Clocking Issue

[mloraditch]

I have a customer who still has a bunch of Point-to-Point circuits between sites. The carrier does NOT provide clock for the circuits.

I have attached a diagram. All the Lines are T-1s, all the squares are routers, All T-1s are the point to point as above except for the one going to the hexagon, that is an internet T-1 WITH clock from the provider.

R4 and R1 have single T-1 WIC-1DSU-T1 cards. R3 has a VWIC2-2MFT-T1/E1 with the Point to Points and a WIC-1DSU-T1V2 with the internet T-1. The HUB has 2 VWIC2-2MFT-T1/E1s and R2 has a single VWIC2-2MFT-T1/E1.

How should the clocking be set for optimal performance? I can make the HUB Line, R4, R2 and R1 Internal, but then on R3 i have two that need to be internal and one that has to be line, Vice versa same thing, the third t-1 on R3 seems to be my stumbling block.

Thanks much for any assistance!!

[vmiller]

R3 should be clock source for R4s link only

Hub should be clock source for 1 & 2

[Rajesh SB]

Hi ,

I have few questions here before I put my head into this.

1.Could you please tell me if all the T1 point to point circuits mentioned in the diagram are part of data circuit? ( Things gets simpler with clocking if it is data circuits and for clocking  you can refer Scenarion 1: )
2.I need minimum of “show run”, show network-clock”  , “show inv” from all the devices with “hostnames” as mentioned in the diagram.

Scenario 1 (If all the circuits are data):

I believe all the circuits are used for data. in this scenarion we need to take care while providing clocking on VWIC2 cards .
In VWIC2 card if both the ports are used for data ensure you are providing clocking  as "clock source line independent" in the controller .
"independent" means that both ports can be independently clocked.Please find the below observation wrt your toplogy .

HUB (line-independent)-----(line) R1
HUB (Line-independent)-----(line) R2
HUB (line-independent)-----(line) R3

R3  (line-independent)----(line) R4
R3  (line)  -------- (line) any new connection.

Please do let us know if you require more information on this .

Regards
Rajesh SB

[Jhonny Rodriguez]

Data T1 interfaces are showing slip errors under the controllers and it is needed to determine if the clocking configuration is the root cause.

This is related to a known hardware limitation on the VWIC2 cards, as follows:

"On the 2-port T1 Multiflex Trunk VWICs there is only one shared clocking domain between the two T1 controllers. This means that if both T1 controllers are configured to derive clocking from the line then the clock references received must be synchronous or timing slips occur on at least one of the controllers. If the clocking sources are pleisochronous and one controller is configured for clock source line primary and the other for clock source line, then it is likely the second controller will exhibit controlled slips in the output of the show controllers T1 command. This behavior is a hardware limitation of the 2-port T1 Multi-Flex Trunk VWIC product and is by design. However, independent clocking sources can be supported on the 2-port T1/E1 VWIC2 product when both controllers are used for data-only purposes."

See:

http://www.cisco.com/en/US/partner/products/hw/routers/ps274/products_tech_note09186a00800f9d37.shtml

This has been successfully resolved after configuring the clocking source as "line independent" in those links deriving clocking from the line in the VWIC2-2MFT-T1/E1 cards.