Cisco Cisco Packet Data Interworking Function (PDIF)
WSG Service Configuration Mode Commands
pre_fragment mtu ▀
Command Line Interface Reference, StarOS Release 18 ▄
9103
pre_fragment mtu
Specifies the Maximum Transmission Unit (MTU) size which when exceeded initiates pre-tunnel (before encryption)
fragmentation of IPSec Encapsulated Security Payload (ESP) packets within this WSG service (VPC only).
fragmentation of IPSec Encapsulated Security Payload (ESP) packets within this WSG service (VPC only).
Product
SecGW (WSG)
Privilege
Security Administrator
Mode
Exec > Global Configuration > Context Configuration > WSG-Service Configuration
configure > context context_name > wsg-service
service_name
Entering the above command sequence results in the following prompt:
[context_name]host_name(config-wsg-service)#
Syntax
pre_fragment mtu size
no pre_fragment size
default pre_fragment size
no
Disables this function.
default
Sets the MTU size to the default value of 1400 bytes.
mtu
size
Specifies the MTU size in bytes as an integer from 576 through 2048. Default = 1400
Usage
Specify the MTU size which when exceeded initiates pre-tunnel fragmentation of IPSec ESP packets within
this WSG service.
Pre-Tunnel-Fragmentation improves packet processing performance as compared to post-tunnel-
fragmentation.
If a clear IPv4 packet is longer than the predefined MTU size, it will be fragmented before the packet is
encrypted and transmitted to internet.
If a clear IPv6 packet is longer than the predefined MTU size, it is dropped and an ICMP packet with the
maximum length is sent back to the source. The source will then fragment the IPv6 packet and retransmit.
this WSG service.
Pre-Tunnel-Fragmentation improves packet processing performance as compared to post-tunnel-
fragmentation.
If a clear IPv4 packet is longer than the predefined MTU size, it will be fragmented before the packet is
encrypted and transmitted to internet.
If a clear IPv6 packet is longer than the predefined MTU size, it is dropped and an ICMP packet with the
maximum length is sent back to the source. The source will then fragment the IPv6 packet and retransmit.
Example
The following command sets MTU size to 2048 bytes.
pre_fragment mtu 2048