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Response Problems 1603 FW Channel Bonded ISDN

We are seeking any help/suggestions regarding poor response of a recently installed a 1603 with F/W feature set, using Channel Bonded ISDN for connection to an ISP.

Generally functionality seems OK but the client is complaining of periods of very poor response. To monitor this we ran a ping monitor problem on a client computer, pinging the ISP's primary DNS server every 30 secs or so for a full day.

The results, integrated with the router syslog, showed that the primary channel remained connected almost all the time - except as explained further below - which is what we would expect due to the 'ping' traffic. The secondary channel cut in and cut out presumbly according to the load experienced.

At times the ping response went right out (I guess timed out) and on most occasions this continued until the primary channel dropped and reconnected. It was interesting to note that the period during which these timeouts were occurring and before the router dropped the connection was remarkably constant between 7 and 8 minutes)

The router dialer timeout is set to only 2 minutes.

The ISP claims that its timeout does not operate reliably (if at all and anyway it is 5 minutes) The ISP was unaware of any particular problems at the time.

We do get apparently good packets being rejected by CBAC (see my other post) but none of these occur during the periods in question.

I have seen a comment about a bad PIX NAT configuration causing intermittant lack of routing so I am kind of wondering whether this is a possible problem. However the NAT config is fairly simple - using a single IP address in the global pool with a single overload on port 25 for one host (for incoming SMTP traffic).

Any suggestions gratefully received.


Re: Response Problems 1603 FW Channel Bonded ISDN

Often times complex troubleshooting issues are best addressed in an interactive session with one of our trained technical assistance engineers. While other forum users may be able to help, it’s often difficult to do so for this type of issue.

To utilize the resources at our Technical Assistance Center, please visit and to open a case with one of our TAC engineers, visit

If anyone else in the forum has some advice, please reply to this thread.

Thank you for posting.

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