Lucent Technologies 6000 - Manual (Page 439)

Setting Up Virtual Private Networks
Configuring ATMP tunnels
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However, some outdated client software does not handle this process correctly and continues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.
Note: 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interoperation with outdated client software that does not handle fragmentation properly.
Router and gateway mode
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.
Configuring the Foreign Agent
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
90-101 Connection profile 1