Choose your PSTN simulator carefully

When trying to finalise my PSTN configuration for the required E1 and T1 lines to HQ, BR1 and BR2 I stumbled into a set of limitations with the 2801 router that caused me to stop and redo my topology.

Originally I had the following setup:



The 2801 was configured as follows

Slot0-VWIC2-2MFT-T1/E1 (T1 crossover to HQ and BR1 )
Slot 1-
VWIC2-2MFT-T1/E1 (E1 crossover to BR2)
Slot 2-
Slot 3-

Frame relay switching was enabled with no issues for all three sites but when I tried to enable the pri timeslots on the controller in slot 0, I kept getting an error saying insufficient resources. At first I wasn’t sure what was wrong so moved on to the controller in slot 1 and configured the E1 pri timeslots with no problems. A quick google lookup pointed out that the 2801 routers can only use a T1 CAS voice card in slot 0 and nothing else. As the lab scenarios for HQ and BR1 required PRI and I was out of slots to relocate to, I now have to use the 2801 as a site router and replace it with a 2811 router instead.


One thought on “Choose your PSTN simulator carefully

  1. Just a quick update as I was able to return my 2801 as my backbone router by removing my two WIC-2T cards and replacing them with VWIC2-2MFT-T1/E1 cards. This move has standardized the lab to all RJ-48 connectors for both PSTN and FRAME relay. My new layout is as follows:
    Slot 0-VWIC2-2MFT-T1/E1 (port1:T1 crossover to HQ, port2:Frame relay to HQ)
    Slot 1-VWIC2-2MFT-T1/E1 (port1:T1 crossover to BR1, port2:Frame relay to BR1)
    Slot 2-VWIC2-2MFT-T1/E1 (port1:E1 crossover to BR2, port2:Frame relay to BR2)
    Slot 3-4FXS (additional lines for PSTN as I my 7962 phone died and I am currently using a 7941 which only gives me two lines)


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