ECS4660-28F_Management Guide-R03

C HAPTER 49 | IP Interface Commands
IPv6 to IPv4 Tunnels
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tunnel ttl This command configures the TTL (Time to Live) value stored in the IPv4
header of a packet used for tunneling IPv6 traffic. Use the no form to
restore the default value.
SYNTAX
tunnel ttl ttl-value
no tunnel ttl
ttl-value - The TTL value of the IPv4 encapsulating packet.
(Range: 0-255, where zero means that the TTL value is taken from
the Hop Limit set in the IP header of the encapsulated IPv6 packet)
DEFAULT SETTING
0
COMMAND MODE
Interface Configuration (IPv6/v4 Tunnel)
COMMAND USAGE
The command sets the hop limit for the IPv4 encapsulating packet.
However, note that IPv6 over IPv4 tunnels are modeled as a “single-hop.”
That is, the IPv6 hop limit is decremented by only one when an IPv6 packet
traverses the tunnel. The single-hop model serves to hide the existence of
a tunnel. The tunnel is opaque to users of the network, and is not
detectable by network diagnostic tools such as traceroute.
EXAMPLE
Console(config)#interface tunnel 2
Console(config-if)#tunnel ttl 5
Console(config-if)#
show ipv6 tunnel This command displays the status and configuration settings for all IPv6
over IPv4 tunnels.
COMMAND MODE
Privileged Exec
EXAMPLE
Console#show ipv6 tunnel
Tunnel:1
Tunnel Current State : Up
Tunnel Source Address : [VLAN1]192.168.0.3
Tunnel Destination Address : 192.168.0.2
Time to Live : 255
Tunnel Mode (Configured / 6-to-4 / ISATAP) : Configured
Console#