3845 T3 Module Question

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Jul 31st, 2008
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We have a 3845 that currently has 1 NM-1A-T3 and 1 NM-1T3/E3.

These are working circuits.

We are looking to replace these circuits with 1 DS3 to an MPLS carrier on a new 1 NM-1T3/E3 module.

We can install the module and configure the controller and the interface, but could not get the circuit to come into up up status.

There is a period of time (about 2 weeks) where we want to bring up the new DS3 and let it bake in, before rerouting traffic from the ATM and existing DS3 over it. At this time we will shutdown the ATM and existing DS3.

We have been told that the 3845 only supports 2 T3 modules.

The question we have though, is this a physical hardware limitation, in that we will never be able to have 3 working DS3s on a 3845, or is this a matter of performance i.e. we can have three configured and working DS3s on a 3845, just we will not get DS3 throughput.

We can live with the throughput, as the ATM DS3 only has a 4Mbps PVC configured, the existing DS3 is less than 50% utilized and the new DS3 will have no traffic on it until we migrate.

Any advice is appreciated.

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m-haddad Thu, 07/31/2008 - 08:41
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From the hardware perspective you can have the above NMs installed all together in the same router. However, not all IOS versions are compatible with t he above configuration. What IOS version are you running?


amstill Thu, 07/31/2008 - 08:49
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We have all the modules installed. 2 are already in production and working. The 3rd one we can configure both the controller and the interface, but the circuit would not come up. We are troubleshooting this from a circuit perspective, but in the meantime we are looking for a definitive answer as to whether this router can physically support 3 DS3's, or whether it is just a throughput issue.

m-haddad Thu, 07/31/2008 - 09:01
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The router can support the 3 DS3 circuits. The router will be able to handle the thoughput if you don't enable lots of features or run dynamic routing with big routing tables.

What feature set is your IOS? Advanced IP services?


Danilo Dy Thu, 07/31/2008 - 21:20
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The router can support these 3 modules. Since the two modules is up/up, I don't think its a problem with the IOS.

Since the third line is new, have you tried the third module and the third line in a separate router (maybe loan a router from your vendor for testing)? This is to make sure its not a line or module problem. I have experience "similar" in ds3/7500 router and the problem is at telco side, I can't remember the reason as its many years back - one reason could be loopback, when telco install the line they put it in loopback mode to test, they may have forgot about it before handing over to you.



amstill Fri, 08/01/2008 - 04:15
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Thanks for the replies. The circuit is good. We tested this first on a different router and ruled out telco.

Module is good - we shutdown one of the other circuits on this router and brought up the new circuit ok.

This same condition is repeatable on another 3845 in a different office.

So, the answer to my question is that the 3845 can only have a maximum of 2 T3s installed (no matter whether ATM or serial). Even though the 3rd module is recognised, configurable and does not show any errors on boot.

tdrais Fri, 08/01/2008 - 04:28
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Thanks for posting your findings. This is rather disturbing since I tend to use the same upgrade method you do. Other than capacity I have not seen a documented restriction on card configuration. This makes me wonder if there are other card combinations that won't really work.

Danilo Dy Fri, 08/01/2008 - 07:57
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This doesn't show in the configurator. Thanks for posting your observation.

As for me, I'm now using MetroE because ATM throughput is lower. i.e. for DS3/AAL5 its only 82%.

m-haddad Fri, 08/01/2008 - 08:22
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I did check the configuration tool and it doesn't say that the modules are not supported. As I mentioned below, many IOS version won't work with this configuration. I advise if you can check the IOS feature set that you are using against the configuration tool to see what are the versions that support this. If the card is recognized by the IOS it doesn't mean it is going to work.



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