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Workaround and fixes for the current Core Dump Handling vulnerability affected kernels

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April, 26th. 2006:

You are here: manpages


Section: Linux (8)
Updated: 20 Dec 2011
Index Return to Main Contents


ip-tunnel - tunnel configuration  


ip tunnel help

ip [ OPTIONS ] tunnel { add | change | del | show | prl | 6rd } [ NAME ]
[ mode MODE ] [ remote ADDR ] [ local ADDR ]
[ [i|o]seq ] [ [i|o]key KEY ] [ [i|o]csum ] ]
[ encaplimit ELIM ] [ ttl|hoplimit TTL ]
[ tos TOS ] [ flowlabel FLOWLABEL ]
[ prl-default ADDR ] [ prl-nodefault ADDR ] [ prl-delete ADDR ]
[ 6rd-prefix ADDR ] [ 6rd-relay_prefix ADDR ] [ 6rd-reset ]
[ [no]pmtudisc ] [ [no]ignore-df ] [ dev PHYS_DEV ]

MODE := { ipip | gre | sit | isatap | vti | ip6ip6 | ipip6 | ip6gre | vti6 | }

ADDR := { IP_ADDRESS | any }

TOS := { STRING | 00..ff | inherit | inherit/STRING | inherit/00..ff }

ELIM := { none | 0..255 }

TTL := { 1..255 | inherit }




tunnel objects are tunnels, encapsulating packets in IP packets and then sending them over the IP infrastructure. The encapsulating (or outer) address family is specified by the -f option. The default is IPv4.

ip tunnel add
add a new tunnel
ip tunnel change
change an existing tunnel
ip tunnel delete
destroy a tunnel
name NAME (default)
select the tunnel device name.

mode MODE
set the tunnel mode. Available modes depend on the encapsulating address family.
Modes for IPv4 encapsulation available: ipip, sit, isatap, vti, and gre.
Modes for IPv6 encapsulation available: ip6ip6, ipip6, ip6gre, vti6, and any.

remote ADDRESS
set the remote endpoint of the tunnel.

set the fixed local address for tunneled packets. It must be an address on another interface of this host.

ttl N
hoplimit N
set a fixed TTL (IPv4) or hoplimit (IPv6) N on tunneled packets. N is a number in the range 1--255. 0 is a special value meaning that packets inherit the TTL value. The default value for IPv4 tunnels is: inherit. The default value for IPv6 tunnels is: 64.

tos T
dsfield T
tclass T
set the type of service (IPv4) or traffic class (IPv6) field on tunneled packets, which can be specified as either a two-digit hex value (e.g. c0) or a predefined string (e.g. internet). The value inherit causes the field to be copied from the original IP header. The values inherit/STRING or inherit/00..ff will set the field to STRING or 00..ff when tunneling non-IP packets. The default value is 00.

dev NAME
bind the tunnel to the device NAME so that tunneled packets will only be routed via this device and will not be able to escape to another device when the route to endpoint changes.

disable Path MTU Discovery on this tunnel. It is enabled by default. Note that a fixed ttl is incompatible with this option: tunneling with a fixed ttl always makes pmtu discovery.

enable IPv4 DF suppression on this tunnel. Normally datagrams that exceed the MTU will be fragmented; the presence of the DF flag inhibits this, resulting instead in an ICMP Unreachable (Fragmentation Required) message. Enabling this attribute casues the DF flag to be ignored.

key K
ikey K
okey K
( only GRE tunnels ) use keyed GRE with key K. K is either a number or an IP address-like dotted quad. The key parameter sets the key to use in both directions. The ikey and okey parameters set different keys for input and output.

csum, icsum, ocsum
( only GRE tunnels ) generate/require checksums for tunneled packets. The ocsum flag calculates checksums for outgoing packets. The icsum flag requires that all input packets have the correct checksum. The csum flag is equivalent to the combination icsum ocsum.

seq, iseq, oseq
( only GRE tunnels ) serialize packets. The oseq flag enables sequencing of outgoing packets. The iseq flag requires that all input packets are serialized. The seq flag is equivalent to the combination iseq oseq. It doesn't work. Don't use it.

encaplim ELIM
( only IPv6 tunnels ) set a fixed encapsulation limit. Default is 4.

flowlabel FLOWLABEL
( only IPv6 tunnels ) set a fixed flowlabel.

ip tunnel prl
potential router list (ISATAP only)
dev NAME
mandatory device name.

prl-default ADDR
prl-nodefault ADDR
prl-delete ADDR
Add or delete ADDR as a potential router or default router.

ip tunnel show
list tunnels This command has no arguments.






Original Manpage by Michail Litvak <>




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