I have a Cisco 3640. It has been running with a single WIC-2T that is connected to an Adtran IQ710 running at the hub of our frame relay WAN. The frame relay port is a full T1 attached to Serial0/1.
We want to replace the frame relay network with MPLS, and this MPLS cicuit is using three full T1's. The frame relay T1 will eventually go away, but during the transition we need to keep the old frame T1 up as well as the three new MPLS T1's.
The MPLS T1's are also using Adtran IQ710 CSU/DSU's.
We have purchased a second WIC-2T and installed it in the 3640 router. The MPLS serial ports are Serial0/0, Serial0/2 and Serial0/3. We are using multilink PPP to bind them together.
With the original (old) WIC-2T in the [s0/0,s0/1] slot the frame relay (s0/1) port comes up and the s0/0 MPLS T1 comes up. But s0/2 and s0/3 do not. In other words when we do a show ppp multilink; serial0/2 and serial0/3 both show inactive.
With the original (old) WIC-2T in the [s0/2,s0/3] slot the frame relay port (s0/1) also comes up. But now the MPLS situation is reversed. Serial0/2 and serial0/3 both come up but now when we do a show ppp multilink; serial0/0 shows inactive.
Suspecting that we may have a bad new WIC-2T card, we obtained another. With the two new WIC-2T cards installed, only the frame relay T1 on serial0/1 would come up. All three of the MPLS T1 serial ports showed inactive.
Thinking that there may be some kind of bandwidth limit that was limiting us to three full T1's, we unplugged the frame T1 and put the old card on the [s0/2,s0/3] slot. Only s0/2 & s0/3 came up, s0/0 was still inactive.
The three bonded MPLS T1's are using HDLC to connect to the MPLS network per telco's recommendation. We were told frame relay encapsulation was also an option, but with frame relay encapsulation, one T1 going down would bring the whole link down. The Adtran IQ710's are CSU's with features geared for frame relay monitoring and traffic shaping. But I cannot find anything that says they will not work as simple CSU's. And in fact all three of the Adtran CSU's have worked on the MPLS circuit (just not all at the same time).
Right now I have put the old card in the [s0/2,s0/3] slot and have those two T1s active on the ppp multilink. I am looking for what I need to do to get the third and final (s0/0) T1 on the multilink to come up.