Troubleshooting guide

BSR Troubleshooting Guide
4-58
Resolving Problems on the Upstream Path
When the upstream port fault LED is red, the upstream port is not operating and is
not receiving data from the CM subnetwork.
Refer to the procedures in this section to troubleshoot an upstream port problem:
• Bad Upstream Signal-to-noise Ratio Detected
• Upstream Power Level Too Low or High
Bad Upstream Signal-to-noise Ratio Detected
If too much noise is detected on the upstream path a condition called noise
funneling occurs. Noise funneling occurs when the cumulative upstream noise
from anywhere on the HFC network becomes concentrated on the cable headend.
For example, the HFC branch and tree network architecture works in the following
ways:
• Downstream: the trunk feeds the branches. As the signal propagates from the
trunk, the signal weakens.
• Upstream: the branches feed the trunk. As the signal propagates from the
branches, noise and ingress increase.
Follow these steps to troubleshoot ingress noise on the upstream path:
1. To determine the modulation profile number for an upstream port, use the
show cable upstream command in Interface Configuration mode, as shown in
the following example:
RDN(config-if)#show cable <slot>/<interface> upstream <port>
where:
slot is the slot number of the DOCSIS module on the BSR 64000