552 Chapter 8: WAN Protocols and Design
Determining when and how to use subinterfaces for Frame Relay configuration is the most
difficult part of the configuration. Subinterfaces are never required; subinterfaces can be used
in any Frame Relay configuration, and most sites tend to use them. Some general guidelines
when using subinterfaces include the following:
·
When the network is partially meshed, using point-to-point subinterfaces overcomes split
horizon issues by treating each subinterface as a separate interface.
·
When the network is partially meshed, using a multipoint subinterface will work.
·
When the network is truly fully meshed, a multipoint subinterface can be used to reduce
the number of network-layer groups (for example, IP subnets) that are used.
frame-relay map protocol
protocol-address dlci [payload-
compress {packet-by-packet |
frf9 stac}] [broadcast] [ietf |
cisco]
Interface
Statically defines a mapping
between a network layer address
and a DLCI.
keepalive sec
Interface
Defines whether and how often
LMI status enquiry messages
are sent and expected.
interface serial num.sub [point-
to-point | multipoint]
Global
Creates a subinterface, or
references a previously created
subinterface.
frame-relay interface-dlci dlci
[ietf | cisco]
Interface
Defines a DLCI used for a VC to
another DTE.
frame-relay payload-compress
{packet-by-packet | frf9 stac}
Interface subcommand
Defines payload compression on
point-to-point subinterfaces.
Table 8-23
Frame Relay Related EXEC Commands
Command
Function
show interface
Shows physical interface status.
show frame-relay {pvc | map |
lmi }
Shows PVC status, mapping (dynamic and static), and LMI status.
debug frame-relay {lmi |
events}
Lists messages describing LMI flows (LMI option). The events
option lists inverse ARP information. Other options include lapf,
informationelements, ppp, and packet.
Table 8-22
Frame Relay Configuration Commands (Continued)
Command
Configuration Mode
Purpose
ch08.fm Page 552 Monday, March 20, 2000 5:17 PM