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222 CHAPTER 16: CONFIGURING LAPB AND X.25
When configuring an Annex G DLCI, the user must explicitly configure it with the
argument DCE or DTE. In addition, the configurations on the routers of a
connection should not be the same. That is, if a router is configured to work as
DTE, the other router must be configured as DCE.
Table 271 Configure the X.25 attributes for an Annex G DLCI
It is necessary to properly understand the differences between the Frame Relay
address map configured in interface view and the X.25 address map configured in
X.25 template view. The former specifies the DLCI from which the packets
destined to an IP address can be sent, whereas the latter specifies the X.25 address
to which the packets must originate X.25 calls in order to reach the destination IP
address. IP packets can be properly sent and received on the Annex G DLCI only if
the two address maps are configured.
The LAPB/X.25 attributes configured in an X.25 template and those configured on
an X.25 interface are similar. To ensure that an X.25 call can be set up, the
configurations on the routers of a connection should keep in consistency.
1 Configure the X.25 Attributes for a DLCI
Frame Relay is mainly applied to data transmission. However, it does not provide
acknowledgement mechanism or error correction function. In other words,
transmission over Frame Relay networks is unreliable. To ensure reliable
transmission of signals for call set up and termination in dynamic calling mode,
these signals are transmitted over an X.25 VC (Virtual Circuit). Thereby, reliable
transmission can be ensured through the X.25 message acknowledgement
mechanism. A DLCI needs to be configured with X.25 attributes only when VoFR
(Voice over Frame Relay) adopts dynamic calling mode.
The x.25 template command is performed in system view. Creating an X.25
template will enter x.25 template mode at the same time. Perform the commands
x25 and lapb in x.25 template mode, and x25-template in interface DLCI mode.
Table 272 Configure the X.25 attributes for an DLCI
Operation Command
Create an X.25 template x25 template { name }
Configure the local X.25 address in the X.25
template
x25 x121-address x.121 address
Map the destination X.25 address to the
destination IP address in the X.25 template
x25 map ip { A.B.C.D } {
x121-address x.121 address }
Configure other LAPB/X.25 parameters in the
X.25 template
For details, refer to the
LAPB/X.25 configuration commands.
Associate the parameters configured in the
X.25 template to an Annex G DLCI
x25-template { name }
Operation Command
Create an X.25 template x25 template name
Delete the X.25 template no x25 template name
Configure the X.25 attributes x25
Restore the X.25 attributes to default settings no x25
Configure the LAPB attributes lapb
Restore the LAPB attributes to default
settings
no lapb
Associate the X.25 template with a DLCI x25-template name
Remove the association between the X.25
template and the DLCI
no x25-template