Lucent Technologies 6000 User Manual

MAX 6000/3000 Network Configuration Guide

 11-5

is unreachable without fragmentation. This standard, expected behavior improves end-to-end 
performance by enabling the connection end-points to perform any required fragmentation and 
reassembly. 

However, some outdated client software does not handle this process correctly and continues 
to send packets that are larger than the specified GRE MTU. To enable the MAX to 
interoperate with these clients, you can configure the MAX to ignore the DF bit and perform 
the fragmentation that normally should be performed by the client software. This function in 
the MAX is sometimes referred to as prefragmentation. To enable it, set the Force 
Fragmentation parameter to Yes. The MAX unit then prefragments the packets, before adding 
the GRE and IP headers. 

Setting the Force fragmentation parameter to Yes causes the MAX to bypass the 

standard MTU discovery mechanism and fragment larger packets before encapsulating them in 
GRE. Because this changes expected behavior, it is not recommended except for ATMP 
interoperation with outdated client software that does not handle fragmentation properly.

The Home Agent can communicate with the home network through a direct connection, 
through another router, or across a nailed connection. When the Home Agent relies on packet 
routing to reach the home network, it operates in router mode. When it has a nailed connection 
to the home network, it is in gateway mode.

Following are the parameters (shown with sample settings) related to Foreign Agent 
configuration:

Ethernet

Mod Config

ATMP options...

ATMP Mode=Foreign

Type=N/A

Password=N/A

SAP Reply=N/A

UDP Port=5150

GRE MTU=1472

Force fragmentation=No

Idle limit=N/A

ATMP SNMP Traps=No

Following are the parameters (shown with sample settings) for the IP routing connection to the 
Home Agent:

Ethernet

Mod Config

Ether options...

IP Adrs=10.65.212.226/24

Ethernet

Connections