Label Distribution Protocol 
492
MPLS Guide
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Transport Address interface — the interface IP address is used to set up the LDP 
session between neighbors. If multiple interfaces exist between 
two neighbors, the interface mode cannot be used since only one 
LDP session is actually set up between the two neighbors.
system — the system IP address is used to set up the LDP 
session between neighbors
Label-Distribution The label distribution method
Label-Retention liberal — all advertised label mappings are retained whether they 
are from a valid next hop or not. When the label distribution value 
is downstream unsolicited, a router may receive label bindings for 
the same destination for all its neighbors. Labels for the non-next-
hops for the FECs are retained in the software but not used. 
When a network topology change occurs where a non-next-hop 
becomes a true next hop, the label received earlier is then used.
conservative — advertised label mappings are retained only if 
they will be used to forward packets; for example if the label came 
from a valid next hop. Label bindings received from non-next-
hops for each FEC are discarded.
Control Mode ordered — label bindings are not distributed in response to a label 
request until a label binding has been received from the next hop 
for the destination
independent — label bindings are distributed immediately in 
response to a label request even if a label binding has not yet 
been received from the next hop for the destination
Route Preference The route preference assigned to LDP routes. When multiple 
routes are available to a destination, the route with the lowest 
preference will be used. This value is only applicable to LDP 
interfaces and not for targeted sessions.
IPv4 Targeted Session Parameters
IPv6 Targeted Session Parameters
Keepalive Timeout The factor used to derive the keepalive interval
Keepalive Factor The time interval, in seconds, that LDP waits before tearing down 
the session
Hold Time The time left before a neighbor is declared to be down
Table 46 LDP Parameters Field Descriptions (Continued)
Label Description