H3C SOHO IE4300, Command Reference Manual

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Syntax
ttl-security [ hops hop-count ]
undo ttl-security
Default
OSPF GTSM is disabled for an OSPF area.
Views
OSPF area view
Predefined user roles
network-admin
Parameters
hops hop-count
: Specifies the hop limit for checking OSPF packets, in the range of 1 to 254. The
default hop limit is 1 for packets from common neighbors, and is 255 for packets from virtual link
neighbors.
Usage guidelines
After you enable GTSM in area view, GTSM checks OSPF packets from common neighbors and
virtual link neighbors.
GTSM protects the device by comparing the TTL value in the IP header of incoming OSPF packets
against a valid TTL range. If the TTL value is within the valid TTL range, the packet is accepted. If not,
the packet is discarded.
The valid TTL range is from 255 – the configured hop count + 1 to 255.
When GTSM is configured, the OSPF packets sent by the device have a TTL of 255. To use GTSM,
you must configure GTSM on both the local and peer devices. You can specify different
hop-count
values for them.
The GTSM configuration in OSPF area view applies to all OSPF interfaces in the area. The GTSM
configuration in interface view takes precedence over the configuration in OSPF area view.
As a best practice, set the hop limit if a virtual link exists in an area. You can enable GTSM for the
interfaces on the virtual link. If you do not know the interfaces on the virtual link, enable GTSM in
area view to prevent packet loss.
Examples
# Enable OSPF GTSM for OSPF area 1.
<Sysname> system-view
[Sysname] ospf 100
[Sysname-ospf-100] area 1
[Sysname-ospf-100-area-0.0.0.1] ttl-security
Related commands
ospf ttl-security
vlink-peer (OSPF area view)
Use
vlink-peer
to configure a virtual link.
Use undo vlink-peer to remove a virtual link.