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DTC and Bridging

Timothy Pfeiff
Occasional Contributor

DTC and Bridging

We are in the process of upgrading WAN links for one of our customers. They currently have HP DTC at their remote locations that commmunicate to a central site that houses an HP 3000. The current network is using Cisco 2600/2500 routers at the remotes and a 3660 router at the central site. The 3660 and HP equipment are connected to a Cisco 4006 Catalyst switch. They currently have briding enabled on the existing WAN links as well as the required LAN segments and all works well. The new design has T1 lines connecting 2600 routers at the remotes to a 3640 router at the central site. The 3640 has been connected to the catalyst 4006 on the same subnet at the HP equipment and bridging has been turned on all the appropriate serial and lan interfaces. We see a few bridged packets from the DTC at the remote arrive at the 4006 switch as well as DTC packets from the central site arrive at the remote. We also see one packet from the HP 3000 arrive at the remote. We have confirmed that IEEE protocol is being used through out. When the old link is brought down and all bridge tables and cam tables are cleared, the DTC at the remote site will no longer operate correctly...ie...the cash drawers and printers will not respond. Again we see some bridged traffic from the appropriate DTC's and HP 3000 traversing the network but nothing more. We have rebooted the DTC and waited for up to an hour to see if it would download a new config without success. When we turn down the new WAN link and put the old one back online, the config downloads and all remote equipment works. We have checked our IOS versions with Cisco and even had Cisco engineers look at the configs of all the equipment without any resolution. Has anyone here seen anything similar?
Ron Kinner
Honored Contributor

Re: DTC and Bridging

I suppose you have verified that there is nothing funny going on in the switch such as different VLANs

Are you using any filtering on the bridges? If so did you allow for the hp multicast address 09-00-09-xx-xx-xx? If you haven't already I would add log to the end of each access list statement so you could see what is being permitted and denied.

Do you have access to the configs on the old routers? or do they belong to another company?

Are the IOS versions of the old routers a full number older than the new? 11.x vs 12.y? Sometimes the defaults change and bite you.

It doesn't really sound like you have router config problems tho. Perhaps there is something you have to do to the DTC to wake them up? You would probably have better luck if you post in the


The people who use DTCs mostly hang out in the mpe/ix forum. This networking forum is very new and doesn't have that many readers yet.

Timothy Pfeiff
Occasional Contributor

Re: DTC and Bridging

We've been careful to make sure we stay on the same segment as the HP equipment. The 3660 currently has 4 vlans across a fast ethernet trunk to the catalyst 4k. We directly connected the 3640 to the catalyst on the same vlan the the HP equipment is on. We have also tried connecting to the 3660 on a new segment and letting it route/bridge to the 4k for us along with the existing links. All the new equipment is running IOS 12.1 or higher. We have numerous other sites that bridge well with the versions of IOS and equipment we have deployed. To make sure I understand the communications for the HP...does the remote DTC communicate with the HP or with another DTC that is directly connected to the HP?
Thanks for your help!
Ron Kinner
Honored Contributor

Re: DTC and Bridging

I think the communication is from the 3000 to the DTC. You have to run a program called NMMGR
(Node Management Services Configuration Manager. A software subsystem
that enables you to configure DTC connectivity and network access
parameters for an HP 3000 Series 900 computer.)

on the 3000 to configure them. Then follow it up with a program called SYSGEN.

The config data is stored in:
(A file that contains all the network configuration data for the HP 3000
Series 900 computer on which it resides. It includes information about
the DTCs that can access the system as well as information about any
Network Services (NS) products running on the system. This is the only
file name allowed.)

The following post is sort of a general overview.


I'm not an expert on the things. Just read about them out of curiosity.

Also found this at:


"I believe the HP PROBE support you are looking for is enabled via the 'ARP
PROBE' command which is executed against an interface."

Based on the above I looked at the Cisco site and found this which looks like it would negatively impact you if your IOS is too new:


says the hp probe has been removed from 12.2(13)T.

I suppose because there is now a routable DTC they don't feel it's worth bothering with anymore.