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Multiple BRI's Dialing a PRI

I have a network that basically consists of two data centers and multiple access sites. The primary connection for the access sites is a frame relay network. If the frame relay connectivity fails, floating static routes are used to initiate an ISDN (BRI) connection to one of the data centers (PRI), if the initial attempt fails, it attempts to connect to the second data center. I am currently just using dial strings to determine the order in which each data center is dialed. If there are available channels, I would like all of the sites to connect to the primary data center and only use the secondary data center if the primary has reached capacity.

At one point, I had six access sites attempt to dial the same data center basically at the same time. All of the sites were setup to dial the primary data center first and then attempt the secondary data center. Five sites successfully connected to the primary, but one connected to the secondary.

1) Is there a limit on the number of connection attempts that a PRI can handle at one time?

There is the possibility that 20+ sites would attempt to connect at the same time.

2) Is the 'redial' command the most effective way to have all 20+ sites make the best-effort to try and connect the primary data center first and then attempt the secondary data center?

The data centers are using Cisco 3662's and the access sites use Cisco 2610's.

Thanks for your help!

1 REPLY
Cisco Employee

Re: Multiple BRI's Dialing a PRI

T1/PRI can handle 23 isdn calls at given time as its has 23B channels So calling from 6 nos of 2610 routers using bri line will be max 6x2=12 chans (i assume max one bri line at each site)

Now the best way to manage connecting primary server all the time is configuring order of dialer string in the config..Router will always try the first dialer string to initiate call if it can't connect at ISDN layer it will dial the next dialer string.

So if the 6th site can't connect to primary then we need to know the debug for

debug isdn q931

debug ppp negotiation

debug ppp authentication

debug dialer

term mon

from that site with bri config too...Thanks..Tejal

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