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New Member

Translation of DIX / Ethernet II to 802.3

We have a seemingly unusual problem. We are migrating away from Token Ring, replacing it with switched Ethernet (all-Cisco network). In the process, we've hit a roadblock.

We have a legacy system attached via Ethernet that communicates (translational bridging) with the Token Ring interface into our mainframe (a 3745 TIC) via SNA. This legacy system can handle only the DIX / Ethernet II frame format. The mainframe also has an Ethernet connection, to which we've migrated all other SNA communications in an effort to eliminate the need for Token Ring equipment.

However, the mainframe understands SNA through Ethernet only over the 802.3 frame format (i.e., with the 802.2 LLC sublayer DSAP/SSAP fields). Thousands of our Ethernet-attached workstations are talking SNA just fine with the mainframe Ethernet adapter, using 802.3 Ethernet frame format, through transparent bridging. But the legacy system can't talk SNA with the mainframe Ethernet interface because the mainframe is looking for SNA via 802.3 while the legacy system can speak SNA only over DIX / Ethernet II.

This isn't a problem with the legacy system talking to the mainframe via Token Ring, because the DSAP and SSAP information in the legacy system Ethernet II frames are being repopulated into the correct Token Ring frame fields when they are translationally bridged to Token Ring.

It appears, then, that our challenge is translating the DIX / Ethernet II frames from the legacy system to 802.3 frames at some point in the transparent bridging path. So, the question: is there some reasonable way to tell an MSFC2 to translate DIX / Ethernet II frames coming in on one VLAN interface to 802.3? I haven't found anything obvious.

Thanks for any insight.

New Member

Re: Translation of DIX / Ethernet II to 802.3

I dont think so this is possible...


Re: Translation of DIX / Ethernet II to 802.3

You can create subinterfaces / secondary addresses (two different things) where one interface is EthernetII for TCP/IP, and the other is 802.3 with SAPs.

You'd then set up a static route for the Mainframe's address so that all traffic destined to the 'frame is sent out that interface.

Of course, you can (and should) acutally have atwo discreet interfaces, one for the 'frame, one for the rest of the network.

In the future you can (given a decent budget) add a CIP (Channel Interface Processor) to the router (it's got to be one of the "big" routers, like a 7XXX series). The CIP allows for channel attachment to the mainframe (or, maybe update the TIC in the 'frame to a more current flavor).

Good Luck