Cisco Cisco IOS Software Releases 12.2 MC

To collect data for reporting back card and router issues, issue the following commands:

show tech-support—Displays general information about the router when it reports a problem.

show logging—Displays information in the syslog history table.

When PPP multiplexing is disabled on the inbound direction of a MWR 1941-DC multilink, there are 
many more packets to reorder. Therefore, we recommend that you modify the MLP reorder buffer using 
the ppp multilink slippage interface configuration commands to avoid discarded fragments due to 
buffer overflow.

Slippage is the amount by which data arriving on one link in a multilink bundle might lag behind data 
transmitted over another link in that bundle. The amount of slippage might be expressed as a direct byte 
count, but it is also commonly expressed as a measure of time, in terms of the differential delay between 
the links.

A small amount of slippage between links is normal. Whenever slippage occurs, the multilink input 
process must buffer fragment data arriving on the faster channels until it receives all expected fragments 
on the remaining links, so that it can sort the fragments back into proper order, reassemble datagrams as 
necessary, and then deliver the datagrams in proper order to the higher network layers (multilink 
fragments include sequence numbers so that the multilink receiver can readily detect when packets are 
arriving out of order). The receiver must be capable of buffering enough data to compensate for normal 
slippage between the links, otherwise it will be incapable of completely sequencing and reassembling 
datagrams, and some data will be lost.

With Cisco IOS Release 12.2(15)MC1 and later, the MLP reorder buffer can be adjusted for cases where 
the slippage is larger than the defaults readily accommodate. The buffer size is set by defining a one or 
more constraints, each of which indirectly implies some byte limit. The limit used is the maximum of 
the value derived from the constraints.

To define the constraints that set the MLP reorder buffer size, issue the following commands while in 
interface configuration mode:

Router(config-if)# ppp multilink slippage mru value

Specifies that the buffer limit is x bytes where the 
byte count is expressed as a multiple of the 
maximum receive unit (MRU) negotiated for the 
bundle (the buffer limit is derived as the number of 
times defined for the value times the size of the 
largest packet received). Valid values are 2 through 
32. The default is 8.

The MRU is dynamically negotiated with 
the peer when the connection is 
established, therefore, the byte count also 

Router(config-if)# ppp multilink slippage msec value

Specifies the buffer limit, in milliseconds worth of 
data. Valid range is 1 to 16000.

The actual amount of data buffered 
depends upon the bandwidth of the links.