Tracy,
Your configuration works because you are using two separate VWIC cards. The rule for VWIC cards is that the entire card, and all its ports, must either participate in network clock or NOT participate. In your case you have WIC 1 which is participating and WIC 0 which is not. For cards that do participate only one port can be the 'reference' clock for the router at any one time. Thus the network-clock-select command sets up a hierarchy of ports to take over the reference clock role if the primary port goes down.
PRI-ISDN circuits require the network-clock-participate command so you had to select them as the clock source for the router. Data circuits, however, don't require it so they can be free-floating and/or run independently of the backplane/network-clock if you don't tell the card they are on to participate in the backplane/network clock source
The larger question you need to ask is why AT&T and Century Link (once Qwest) aren't using the same TDM clock source? If a one carrier 's T1/E1 clock is not synced with another carrier's T1/E1 clock source then it is time to find out why. PRI-ISDN circuits from tier 1 carriers are nominally synced from a stratum 1 source thus, IMHO, PRI-ISDN circuits usually are the best sources for TDM clock on a router.
Thus you might want to ask if the clock skew coming from one of your NIU's, is it the distance to your CO, a bad card somewhere? Might be worth the trouble to ask for a lineman to come out and verify your circuits are good.
Edit: You might simply check the quality, condition, and length of your cables.
-Steven
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Message was edited by: Steven Griffin
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