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Community Member

45mb DS3 to ethernet conversion/Transparent bridging.

Hi All,

Just wanted some pointers, I need to implement a solution which requires a 45mb G.703 T3 full rate (DS3) circuit presented each end as Ethernet (layer 2). Plan is to terminate the serial DS3 circuit on two 3825's with the NM-1T3/E3 modules and transparently bridge the outside ethernet segments with queueing to sinulate a 45 mb ethernet layer 2 point to point to the outside routers.I have look at metrodata DS3/ethernet converters but they don't offer LLF and they queue/buffer indescriminately based on TCP based flows.


Does anyone have example config's for transparent bridging so that the two end routers will see the 45mb layer 2 ethernet link and not the two 45mb serial routers/circuit in between. Obviously CDP will be removed.

2) I have the queueing data for the 100mb/45mb reduction but has anyone played with LLF so that if the G.703 45mb central circuit is lost, the ios shuts down it's outside ethernet interfaces? I have been told to look at Embeeded Event Manager in IOS to perform such an operation, but looks extremely complicated using TCL scripts. Any other ideas?

Thanks Guys, Appreciated in Advance


Hall of Fame Super Gold

Re: 45mb DS3 to ethernet conversion/Transparent bridging.

1. normal bridging configuration. Why are you concerned about buffering ? The default should be fine.

2. is not that complicated, and seems to me the only method to do that.

Community Member

Re: 45mb DS3 to ethernet conversion/Transparent bridging.

Thanks for the reply,

1) just a concern over using Low latency applications queueing down from 100 to 45mb on the third party DS3/ethernet transceivers without queuing algoriths being present on such devices.

2) thanks for the confirmation, Just looked at the EEM v2 documentation and it does seem to track and act on interface state and snmp/log state changes. Just got to work it all out now.

Thanks for the sanity check, welcome any other feedback from others, will feedback.


Hall of Fame Super Gold

Re: 45mb DS3 to ethernet conversion/Transparent bridging.

Well, one problem is that with bridging, if you want to configure something like QoS / LLQ, you will find that is complicated (offset-based access list) and possibly unsupported. At some point, configuring some kind of L2 transport over IP could help.

Also a bit strange the necessity of shutting down the ethernet when ds3 is down, but I guess everything is non-standard in this design.

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