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New Member

Connectivity over ISDN routers

Hi,My problem is very strange. At our central location we have a 2811 router having 2 ISDN lines on BRI 1/0 & 1/2. At 10 remote locations, we have 1721 router each loca with ISDN BRI connection. All router are connected to switches which contain the link to a LOCAL LAN network.

The main router ip is while the remote location router ip is like 10.2.x.1 . The machines under the LAN carry IP like 10.2.x.n (n=2-254

From a telnet session to I am able to ping remote router . However, I am not able to ping to any PC on the LAN behind the router. The same problem persist from each remote location.

We are using only STATIC IPs & no EIGRP. Do I need to introduce EIGRP in the config. ?


Re: Connectivity over ISDN routers

Do you have static routes configured on each end (hub and spoke) for each other's lan ? Also check the default gateway configurations to verify if they are properly set.

Static routes does not scale well, even though they work great for you if the number of sites are small. Running a protocol such as EIGRP or OSPF will help reduce the administrative overhead in maintaing routes in each router.

Since each remote office has only one isdn connection which dials to the hub site, i would suggest that you run default route ( from each remote to the hub site and spoke 1 will talk to spoke 2 through the hub. This default route can be statically configured or dynamically injected into EIGRP or OSPF. When you configure OSPF you do want to configure the ISDN circuit as DEmand circuit so that you do not waste valuable ISDN time = money..

If using EIGRP you will have to configure an ACL / Dialer list so that you deny eigrp packets in the ACL so that it doesnt trigger the link using hello packets.



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Re: Connectivity over ISDN routers


I am not sure if introducing a dynamic routing protocol will solve your issue. Can you post the full configurations of your main and one of the hub routers ?



New Member

Re: Connectivity over ISDN routers

If EIGRP configuration is set in the router configs whether we still require to config static ip router or that can be avoided ? Also, if both EIGRP & static route is set, wont it lead direct connectivity between 2 spokes bypassing the hub; We want only DDR to save time & money; How to set Dialer lists ?

Thanks for the early reply

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