---
# System prepended metadata

title: '網路模擬與分析(5/17): P4'
tags: [P4, Mininet]

---

# 網路模擬與分析(5/17): P4
###### tags: `Mininet`、`P4`

---

**--------------目前為純 code 及 result，詳解部分之後更新--------------**

---

![](https://i.imgur.com/mmVshQ8.png)

## MAC Layer Forwarding


![](https://i.imgur.com/eZb5a2L.png)


`p4app.json`: 

```
 {

 	"program": "basic.p4",

 	"switch": "simple_switch",

 	"compiler": "p4c",

 	"options": "--target bmv2 --arch v1model --std p4-16",

 	"switch_cli": "simple_switch_CLI",

 	"cli": true,

 	"pcap_dump": true,

 	"enable_log": true,

 	"topo_module": {

 		"file_path": "",

 		"module_name": "p4utils.mininetlib.apptopo",

 		"object_name": "AppTopoStrategies"

 	},

 	"controller_module": null,

 	"topodb_module": {

 		"file_path": "",

 		"module_name": "p4utils.utils.topology",

 		"object_name": "Topology"

 	},

 	"mininet_module": {

 		"file_path": "",

 		"module_name": "p4utils.mininetlib.p4net",

 		"object_name": "P4Mininet"

 	},

 	"topology": {

 		"assignment_strategy": "l2",

 		"links": [["h1", "s1"], ["h2", "s1"]],

 		"hosts": {

 			"h1": {

 			},

 			"h2": {

 			}

 		},

 		"switches": {

 			"s1": {

 				"cli_input": "cmd.txt",

 				"program": "basic.p4"

 			}

 		}

 	}

 }
```

`basic.p4`:

```
 /* -*- P4_16 -*- */
 #include <core.p4>
 #include <v1model.p4>

 /*************************************************************************
 *********************** H E A D E R S  ***********************************
 *************************************************************************/

 header ethernet_t {
 		bit<48> dstAddr;
 		bit<48> srcAddr;
 		bit<16>   etherType;
 }

 
 struct metadata {
 		/* empty */
 }

 

 struct headers {
 	ethernet_t   ethernet;
 }

 

 /*************************************************************************
 *********************** P A R S E R  ***********************************
 *************************************************************************/

 parser MyParser(packet_in packet,
 								out headers hdr,
 								inout metadata meta,
 								inout standard_metadata_t standard_metadata) {

 		state start {
 				transition parse_ethernet;
 		}

 		state parse_ethernet {
 				packet.extract(hdr.ethernet);
 				transition accept;
 		}	
 }

 

 /*************************************************************************

 ************   C H E C K S U M    V E R I F I C A T I O N   *************

 *************************************************************************/

 

 control MyVerifyChecksum(inout headers hdr, inout metadata meta) {  
 		apply {  }
 }

 /*************************************************************************
 **************  I N G R E S S   P R O C E S S I N G   *******************
 *************************************************************************/
 control MyIngress(inout headers hdr,
 									inout metadata meta,
 									inout standard_metadata_t standard_metadata) {
 		action drop() {
 				mark_to_drop(standard_metadata);
 		}

 		action forward(bit<9> port) {
 				standard_metadata.egress_spec = port;
 		}

 		table mac_forward {
 				key = {
 						hdr.ethernet.dstAddr: exact;
 				}

 				actions = {
 						forward;
 						drop;
 				}
 				size = 1024;
 				default_action = drop();
 		}

 		apply {
 				mac_forward.apply();
 		}
 }

 /*************************************************************************
 ****************  E G R E S S   P R O C E S S I N G   *******************
 *************************************************************************/

 control MyEgress(inout headers hdr,
 								inout metadata meta,
 								inout standard_metadata_t standard_metadata) {
 		apply {  }
 }

 /*************************************************************************
 *************   C H E C K S U M    C O M P U T A T I O N   **************
 *************************************************************************/

 control MyComputeChecksum(inout headers  hdr, inout metadata meta) {
 		apply {
 		}
 }

 /*************************************************************************
 ***********************  D E P A R S E R  *******************************
 *************************************************************************/

 control MyDeparser(packet_out packet, in headers hdr) {
 		apply {
 			packet.emit(hdr.ethernet);
 		}
 }

 /*************************************************************************
 ***********************  S W I T C H  *******************************
 *************************************************************************/

 V1Switch(
 MyParser(),
 MyVerifyChecksum(),
 MyIngress(),
 MyEgress(),
 MyComputeChecksum(),
 MyDeparser()

 ) main;
```

`cmd.txt`:

```
 table_add mac_forward forward 00:00:0a:00:01:01 => 1
 table_add mac_forward forward 00:00:0a:00:01:02 => 2
```

`p4run`

![](https://i.imgur.com/JNgst6b.png)

---

### MAC Layer Forwarding (HomeWork-1)

![](https://i.imgur.com/NNcDxLI.png)

`p4app.json`: 

```
{
  "program": "basic.p4",
  "switch": "simple_switch",
  "compiler": "p4c",
  "options": "--target bmv2 --arch v1model --std p4-16",
  "switch_cli": "simple_switch_CLI",
  "cli": true,
  "pcap_dump": true,
  "enable_log": true,
  "topo_module": {
    "file_path": "",
    "module_name": "p4utils.mininetlib.apptopo",
    "object_name": "AppTopoStrategies"
  },
  "controller_module": null,
  "topodb_module": {
    "file_path": "",
    "module_name": "p4utils.utils.topology",
    "object_name": "Topology"
  },
  "mininet_module": {
    "file_path": "",
    "module_name": "p4utils.mininetlib.p4net",
    "object_name": "P4Mininet"
  },
  "topology": {
    "assignment_strategy":"l2",
    "links": [["h1", "s1"], ["h2", "s2"], ["h3", "s3"], ["s1", "s2"], ["s2", "s3"]],
    "hosts": {
      "h1": {
      },
      "h2": {
      },
      "h3": {
      }
    },
    "switches": {
      "s1": {
        "cli_input": "cmd.txt",
        "program": "basic.p4"
      },
      "s2": {
        "cli_input": "cmd2.txt",
        "program": "basic.p4"
      },
      "s3": {
        "cli_input": "cmd3.txt",
        "program": "basic.p4"
      }
    }
  }
}
```

`basic.p4`

```
/* -*- P4_16 -*- */
#include <core.p4>
#include <v1model.p4>
/*************************************************************************
*********************** H E A D E R S  ***********************************
*************************************************************************/
header ethernet_t {
    bit<48> dstAddr;
    bit<48> srcAddr;
    bit<16>   etherType;
}
 
struct metadata {
    /* empty */
}
 
struct headers {
  ethernet_t   ethernet;
}
 
/*************************************************************************
*********************** P A R S E R  ***********************************
*************************************************************************/
parser MyParser(packet_in packet,
                out headers hdr,
                inout metadata meta,
                inout standard_metadata_t standard_metadata) {
    state start {
         transition parse_ethernet;
    }
     state parse_ethernet {
        packet.extract(hdr.ethernet);
        transition accept;
     }	
}
 
/*************************************************************************
************   C H E C K S U M    V E R I F I C A T I O N   *************
*************************************************************************/
 
control MyVerifyChecksum(inout headers hdr, inout metadata meta) {  
    apply {  }
}
/*************************************************************************
**************  I N G R E S S   P R O C E S S I N G   *******************
*************************************************************************/
control MyIngress(inout headers hdr,
                  inout metadata meta,
                  inout standard_metadata_t standard_metadata) {
    action drop() {
        mark_to_drop(standard_metadata);
    }
    action forward(bit<9> port) {
        standard_metadata.egress_spec = port;
    }
    table mac_forward {
        key = {
            hdr.ethernet.dstAddr: exact;
        }
        actions = {
            forward;
            drop;
        }
        size = 1024;
        default_action = drop();
    }
    apply {
        mac_forward.apply();
    }
}
/*************************************************************************
****************  E G R E S S   P R O C E S S I N G   *******************
*************************************************************************/
control MyEgress(inout headers hdr,
                 inout metadata meta,
                 inout standard_metadata_t standard_metadata) {
    apply {  }
}
/*************************************************************************
*************   C H E C K S U M    C O M P U T A T I O N   **************
*************************************************************************/
control MyComputeChecksum(inout headers  hdr, inout metadata meta) {
     apply {
    }
}
/*************************************************************************
***********************  D E P A R S E R  *******************************
*************************************************************************/
control MyDeparser(packet_out packet, in headers hdr) {
    apply {
      packet.emit(hdr.ethernet);
    }
}
/*************************************************************************
***********************  S W I T C H  *******************************
*************************************************************************/
V1Switch(
MyParser(),
MyVerifyChecksum(),
MyIngress(),
MyEgress(),
MyComputeChecksum(),
MyDeparser()
) main;
```

`cmd.txt`:

```
table_add mac_forward forward 00:00:0a:00:00:01 => 1
table_add mac_forward forward 00:00:0a:00:00:02 => 2
table_add mac_forward forward 00:00:0a:00:00:03 => 2
```

`cmd2.txt`: 

```
table_add mac_forward forward 00:00:0a:00:00:01 => 2
table_add mac_forward forward 00:00:0a:00:00:02 => 1
table_add mac_forward forward 00:00:0a:00:00:03 => 3
```

`cmd3.txt`:

```
table_add mac_forward forward 00:00:0a:00:00:01 => 2
table_add mac_forward forward 00:00:0a:00:00:02 => 2
table_add mac_forward forward 00:00:0a:00:00:03 => 1
```

`p4run`
![](https://i.imgur.com/8U58753.png)




---


## Network Layer Forwarding 

![](https://i.imgur.com/vc2ITKQ.png)

`p4app.json`:

```
 {

 	"program": "ip_forward.p4",

 	"switch": "simple_switch",

 	"compiler": "p4c",

 	"options": "--target bmv2 --arch v1model --std p4-16",

 	"switch_cli": "simple_switch_CLI",

 	"cli": true,

 	"pcap_dump": true,

 	"enable_log": true,

 	"topo_module": {

 		"file_path": "",

 		"module_name": "p4utils.mininetlib.apptopo",

 		"object_name": "AppTopoStrategies"

 	},

 	"controller_module": null,

 	"topodb_module": {

 		"file_path": "",

 		"module_name": "p4utils.utils.topology",

 		"object_name": "Topology"

 	},

 	"mininet_module": {

 		"file_path": "",

 		"module_name": "p4utils.mininetlib.p4net",

 		"object_name": "P4Mininet"

 	},

 	"topology": {

 		"assignment_strategy": "manual",

 		"auto_arp_tables": "true",

 		"auto_gw_arp": "true",

 		"links": [["h1", "s1"], ["h2", "s1"]],

 		"hosts": {

 			"h1": {

 				"ip": "10.0.1.1/24",

 				"gw": "10.0.1.254"

 			},

 			"h2": {

 				"ip": "10.0.2.1/24",

 			"gw": "10.0.2.254"

 			}

 		},

 		"switches": {

 			"s1": {

 				"cli_input": "cmd.txt",

 				"program": "ip_forward.p4"

 			}

 		}

 	}

 }
```

`ip_forwarding.p4`:

```
 #include <core.p4>

 #include <v1model.p4>

 typedef bit<48> macAddr_t;

 typedef bit<9> egressSpec_t;

 

 header arp_t {

 		bit<16> htype;

 		bit<16> ptype;

 		bit<8>  hlen;

 		bit<8>  plen;

 		bit<16> opcode;

 		bit<48> hwSrcAddr;

 		bit<32> protoSrcAddr;

 		bit<48> hwDstAddr;

 		bit<32> protoDstAddr;

 }

 

 header ethernet_t {

 		bit<48> dstAddr;

 		bit<48> srcAddr;

 		bit<16> etherType;

 }

 

 header ipv4_t {

 		bit<4>  version;

 		bit<4>  ihl;

 		bit<8>  diffserv;

 		bit<16> totalLen;

 		bit<16> identification;

 		bit<3>  flags;

 		bit<13> fragOffset;

 		bit<8>  ttl;

 		bit<8>  protocol;

 		bit<16> hdrChecksum;

 		bit<32> srcAddr;

 		bit<32> dstAddr;

 }

 

 struct metadata {

 }

 

 struct headers {

 		@name(".arp")

 		arp_t      arp;

 		@name(".ethernet")

 		ethernet_t ethernet;

 		@name(".ipv4")

 		ipv4_t     ipv4;

 }

 

 parser ParserImpl(packet_in packet, out headers hdr, inout metadata meta, inout standard_metadata_t standard_metadata) {

 		@name(".parse_arp") state parse_arp {

 				packet.extract(hdr.arp);

 				transition accept;

 		}

 		@name(".parse_ethernet") state parse_ethernet {

 				packet.extract(hdr.ethernet);

 				transition select(hdr.ethernet.etherType) {

 						16w0x800: parse_ipv4;

 						16w0x806: parse_arp;

 						default: accept;

 				}

 		}

 		@name(".parse_ipv4") state parse_ipv4 {

 				packet.extract(hdr.ipv4);

 				transition accept;

 		}

 		@name(".start") state start {

 				transition parse_ethernet;

 		}

 }

 

 control egress(inout headers hdr, inout metadata meta, inout standard_metadata_t standard_metadata) {

 		apply {

 		}

 }

 

 control ingress(inout headers hdr, inout metadata meta, inout standard_metadata_t standard_metadata) {

 		@name(".set_nhop") action set_nhop(macAddr_t dstAddr, egressSpec_t port) {

 				//set the src mac address as the previous dst, this is not correct right?

 				hdr.ethernet.srcAddr = hdr.ethernet.dstAddr;

 

 				//set the destination mac address that we got from the match in the table

 				hdr.ethernet.dstAddr = dstAddr;

 

 				//set the output port that we also get from the table

 				standard_metadata.egress_spec = port;

 

 				//decrease ttl by 1

 				hdr.ipv4.ttl = hdr.ipv4.ttl - 1;

 		}

 		@name("._drop") action _drop() {

 				mark_to_drop(standard_metadata);

 		}

 		@name(".ipv4_lpm") table ipv4_lpm {

 				actions = {

 						set_nhop;

 						_drop;

 				}

 				key = {

 						hdr.ipv4.dstAddr: lpm;

 				}

 				size = 512;

 				const default_action = _drop();

 		}

 		apply {

 				ipv4_lpm.apply();

 		}

 }

 

 control DeparserImpl(packet_out packet, in headers hdr) {

 		apply {

 				packet.emit(hdr.ethernet);

 				packet.emit(hdr.arp);

 				packet.emit(hdr.ipv4);

 		}

 }

 

 control verifyChecksum(inout headers hdr, inout metadata meta) {

 		apply {

 				verify_checksum(true, { hdr.ipv4.version, hdr.ipv4.ihl, hdr.ipv4.diffserv, hdr.ipv4.totalLen, hdr.ipv4.identification, hdr.ipv4.flags, hdr.ipv4.fragOffset, hdr.ipv4.ttl, hdr.ipv4.protocol, hdr.ipv4.srcAddr, hdr.ipv4.dstAddr }, hdr.ipv4.hdrChecksum, HashAlgorithm.csum16);

 		}

 }

 

 control computeChecksum(inout headers hdr, inout metadata meta) {

 		apply {

 				update_checksum(true, { hdr.ipv4.version, hdr.ipv4.ihl, hdr.ipv4.diffserv, hdr.ipv4.totalLen, hdr.ipv4.identification, hdr.ipv4.flags, hdr.ipv4.fragOffset, hdr.ipv4.ttl, hdr.ipv4.protocol, hdr.ipv4.srcAddr, hdr.ipv4.dstAddr }, hdr.ipv4.hdrChecksum, HashAlgorithm.csum16);

 		}

 }

 

 V1Switch(ParserImpl(), verifyChecksum(), ingress(), egress(), computeChecksum(), DeparserImpl()) main;
```

`cmd.txt`:

```
 table_add ipv4_lpm set_nhop 10.0.1.1/32 => 00:00:0a:00:01:01 1

 table_add ipv4_lpm set_nhop 10.0.2.1/32 => 00:00:0a:00:02:01 2
```
`p4run`

![](https://i.imgur.com/jnk8eKC.jpg)


### Network Layer Forwarding (homework 2)

`p4app.json`:

```
 {

 	"program": "ip_forward.p4",

 	"switch": "simple_switch",

 	"compiler": "p4c",

 	"options": "--target bmv2 --arch v1model --std p4-16",

 	"switch_cli": "simple_switch_CLI",

 	"cli": true,

 	"pcap_dump": true,

 	"enable_log": true,

 	"topo_module": {

 		"file_path": "",

 		"module_name": "p4utils.mininetlib.apptopo",

 		"object_name": "AppTopoStrategies"

 	},

 	"controller_module": null,

 	"topodb_module": {

 		"file_path": "",

 		"module_name": "p4utils.utils.topology",

 		"object_name": "Topology"

 	},

 	"mininet_module": {

 		"file_path": "",

 		"module_name": "p4utils.mininetlib.p4net",

 		"object_name": "P4Mininet"

 	},

 	"topology": {

 		"assignment_strategy": "l3",

 		"auto_arp_tables": "true",

 		"auto_gw_arp": "true",

 		"links": [["h1", "s1"], ["h2", "s2"], ["h3", "s3"], ["s1", "s2"], ["s2", "s3"]],

 		"hosts": {

 			"h1": {

 				"ip": "10.1.1.2/24",

 				"gw": "10.1.1.254"

 			},

 			"h2": {

 				"ip": "10.2.2.2/24",

 			"gw": "10.2.2.254"

 			},

 			"h3": {

 				"ip": "10.3.3.2/24",

 				"gw": "10.3.3.254"

 			}

 		},

 		"switches": {

 			"s1": {

 				"cli_input": "cmd.txt",

 				"program": "ip_forward.p4"

 			},

 			"s2": {

 				"cli_input": "cmd2.txt",

 				"program": "ip_forward.p4"

 			},

 			"s3": {

 				"cli_input": "cmd3.txt",

 				"program": "ip_forward.p4"

 			}

 		}

 	}

 }
```

`ip_forward.p4`

```
#include <core.p4>
#include <v1model.p4>
typedef bit<48> macAddr_t;
typedef bit<9> egressSpec_t;
 
header arp_t {
    bit<16> htype;
    bit<16> ptype;
    bit<8>  hlen;
    bit<8>  plen;
    bit<16> opcode;
    bit<48> hwSrcAddr;
    bit<32> protoSrcAddr;
    bit<48> hwDstAddr;
    bit<32> protoDstAddr;
}
 
header ethernet_t {
    bit<48> dstAddr;
    bit<48> srcAddr;
    bit<16> etherType;
}
 
header ipv4_t {
    bit<4>  version;
    bit<4>  ihl;
    bit<8>  diffserv;
    bit<16> totalLen;
    bit<16> identification;
    bit<3>  flags;
    bit<13> fragOffset;
    bit<8>  ttl;
    bit<8>  protocol;
    bit<16> hdrChecksum;
    bit<32> srcAddr;
    bit<32> dstAddr;
}
 
struct metadata {
}
 
struct headers {
    @name(".arp")
    arp_t      arp;
    @name(".ethernet")
    ethernet_t ethernet;
    @name(".ipv4")
    ipv4_t     ipv4;
}
 
parser ParserImpl(packet_in packet, out headers hdr, inout metadata meta, inout standard_metadata_t standard_metadata) {
    @name(".parse_arp") state parse_arp {
        packet.extract(hdr.arp);
        transition accept;
    }
    @name(".parse_ethernet") state parse_ethernet {
        packet.extract(hdr.ethernet);
        transition select(hdr.ethernet.etherType) {
            16w0x800: parse_ipv4;
            16w0x806: parse_arp;
            default: accept;
        }
    }
    @name(".parse_ipv4") state parse_ipv4 {
        packet.extract(hdr.ipv4);
        transition accept;
    }
    @name(".start") state start {
        transition parse_ethernet;
    }
}
 
control egress(inout headers hdr, inout metadata meta, inout standard_metadata_t standard_metadata) {
    apply {
    }
}
 
control ingress(inout headers hdr, inout metadata meta, inout standard_metadata_t standard_metadata) {
    @name(".set_nhop") action set_nhop(macAddr_t dstAddr, egressSpec_t port) {
        //set the src mac address as the previous dst, this is not correct right?
        hdr.ethernet.srcAddr = hdr.ethernet.dstAddr;
 
        //set the destination mac address that we got from the match in the table
        hdr.ethernet.dstAddr = dstAddr;
 
        //set the output port that we also get from the table
        standard_metadata.egress_spec = port;
 
        //decrease ttl by 1
        hdr.ipv4.ttl = hdr.ipv4.ttl - 1;
    }
    @name("._drop") action _drop() {
        mark_to_drop(standard_metadata);
    }
    @name(".ipv4_lpm") table ipv4_lpm {
        actions = {
            set_nhop;
            _drop;
        }
        key = {
            hdr.ipv4.dstAddr: lpm;
        }
        size = 512;
        const default_action = _drop();
    }
    apply {
        ipv4_lpm.apply();
    }
}
 
control DeparserImpl(packet_out packet, in headers hdr) {
    apply {
        packet.emit(hdr.ethernet);
        packet.emit(hdr.arp);
        packet.emit(hdr.ipv4);
    }
}
 
control verifyChecksum(inout headers hdr, inout metadata meta) {
    apply {
        verify_checksum(true, { hdr.ipv4.version, hdr.ipv4.ihl, hdr.ipv4.diffserv, hdr.ipv4.totalLen, hdr.ipv4.identification, hdr.ipv4.flags, hdr.ipv4.fragOffset, hdr.ipv4.ttl, hdr.ipv4.protocol, hdr.ipv4.srcAddr, hdr.ipv4.dstAddr }, hdr.ipv4.hdrChecksum, HashAlgorithm.csum16);
    }
}
 
control computeChecksum(inout headers hdr, inout metadata meta) {
    apply {
        update_checksum(true, { hdr.ipv4.version, hdr.ipv4.ihl, hdr.ipv4.diffserv, hdr.ipv4.totalLen, hdr.ipv4.identification, hdr.ipv4.flags, hdr.ipv4.fragOffset, hdr.ipv4.ttl, hdr.ipv4.protocol, hdr.ipv4.srcAddr, hdr.ipv4.dstAddr }, hdr.ipv4.hdrChecksum, HashAlgorithm.csum16);
    }
}
 
V1Switch(ParserImpl(), verifyChecksum(), ingress(), egress(), computeChecksum(), DeparserImpl()) main;
```

`cmd.txt`:

```
table_add ipv4_lpm set_nhop 10.1.1.2/32 => 00:00:0a:01:01:02 1
table_add ipv4_lpm set_nhop 10.2.2.2/32 => 00:00:0a:02:02:02 2
table_add ipv4_lpm set_nhop 10.3.3.2/32 => 00:00:0a:03:03:02 2
```

`cmd2.txt`:

```
table_add ipv4_lpm set_nhop 10.1.1.2/32 => 00:00:0a:01:01:02 2
table_add ipv4_lpm set_nhop 10.2.2.2/32 => 00:00:0a:02:02:02 1
table_add ipv4_lpm set_nhop 10.3.3.2/32 => 00:00:0a:03:03:02 3
```

`cmd3.txt`:

```
table_add ipv4_lpm set_nhop 10.1.1.2/32 => 00:00:0a:01:01:02 2
table_add ipv4_lpm set_nhop 10.2.2.2/32 => 00:00:0a:02:02:02 2
table_add ipv4_lpm set_nhop 10.3.3.2/32 => 00:00:0a:03:03:02 1
```

`p4run`:

![](https://i.imgur.com/AEsHhDJ.jpg)

### Network Layer Forwarding (HomeWork-2)

![](https://i.imgur.com/HmspjMV.png)


`p4app.json`:

```
{
  "program": "ip_forward.p4",
  "switch": "simple_switch",
  "compiler": "p4c",
  "options": "--target bmv2 --arch v1model --std p4-16",
  "switch_cli": "simple_switch_CLI",
  "cli": true,
  "pcap_dump": true,
  "enable_log": true,
  "topo_module": {
    "file_path": "",
    "module_name": "p4utils.mininetlib.apptopo",
    "object_name": "AppTopoStrategies"
  },
  "controller_module": null,
  "topodb_module": {
    "file_path": "",
    "module_name": "p4utils.utils.topology",
    "object_name": "Topology"
  },
  "mininet_module": {
    "file_path": "",
    "module_name": "p4utils.mininetlib.p4net",
    "object_name": "P4Mininet"
  },
  "topology": {
    "assignment_strategy": "mixed",
    "auto_arp_tables": "true",
    "auto_gw_arp": "true",
    "links": [["h1", "s1"], ["h2", "s3"], ["h3", "s3"], ["s1", "s2"], ["s2", "s3"]],
    "hosts": {
      "h1": {
      },
      "h2": {
      },
      "h3": {
      }
    },
    "switches": {
      "s1": {
        "cli_input": "cmd.txt",
        "program": "ip_forward.p4"
      },
      "s2": {
        "cli_input": "cmd2.txt",
        "program": "ip_forward.p4"
      },
      "s3": {
        "cli_input": "cmd3.txt",
        "program": "ip_forward.p4"
      }
    }
  }
}
```

`ip_forward.p4`

```
{
  "program": "ip_forward.p4",
  "switch": "simple_switch",
  "compiler": "p4c",
  "options": "--target bmv2 --arch v1model --std p4-16",
  "switch_cli": "simple_switch_CLI",
  "cli": true,
  "pcap_dump": true,
  "enable_log": true,
  "topo_module": {
    "file_path": "",
    "module_name": "p4utils.mininetlib.apptopo",
    "object_name": "AppTopoStrategies"
  },
  "controller_module": null,
  "topodb_module": {
    "file_path": "",
    "module_name": "p4utils.utils.topology",
    "object_name": "Topology"
  },
  "mininet_module": {
    "file_path": "",
    "module_name": "p4utils.mininetlib.p4net",
    "object_name": "P4Mininet"
  },
  "topology": {
    "assignment_strategy": "mixed",
    "auto_arp_tables": "true",
    "auto_gw_arp": "true",
    "links": [["h1", "s1"], ["h2", "s3"], ["h3", "s3"], ["s1", "s2"], ["s2", "s3"]],
    "hosts": {
      "h1": {
      },
      "h2": {
      },
      "h3": {
      }
    },
    "switches": {
      "s1": {
        "cli_input": "cmd.txt",
        "program": "ip_forward.p4"
      },
      "s2": {
        "cli_input": "cmd2.txt",
        "program": "ip_forward.p4"
      },
      "s3": {
        "cli_input": "cmd3.txt",
        "program": "ip_forward.p4"
      }
    }
  }
}
```

`cmd.txt`

```
table_add ipv4_lpm set_nhop 10.0.1.1/32 => 00:00:0a:00:01:01 1
table_add ipv4_lpm set_nhop 10.0.3.2/32 => 00:00:0a:00:03:02 2
table_add ipv4_lpm set_nhop 10.0.3.3/32 => 00:00:0a:00:03:03 2
```

`cmd2.txt`

```
table_add ipv4_lpm set_nhop 10.0.1.1/32 => 00:00:0a:00:01:01 1
table_add ipv4_lpm set_nhop 10.0.3.2/32 => 00:00:0a:00:03:02 2
table_add ipv4_lpm set_nhop 10.0.3.3/32 => 00:00:0a:00:03:03 2
```

`cmd3.txt`
```
table_add ipv4_lpm set_nhop 10.0.1.1/32 => 00:00:0a:00:01:01 3
table_add ipv4_lpm set_nhop 10.0.3.2/32 => 00:00:0a:00:03:02 1
table_add ipv4_lpm set_nhop 10.0.3.3/32 => 00:00:0a:00:03:03 2
```

`p4run`:

![](https://i.imgur.com/jcBg23c.png)

---

## Reference

1. https://www.youtube.com/watch?v=rOODoTlnKtI&feature=emb_title