R2511-HP MSR Router Series Layer 2 - WAN Command Reference(V5)

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LAPB and X.25 configuration commands
The MSR900 and MSR93X routers do not support LAPB or X.25.
LAPB configuration commands
lapb max-frame
Use lapb max-frame to configure the LAPB N1 parameter.
Use undo lapb max-frame to restore the default.
Syntax
lapb max-frame n1-value
undo lapb max-frame
Default
The value of N1 is calculated according to the MTU, upper layer protocol, and modulo.
Views
Interface view
Default command level
2: System level
Parameters
n1-value: N1 value of the LAPB parameter in bits, in the range 1096 to 12104. It is the maximum number
of I frames expected from the DTE or DCE, 8 times the value of MTU plus the protocol header.
Usage guidelines
Table 67 Difference between N1 and MTU versus upper layer protocol and modulo
Upper layer protocol Modulo
Difference between N1 and
MTU (in b
y
tes)
IP/IPX 8 4
IP/IPX 128 5
Multiprotocol 8 6
Multiprotocol 128 7
X.25 8 7
X.25 128 8
The default value of N1 varies with MTU and modulo.
For example, on system initialization, the upper layer protocol is IP, modulo 8 and MTU 1500, so the
default value of N1 is (1500+4)*8 = 12032. If the modulo is set to 128, then the default value of N1 is