VLAN Keywords ============= .. role:: example-rule-action .. role:: example-rule-header .. role:: example-rule-options .. role:: example-rule-emphasis vlan.id ------- Suricata has a ``vlan.id`` keyword that can be used in signatures to identify and filter network packets based on Virtual Local Area Network IDs. By default, it matches all layers if a packet contains multiple VLAN layers. However, if a specific layer is defined, it will only match that layer. Syntax:: vlan.id: [op]id[,layer]; The id can be matched exactly, or compared using the ``op`` setting:: vlan.id:300 # exactly 300 vlan.id:<300,0 # smaller than 300 at layer 0 vlan.id:>=200,1 # greater or equal than 200 at layer 1 vlan.id uses :ref:`unsigned 16-bit integer `. The valid range for VLAN id values is ``0 - 4095``. This keyword also supports ``all`` and ``any`` as arguments for ``layer``. ``all`` matches only if all VLAN layers match and ``any`` matches with any layer. .. table:: **Layer values for vlan.id keyword** =============== ================================================ Value Description =============== ================================================ [default] Match with any layer 0 - 2 Match specific layer ``-3`` - ``-1`` Match specific layer with back to front indexing all Match only if all layers match any Match with any layer =============== ================================================ This small illustration shows how indexing works for vlan.id:: [ethernet] [vlan 666 (index 0 and -2)] [vlan 123 (index 1 and -1)] [ipv4] [udp] Examples ^^^^^^^^ Example of a signature that would alert if any of the VLAN IDs is equal to 300: .. container:: example-rule alert ip any any -> any any (msg:"Vlan ID is equal to 300"; :example-rule-emphasis:`vlan.id:300;` sid:1;) Example of a signature that would alert if the VLAN ID at layer 1 is equal to 300: .. container:: example-rule alert ip any any -> any any (msg:"Vlan ID is equal to 300 at layer 1"; :example-rule-emphasis:`vlan.id:300,1;` sid:1;) Example of a signature that would alert if the VLAN ID at the last layer is equal to 400: .. container:: example-rule alert ip any any -> any any (msg:"Vlan ID is equal to 400 at the last layer"; :example-rule-emphasis:`vlan.id:400,-1;` sid:1;) Example of a signature that would alert only if all the VLAN IDs are greater than 100: .. container:: example-rule alert ip any any -> any any (msg:"All Vlan IDs are greater than 100"; :example-rule-emphasis:`vlan.id:>100,all;` sid:1;) It is also possible to use the vlan.id content as a fast_pattern by using the ``prefilter`` keyword, as shown in the following example. .. container:: example-rule alert ip any any -> any any (msg:"Vlan ID is equal to 200 at layer 1"; :example-rule-emphasis:`vlan.id:200,1; prefilter;` sid:1;) vlan.layers ----------- Matches based on the number of layers. Syntax:: vlan.layers: [op]number; It can be matched exactly, or compared using the ``op`` setting:: vlan.layers:3 # exactly 3 vlan layers vlan.layers:<3 # less than 3 vlan layers vlan.layers:>=2 # more or equal to 2 vlan layers vlan.layers uses :ref:`unsigned 8-bit integer `. The minimum and maximum values that vlan.layers can be are ``0`` and ``3``. Examples ^^^^^^^^ Example of a signature that would alert if a packet has 0 VLAN layers: .. container:: example-rule alert ip any any -> any any (msg:"Packet has 0 vlan layers"; :example-rule-emphasis:`vlan.layers:0;` sid:1;) Example of a signature that would alert if a packet has more than 1 VLAN layers: .. container:: example-rule alert ip any any -> any any (msg:"Packet has more than 1 vlan layer"; :example-rule-emphasis:`vlan.layers:>1;` sid:1;) It is also possible to use the vlan.layers content as a fast_pattern by using the ``prefilter`` keyword, as shown in the following example. .. container:: example-rule alert ip any any -> any any (msg:"Packet has 2 vlan layers"; :example-rule-emphasis:`vlan.layers:2; prefilter;` sid:1;)