Link Loss Return (LLR)
Both ports on the Radiance SONET single interface line card have been de- signed with LLR for troubleshooting a remote connection. When LLR is enabled*, the port’s transmitter shuts down if its receiver fails to detect a valid receive link. LLR should only be enabled on one end of a cable and is typically enabled on either the unmanaged or remote device. LLR works with in conjunc- tion with Link Loss Carry Forward.
The diagram below shows a typical network configuration with good link status using two SONET line cards for remote connectivity. Note that LLR is enabled as indicated in the diagram.
Management Switch/Hub |
| SONET |
| SONET | Switch/Hub | Remote | |
Station | w/SNMP | Line Card A |
| Line Card B | w/SNMP | Station | |
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|
| LLR2 is ON |
| LLR2 is ON |
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| LLR1 is OFF |
| LLR1 is OFF |
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| Port 2 Port 1 | Remote |
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| |
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| Cable | Port 2 Port 1 |
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| |
LED lit = established link | LED unlit = no link |
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Example: If one of the optical conductors breaks (as shown in the diagram box below), Line Card B, with LLR2 enabled, will return a
Management | Switch/Hub | SONET |
| SONET | Switch/Hub | Remote | |
Station | w/SNMP | Line Card A | Line Card B | w/SNMP | Station | ||
|
| LLR2 is ON |
| LLR2 is ON |
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| |
|
| LLR1 is OFF |
| LLR1 is OFF |
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| |
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| Broken |
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| Port 2 | Conductor | Port 1 |
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| |
Link Loss Carried Forward |
| Link Loss Carried Forward |
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| Link Loss Returned |
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LED lit = established link | LED unlit = no link |
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IMPORTANT: LLR must not be active on both ends of a configuration. If it is, the link can never be established.
*Units are shipped with the LLR function disabled (DOWN).
10 User Guide