---
name: "ipsec_tncfg"
section: "5"
platform: "linux"
package: "openswan"
version: "1:2.6.37-3+deb7u1"
release: "Debian 7 (Wheezy)"
platforms: ["linux"]
url: "https://new.carta.tech/ipsec_tncfg/5"
---

# ipsec\_tncfg(5)

lists IPSEC virtual interfaces attached to real interfaces

## NAME

ipsec\_tncfg - lists IPSEC virtual interfaces attached to real interfaces

## SYNOPSIS

**ipsec** *tncfg*\
 *cat/proc/net/ipsec\_tncfg*

## OBSOLETE

Note that tncfg is only supported on the classic KLIPS stack. It is not supported on any other stack and will be completely removed in future versions. A replacement command still needs to be designed

## DESCRIPTION

/proc/net/ipsec\_tncfg is a read-only file which lists which IPSEC virtual interfaces are attached to which real interfaces, through which packets will be forwarded once processed by IPSEC.

Each line lists one ipsec I/F. A table entry consists of:

\+

an ipsec virtual I/F name

\+

a visual and machine parsable separator ´-\>´, separating the virtual I/F and the physical I/F,

\+

a physical I/F name, to which the ipsec virtual I/F is attached or NULL if it is not attached,

\+

the keyword **mtu=**,

\+

the MTU of the ipsec virtual I/F,

\+

the automatically adjusted effective MTU for PMTU discovery, in brackets,

\+

a visual and machine parsable separator ´-\>´, separating the virtual I/F MTU and the physical I/F MTU,

\+

the MTU of the attached physical I/F.

## EXAMPLES

**ipsec2 -\> eth3 mtu=16260(1443) -\> 1500**

shows that virtual device **ipsec2** with an MTU of 16260 is connected to physical device **eth3** with an MTU of 1500 and that the effective MTU as a result of PMTU discovery has been automatically set to 1443.

**ipsec0 -\> wvlan0 mtu=1400(16260) -\> 1500**

shows that virtual device **ipsec0** with an MTU of 1400 is connected to physical device **wvlan0** with an MTU of 1500 and no PMTU packets have gotten far enough to bump down the effective MTU from its default of 16260.

**ipsec3 -\> NULL mtu=0(0) -\> 0**

shows that virtual device **ipsec3** is not connected to any physical device.

## FILES

/proc/net/ipsec\_tncfg, /usr/local/bin/ipsec

## SEE ALSO

[ipsec(8)](/ipsec/8.md), [ipsec\_manual(8)](/ipsec_manual/8.md), [ipsec\_eroute(5)](/ipsec_eroute/5.md), [ipsec\_spi(5)](/ipsec_spi/5.md), [ipsec\_spigrp(5)](/ipsec_spigrp/5.md), [ipsec\_klipsdebug(5)](/ipsec_klipsdebug/5.md), [ipsec\_tncfg(8)](/ipsec_tncfg/8.md), [ipsec\_version(5)](/ipsec_version/5.md), [ipsec\_pf\_key(5)](/ipsec_pf_key/5.md)

## HISTORY

Written for the Linux FreeS/WAN project \<**http://www.freeswan.org/**\> by Richard Guy Briggs.