---
name: "sl"
section: "4"
platform: "linux"
package: "freebsd-manpages"
version: "6.0-5"
release: "Debian 4.0 (Etch)"
platforms: ["linux"]
url: "https://new.carta.tech/sl/4"
---

# sl(4)

slip network interface

## NAME

**sl** – slip network interface

## SYNOPSIS

**device sl** \[*count*\]

## DESCRIPTION

The **sl** interface allows serial lines to be used as network interfaces using the *slip* protocol. The **sl** interface can use Van Jacobson TCP header compression and ICMP filtering. This is arranged by using the various link-level flags to the [ifconfig(8)](/ifconfig/8.md) command:

- *link0*

  Enable VJ header compression.

- *link1*

  Suppress ICMP traffic.

- *link2*

  Enable VJ header compression autodetection. This will turn on the *link0* flag as soon as the first VJ-compressed packet has been seen by the driver.

## DIAGNOSTICS

- sl%d: af%d not supported.

  The interface was handed a message with addresses formatted in an unsuitable address family; the packet was dropped.

## SEE ALSO

[inet(4)](/inet/4.md), [intro(4)](/intro/4.md), [slattach(8)](/slattach/8.md), [sliplogin(8)](/sliplogin/8.md), slstat(8)