip. That is the only connection I can seem to receive.
When I use the Show Interfaces Serial command I am getting 1500 Framing errors.

Here is the IP information they provided me to setup our network.

Serial IP Block: yyy.49.195.24/30
* Customer WAN IP: yyy.49.195.26
* WAN Subnet Mask: 255.255.255.252
* WAN Gateway Address yyy.49.195.25

Ethernet IP block: xxx.132.236.88/29
* Ethernet Gateway Address: xxx.132.236.89
* Ethernet Subnet Mask: 255.255.255.248
* Customer Ethernet IP range: xxx.132.236.90 – xxx.132.236.94

I will eventually use this connection in an ISA Server but right now am just trying to acquire the internet signal for the first time.

Thanks.

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