Add VPP IPFIX configuration

Author: sever-sever

docs/vpp/configuration/index.rst

@@ -26,6 +26,7 @@ Features that can be enabled on VPP Dataplane:
    :includehidden:
 
    acl
+   ipfix
    ipsec
    nat/index
    sflow

docs/vpp/configuration/ipfix.rst

@@ -0,0 +1,50 @@
+VPP IPFIX Configuration
+=======================
+
+VPP IPFIX in VyOS allows monitoring and exporting network traffic flows
+for analytics, security, and accounting. IPFIX works with the VPP
+(Vector Packet Processing) backend to provide high-performance flow tracking.
+
+Overview
+--------
+
+VyOS integrates VPP for high-performance packet processing. IPFIX
+configuration controls how flows are monitored, exported, and which
+interfaces are included.  
+
+Key IPFIX Concepts
+------------------
+
+- **Active timeout**: Maximum time a flow is kept active before export.
+- **Inactive timeout**: Maximum time an idle flow is kept before export.
+- **Collector**: The remote host and port to which flow records are sent.
+- **Flow layers**: Determines which layer information is included (`l2`, `l3`, `l4`).
+- **Interfaces**: Physical or virtual interfaces to monitor.
+- **Direction**: Which traffic to monitor (`rx`, `tx`, `both`).
+- **Flow variant**: Optional filter for IPv4 or IPv6 flows.
+
+Configuration Options
+---------------------
+
+- **active-timeout**: Duration (in seconds) after which active flows are exported.
+- **inactive-timeout**: Duration (in seconds) after which idle flows are exported.
+- **collector `<ip>` port `<port>`**: IP and UDP port of the IPFIX collector.
+- **collector `<ip>` source-address `<ip>`**: Source address for flow export.
+- **flowprobe-record `<l2|l3|l4>`**: Layers to include in flow records.
+- **interface `<interface>` [direction `<rx|tx|both>`] [flow-variant `<ipv4|ipv6>`]**: Interfaces to monitor, direction of traffic, and optional flow variant filter.
+
+Example Configuration
+---------------------
+
+.. code-block:: none
+
+    set vpp ipfix active-timeout '15'
+    set vpp ipfix inactive-timeout '120'
+    set vpp ipfix collector 192.0.2.2 port '4739'
+    set vpp ipfix collector 192.0.2.2 source-address '192.0.2.1'
+    set vpp ipfix flowprobe-record 'l2'
+    set vpp ipfix flowprobe-record 'l3'
+    set vpp ipfix flowprobe-record 'l4'
+    set vpp ipfix interface eth0
+    set vpp ipfix interface eth1 direction 'both' flow-variant 'ipv4'
+