Command Reference Guide

3Com Router 3000 Ethernet Family
Command Reference Guide
Chapter 1 System Maintenance and Management
Commands
3Com Corporation
1-8
1.2.4 ip df-check enable
Syntax
ip df-check enable
undo ip df-check enable
View
System view
Parameter
None
Description
Use the ip df-check enable command to enable don’t fragment bit (DF-bit) check for IP
packets.
Use the undo ip df-check enable command to disable DF-bit check for IP packets.
By default, DF-bit check is enabled for IP packets.
With DF-bit check enabled, the router checks the DF bit in the IP header. If an arriving
packet with the DF bit set to 1 is greater than the MTU of the outgoing interface, the
router does not fragment the packet; instead, it drops the packet and sends back an
ICMP message carrying the code of fragmentation needed and DF set.
Before disabling DF-bit check for IP packets, you must ensure that it is disabled on all
the devices along the link.
Example
# Enable DF-bit check for IP packets.
[Router] ip df-check enable
1.2.5 ip option source-routing
Syntax
ip option source-routing
undo ip option source-routing
View
System view
Parameter
None