Document ID: 17603
Questions
Introduction
I have a multi-link PPP connection. I cannot get both channels to come up with my 3Com Impact TA. What should I do?
Does the Micro Router 900i support ISDN 2 B-Channels? Do I need a special cable or ISDN TA?
Do you have any recommendations on configurations for ISDN?
Would a MicroRouter 1000R/TA connection via the Ethernet port provide much better speed than the standard TA connection straight to the Macintosh serial port? Also, do I need to get two IP addresses from my ISP, one for the MR1000R's Ethernet port and one for the Macintosh?
What is the proper syntax in the chat script to tell the modem to dial two LDNs? I have two 64K ISDN lines, and I am using an Adtran ISU Express that is configured to use Bonding mode 1.
Related Information
Introduction
This document answers some of the most frequently asked questions about ISDN.
Refer to Cisco Technical Tips Conventions for more information on document conventions.
Q. I have a multi-link PPP connection. I cannot get both channels to come up with my 3Com Impact TA. What should I do?
A. If you are unable to bring the B-channel up in a multi-link PPP connection, first put S80=1 in the chat, this enables Multilink PPP even though it should be on by default. Then put S71=1 in the chat, this sets the B-channel protocol to Async-Sync conversion. Lastly, you must change the baud rate to 115200. Do this by entering the command $B115200.
Q. Does the Micro Router 900i support ISDN 2 B-Channels? Do I need a special cable or ISDN TA?
A. Yes, it supports up to 128 K synchronous data rate. You must use an ISDN terminal adapter (TA) with an RS-232 interface. The TA must be capable of bonding the 2 B channels together. The Adtran ISU 128 and ISU Express both work well, but they are somewhat more expensive than other ISDN TAs.
Q. Do you have any recommendations on configurations for ISDN?
A. See these references:
- Compatible Systems Tech Note Adtran ISU Express set-up
- Compatible Systems Tech Note Motorola Bitsurfer Pro set-up
Q. Would a MicroRouter 1000R/TA connection via the Ethernet port provide much better speed than the standard TA connection straight to the Macintosh serial port? Also, do I need to get two IP addresses from my ISP, one for the MR1000R's Ethernet port and one for the Macintosh?
A. The maximum data rate for the serial port is around 38,400 for most Macs. If you look at a 2B ISDN line, you would be better off with an Ethernet/WAN connection.
Yes, you would need two addresses and they need to be on the same net. However, the ISP may not give you just two.
Q. What is the proper syntax in the chat script to tell the modem to dial two LDNs? I have two 64K ISDN lines, and I am using an Adtran ISU Express that is configured to use Bonding mode 1.
A. The two LDNs are configured in the TA. The router does not need to do a thing. The Bonding protocol dials the first number and negotiates with the remote TA. If the remote TA is willing to do bonding, then a second call is established and the two channels are multiplexed together. Some ISDN switches require you to configure the TA with two different LDNs while others use the same number for both. Check with your ISDN service provider to be sure.
Related Information
| Updated: Apr 12, 2002 | Document ID: 17603 |