MODBUS

MODBUS Protocol

Modicon Communication Bus (MODBUS) is an application layer protocol for client-server communication between a switch (server) and a device in the network running MODBUS client software (client). You can use MODBUS over a serial line to connect a computer to a remote terminal unit (RTU) in supervisory control and data acquisition (SCADA) systems.

MODBUS also runs on Ethernet TCP/IP networks. Use MODBUS TCP over an Ethernet network when connecting the switch to devices such as intelligent electronic devices (IEDs), distributed controllers, substation routers, IP phones, Wireless Access Points, and other network devices such as redundant substation switches.

The client can be an IED or a human machine interface (HMI) application that remotely configures and manages devices running MODBUS TCP. The switch functions as the server.

The switch encapsulates a request or response message in a MODBUS TCP application data unit (ADU). A client sends a message to a TCP port on the switch.


Note

MODBUS is supported only on standalone Cisco Catalyst IE9300 Rugged Series Switches.

Cisco Catalyst IE9300 MODBUS TCP Registers

This document lists the read-only registers for IE9300 switches. MODBUS clients use them to communicate with a MODBUS server (the switch). There are no writable registers.

System Information Registers

Address spaces 0x0800 through 0x0FFF are system information read-only registers. These 2048 registers are accessible by MODBUS function code 0x03 Read Multiple Registers.

Table 1. System Information Registers
Address Number of Registers Description R/W Format
0x0800 64 Product ID R Text
0x0840 64 Software image name R Text
0x0880 64 Software image version R Text
0x08C0 64 Host Name R Text
0x0900 1 Number of Gigabit Ethernet ports R Uint 16
0x0901 1 Number of 10 Gigabit Ethernet ports R Uint 16
0x0902 1 Number of mgig Ethernet ports R Uint 16
0x0903 1 Number of power supplies R Uint 16
0x0904 1 Power supply 1 status R Uint 16
0x0905 1 Power supply 2 status R Uint 16
0x0906 1 System or sensor ID 0 temperature R Uint 16

Port Information Registers

Address spaces 0x1000 through 0x3FFF are port information read-only registers. These 12,000 registers are accessible by MODBUS function code 0x03 Read Multiple Registers. They are updated every time upon receiving a read request to the register(s).

The following table shows the memory map for all interface registers, with 64-bit counters (Address space 0x1000 through 0x2FFF, 8,000 registers).

Table 2. Values for Getting Generic Port Information

Address

Number of Registers

Description

R/W

Format

0x1000

 64

LAN Port 1 name

R

Text

0x1040

64

LAN Port 2 name

R

Text

0x1080

64

LAN Port 3 name

R

Text

0x10C0

64

LAN Port 4 name

R

Text

0x1100

64

LAN Port 5 name

R

Text

0x1140

64

LAN Port 6 name

R

Text

0x1180

64

LAN Port 7 name

R

Text

0x11C0

64

LAN Port 8 name

R

Text

0x1200

64

LAN Port 9 name

R

Text

0x1240

64

LAN Port 10 name

R

Text

0x1280

64

LAN Port 11 name

R

Text

0x12C0

64

LAN Port 12 name

R

Text

0x1300

64

LAN Port 13 name

R

Text

0x1340

64

LAN Port 14 name

R

Text

0x1380

64

LAN Port 15 name

R

Text

0x13C0

64

LAN Port 15 name

R

Text

0x13C0

64

LAN Port 16 name

R

Text

0x1400

64

LAN Port 17 name

R

Text

0x1440

64

LAN Port 18 name

R

Text

0x1480

64

LAN Port 19 name

R

Text

0x14C0

64

LAN Port 20 name

R

Text

0x1500

64

LAN Port 21 name

R

Text

0x1540

64

LAN Port 22 name

R

Text

0x1580

64

LAN Port 23 name

R

Text

0x15C0

64

LAN Port 24 name

R

Text

0x1600

64

LAN Port 25 name

R

Text

0x1640

64

LAN Port 26 name

R

Text

0x1680

64

LAN Port 27 name

R

Text

0x16C0

64

LAN Port 28 name

R

Text

0x1700

1

LAN Port 1 state

R

Uint16

0x1701

1

LAN Port 2 state

R

Uint16

0x1702

1

LAN Port 3 state

R

Uint16

0x1703

1

LAN Port 4 state

R

Uint16

0x1704

1

LAN Port 5 state

R

Uint16

0x1705

1

LAN Port 6 state

R

Uint16

0x1706

1

LAN Port 7 state

R

Uint16

0x1707

1

LAN Port 8 state

R

Uint16

0x1708

1

LAN Port 9 state

R

Uint16

0x1709

1

LAN Port 10 state

R

Uint16

0x170A

1

LAN Port 11 state

R

Uint16

0x170B

1

LAN Port 12 state

R

Uint16

0x170C

1

LAN Port 13 state

R

Uint16

0x170D

1

LAN Port 14 state

R

Uint16

0x170E

1

LAN Port 15 state

R

Uint16

0x170F

1

LAN Port 16 state

R

Uint16

0x1710

1

LAN Port 17 state

R

Uint16

0x1711

1

LAN Port 18 state

R

Uint16

0x1712

1

LAN Port 19 state

R

Uint16

0x1713

1

LAN Port 20 state

R

Uint16

0x1714

1

LAN Port 21 state

R

Uint16

0x1715

1

LAN Port 22 state

R

Uint16

0x1716

1

LAN Port 23 state

R

Uint16

0x1717

1

LAN Port 24 state

R

Uint16

0x1718

1

LAN Port 25 state

R

Uint16

0x1719

1

LAN Port 26 state

R

Uint16

0x171A

1

LAN Port 27 state

R

Uint16

0x171B

1

LAN Port 28 state

R

Uint16
Table 3. Values for Getting Port Information Using 64-bit Counters

Address

Number of Registers

Description

R/W

Format

0x171C

4

LAN Port 1 statistics—number of packets received

R

Uint64

0x1720

4

LAN Port 2 statistics—number of packets received

R

Uint64

0x1724

4

LAN Port 3 statistics—number of packets received

R

Uint64

0x1728

4

LAN Port 4 statistics—number of packets received

R

Uint64

0x172C

4

LAN Port 5 statistics—number of packets received

R

Uint64

0x1730

4

LAN Port 6 statistics—number of packets received

R

Uint64

0x1734

4

LAN Port 7 statistics—number of packets received

R

Uint64

0x1738

4

LAN Port 8 statistics—number of packets received

R

Uint64

0x173C

4

LAN Port 9 statistics—number of packets received

R

Uint64

0x1740

4

LAN Port 10 statistics—number of packets received

R

Uint64

0x1744

4

LAN Port 11 statistics—number of packets received

R

Uint64

0x1748

4

LAN Port 12 statistics—number of packets received

R

Uint64

0x174C

4

LAN Port 13 statistics—number of packets received

R

Uint64

0x1750

4

LAN Port 14 statistics—number of packets received

R

Uint64

0x1754

4

LAN Port 15 statistics—number of packets received

R

Uint64

0x1758

4

LAN Port 16 statistics—number of packets received

R

Uint64

0x175C

4

LAN Port 17 statistics—number of packets received

R

Uint64

0x1760

4

LAN Port 18 statistics—number of packets received

R

Uint64

0x1764

4

LAN Port 19 statistics—number of packets received

R

Uint64

0x1768

4

LAN Port 20 statistics—number of packets received

R

Uint64

0x176C

4

LAN Port 21 statistics—number of packets received

R

Uint64

0x1770

4

LAN Port 22 statistics—number of packets received

R

Uint64

0x1774

4

LAN Port 23 statistics—number of packets received

R

Uint64

0x1778

4

LAN Port 24 statistics—number of packets received

R

Uint64

0x177C

4

LAN Port 25 statistics—number of packets received

R

Uint64

0x1780

4

LAN Port 26 statistics—number of packets received

R

Uint64

0x1784

4

LAN Port 27 statistics—number of packets received

R

Uint64

0x1788

4

LAN Port 28 statistics—number of packets received

R

Uint64

0x178C

4

LAN Port 1 statistics—number of packets sent

R

Uint64

0x1790

4

LAN Port 2 statistics—number of packets sent

R

Uint64

0x1794

4

LAN Port 3 statistics—number of packets sent

R

Uint64

0x1798

4

LAN Port 4 statistics—number of packets sent

R

Uint64

0x179C

4

LAN Port 5 statistics—number of packets sent

R

Uint64

0x17A0

4

LAN Port 6 statistics—number of packets sent

R

Uint64

0x17A4

4

LAN Port 7 statistics—number of packets sent

R

Uint64

0x17A8

4

LAN Port 8 statistics—number of packets sent

R

Uint64

0x17AC

4

LAN Port 9 statistics—number of packets sent

R

Uint64

0x17B0

4

LAN Port 10 statistics—number of packets sent

R

Uint64

0x17B4

4

LAN Port 11 statistics—number of packets sent

R

Uint64

0x17B8

4

LAN Port 12 statistics—number of packets sent

R

Uint64

0x17BC

4

LAN Port 13 statistics—number of packets sent

R

Uint64

0x17C0

4

LAN Port 14 statistics—number of packets sent

R

Uint64

0x17C4

4

LAN Port 15 statistics—number of packets sent

R

Uint64

0x17C8

4

LAN Port 16 statistics—number of packets sent

R

Uint64
0x17CC

4

LAN Port 17 statistics—number of packets sent

R

Uint64

0x17D0

4

LAN Port 18 statistics—number of packets sent

R

Uint64

0x17D4

4

LAN Port 19 statistics—number of packets sent

R

Uint64

0x17D8

4

LAN Port 20 statistics—number of packets sent

R

Uint64

0x17DC

4

LAN Port 21 statistics—number of packets sent

R

Uint64

0x17E0

4

LAN Port 22 statistics—number of packets sent

R

Uint64

0x17E4

4

LAN Port 23 statistics—number of packets sent

R

Uint64

0x17E8

4

LAN Port 24 statistics—number of packets sent

R

Uint64

0x17EC

4

LAN Port 25 statistics—number of packets sent

R

Uint64

0x17F0

4

LAN Port 26 statistics—number of packets sent

R

Uint64

0x17F4

4

LAN Port 27 statistics—number of packets sent

R

Uint64

0x17F8

4

LAN Port 28 statistics—number of packets sent

R

Uint64

0x17FC

4

LAN Port 1 statistics—number of bytes received

R

Uint64

0x1800

4

LAN Port 2 statistics—number of bytes received

R

Uint64

0x1804

4

LAN Port 3 statistics—number of bytes received

R

Uint64

0x1808

4

LAN Port 4 statistics—number of bytes received

R

Uint64

0x180C

4

LAN Port 5 statistics—number of bytes received

R

Uint64

0x1810

4

LAN Port 6 statistics—number of bytes received

R

Uint64

0x1814

4

LAN Port 7 statistics—number of bytes received

R

Uint64

0x1818

4

LAN Port 8 statistics—number of bytes received

R

Uint64

0x181C

4

LAN Port 9 statistics—number of bytes received

R

Uint64

0x1820

4

LAN Port 10 statistics—number of bytes received

R

Uint64

0x1824

4

LAN Port 11 statistics—number of bytes received

R

Uint64

0x1828

4

LAN Port 12 statistics—number of bytes received

R

Uint64

0x182C

4

LAN Port 13 statistics—number of bytes received

R

Uint64

0x1830

4

LAN Port 14 statistics—number of bytes received

R

Uint64

0x1834

4

LAN Port 15 statistics—number of bytes received

R

Uint64

0x1838

4

LAN Port 16 statistics—number of bytes received

R

Uint64

0x183C

4

LAN Port 17 statistics—number of bytes received

R

Uint64

0x1840

4

LAN Port 18 statistics—number of bytes received

R

Uint64

0x1844

4

LAN Port 19 statistics—number of bytes received

R

Uint64

0x1848

4

LAN Port 20 statistics—number of bytes received

R

Uint64

0x184C

4

LAN Port 21 statistics—number of bytes received

R

Uint64

0x1850

4

LAN Port 22 statistics—number of bytes received

R

Uint64

0x1854

4

LAN Port 23 statistics—number of bytes received

R

Uint64

0x1858

4

LAN Port 24 statistics—number of bytes received

R

Uint64

0x185C

4

LAN Port 25 statistics—number of bytes received

R

Uint64

0x1860

4

LAN Port 26 statistics—number of bytes received

R

Uint64

0x1864

4

LAN Port 27 statistics—number of bytes received

R

Uint64

0x1868

4

LAN Port 28 statistics—number of bytes received

R

Uint64

0x186C

4

LAN Port 1 statistics—number of bytes sent

R

Uint64

0x1870

4

LAN Port 2 statistics—number of bytes sent

R

Uint64

0x1874

4

LAN Port 3 statistics—number of bytes sent

R

Uint64

0x1878

4

LAN Port 4 statistics—number of bytes sent

R

Uint64

0x187C

4

LAN Port 5 statistics—number of bytes sent

R

Uint64

0x1880

4

LAN Port 6 statistics—number of bytes sent

R

Uint64

0x1884

4

LAN Port 7 statistics—number of bytes sent

R

Uint64

0x1888

4

LAN Port 8 statistics—number of bytes sent

R

Uint64

0x188C

4

LAN Port 9 statistics—number of bytes sent

R

Uint64

0x1890

4

LAN Port 10 statistics—number of bytes sent

R

Uint64

0x1894

4

LAN Port 11 statistics—number of bytes sent

R

Uint64

0x1898

4

LAN Port 12 statistics—number of bytes sent

R

Uint64

0x189C

4

LAN Port 13 statistics—number of bytes sent

R

Uint64

0x18A0

4

LAN Port 14 statistics—number of bytes sent

R

Uint64

0x18A4

4

LAN Port 15 statistics—number of bytes sent

R

Uint64

0x18A8

4

LAN Port 16 statistics—number of bytes sent

R

Uint64

0x18AC

4

LAN Port 17 statistics—number of bytes sent

R

Uint64

0x18B0

4

LAN Port 18 statistics—number of bytes sent

R

Uint64

0x18B4

4

LAN Port 19 statistics—number of bytes sent

R

Uint64

0x18B8

4

LAN Port 20 statistics—number of bytes sent

R

Uint64

0x18BC

4

LAN Port 21 statistics—number of bytes sent

R

Uint64

0x18C0

4

LAN Port 22 statistics—number of bytes sent

R

Uint64

0x18C4

4

LAN Port 23 statistics—number of bytes sent

R

Uint64

0x18C8

4

LAN Port 24 statistics—number of bytes sent

R

Uint64

0x18CC

4

LAN Port 25 statistics—number of bytes sent

R

Uint64

0x18D0

4

LAN Port 26 statistics—number of bytes sent

R

Uint64

0x18D4

4

LAN Port 27 statistics—number of bytes sent

R

Uint64

0x18D8

4

LAN Port 28 statistics—number of bytes sent

R

Uint64
Table 4. Values for Getting Port Information Using 32-bit Counters

Address

Number of Registers

Description

R/W

Format

0x18DC

2

LAN Port 1 statistics—number of packets received

R

Uint32

0x18DE

2

LAN Port 2 statistics—number of packets received

R

Uint32

0x18E0

2

LAN Port 3 statistics—number of packets received

R

Uint32

0x18E2

2

LAN Port 4 statistics—number of packets received

R

Uint32

0x18E4

2

LAN Port 5 statistics—number of packets received

R

Uint32

0x18E6

2

LAN Port 6 statistics—number of packets received

R

Uint32

0x18E8

2

LAN Port 7 statistics—number of packets received

R

Uint32

0x18EA

2

LAN Port 8 statistics—number of packets received

R

Uint32

0x18EC

2

LAN Port 9 statistics—number of packets received

R

Uint32

0x18EE

2

LAN Port 10 statistics—number of packets received

R

Uint32

0x18F0

2

LAN Port 11 statistics—number of packets received

R

Uint32

0x18F2

2

LAN Port 12 statistics—number of packets received

R

Uint32

0x18F4

2

LAN Port 13 statistics—number of packets received

R

Uint32

0x18F6

2

LAN Port 14 statistics—number of packets received

R

Uint32

0x18F8

2

LAN Port 15 statistics—number of packets received

R

Uint32

0x18FA

2

LAN Port 16 statistics—number of packets received

R

Uint32
0x18FC

2

LAN Port 17 statistics—number of packets received

R

Uint32

0x18FE

2

LAN Port 18 statistics—number of packets received

R

Uint32

0x1900

2

LAN Port 19 statistics—number of packets received

R

Uint32

0x1902

2

LAN Port 20 statistics—number of packets received

R

Uint32

0x1904

2

LAN Port 21 statistics—number of packets received

R

Uint32

0x1906

2

LAN Port 22 statistics—number of packets received

R

Uint32

0x1908

2

LAN Port 23 statistics—number of packets received

R

Uint32

0x190A

2

LAN Port 24 statistics—number of packets received

R

Uint32

0x190C

2

LAN Port 25 statistics—number of packets received

R

Uint32

0x190E

2

LAN Port 26 statistics—number of packets received

R

Uint32

0x1910

2

LAN Port 27 statistics—number of packets received

R

Uint32

0x1912

2

LAN Port 28 statistics—number of packets received

R

Uint32

0x1914

2

LAN Port 1 statistics—number of packets sent

R

Uint32

0x1916

2

LAN Port 3 statistics—number of packets sent

Uint32

0x1918

2

LAN Port 3 statistics—number of packets sent

R

Uint32

0x191A

2

LAN Port 4 statistics—number of packets sent

R

Uint32

0x191C

2

LAN Port 5 statistics—number of packets sent

R

Uint32

0x191E

2

LAN Port 6 statistics—number of packets sent

R

Uint32

0x1920

2

LAN Port 7 statistics—number of packets sent

R

Uint32

0x1922

2

LAN Port 8 statistics—number of packets sent

R

Uint32

0x1924

2

LAN Port 9 statistics—number of packets sent

R

Uint32

0x1926

2

LAN Port 10 statistics—number of packets sent

R

Uint32

0x1928

2

LAN Port 11 statistics—number of packets sent

R

Uint32

0x192A

2

LAN Port 12 statistics—number of packets sent

R

Uint32

0x192C

2

LAN Port 13 statistics—number of packets sent

R

Uint32

0x192E

2

LAN Port 14 statistics—number of packets sent

R

Uint32

0x1930

2

LAN Port 15 statistics—number of packets sent

R

Uint32

0x1932

2

LAN Port 16 statistics—number of packets sent

R

Uint32

0x1934

2

LAN Port 17 statistics—number of packets sent

R

Uint32

0x1936

2

LAN Port 18 statistics—number of packets sent

R

Uint32

0x1938

2

LAN Port 19 statistics—number of packets sent

R

Uint32

0x193A

2

LAN Port 20 statistics—number of packets sent

R

Uint32

0x193C

2

LAN Port 21 statistics—number of packets sent

R

Uint32

0x193E

2

LAN Port 22 statistics—number of packets sent

R

Uint32

0x1940

2

LAN Port 23 statistics—number of packets sent

R

Uint32

0x1942

2

LAN Port 24 statistics—number of packets sent

R

Uint32

0x1944

2

LAN Port 25 statistics—number of packets sent

R

Uint32

0x1946

2

LAN Port 26 statistics—number of packets sent

R

Uint32

0x1948

2

LAN Port 27 statistics—number of packets sent

R

Uint32

0x194A

2

LAN Port 28 statistics—number of packets sent

R

Uint32

0x194C

2

LAN Port 1 statistics—number of bytes received

R

Uint32

0x194E

2

LAN Port 2 statistics—number of bytes received

R

Uint32

0x1950

2

LAN Port 3 statistics—number of bytes received

R

Uint32

0x1952

2

LAN Port 4 statistics—number of bytes received

R

Uint32

0x1954

2

LAN Port 5 statistics—number of bytes received

R

Uint32

0x1956

2

LAN Port 6 statistics—number of bytes received

R

Uint32

0x1958

2

LAN Port 7 statistics—number of bytes received

R

Uint32

0x195A

2

LAN Port 8 statistics—number of bytes received

R

Uint32

0x195C

2

LAN Port 9 statistics—number of bytes received

R

Uint32

0x195E

2

LAN Port 10 statistics—number of bytes received

R

Uint32

0x1960

2

LAN Port 11 statistics—number of bytes received

R

Uint32

0x1962

2

LAN Port 12 statistics—number of bytes received

R

Uint32

0x1964

2

LAN Port 13 statistics—number of bytes received

R

Uint32

0x1966

2

LAN Port 14 statistics—number of bytes received

R

Uint32

0x1968

2

LAN Port 15 statistics—number of bytes received

R

Uint32

0x196A

2

LAN Port 16 statistics—number of bytes received

R

Uint32

0x196C

2

LAN Port 17 statistics—number of bytes received

R

Uint32

0x196E

2

LAN Port 18 statistics—number of bytes received

R

Uint32

0x1970

2

LAN Port 19 statistics—number of bytes received

R

Uint32

0x1972

2

LAN Port 20 statistics—number of bytes received

R

Uint32

0x1974

2

LAN Port 21 statistics—number of bytes received

R

Uint32

0x1976

2

LAN Port 22 statistics—number of bytes received

R

Uint32

0x1978

2

LAN Port 23 statistics—number of bytes received

R

Uint32

0x197A

2

LAN Port 24 statistics—number of bytes received

R

Uint32

0x197C

2

LAN Port 25 statistics—number of bytes received

R

Uint32

0x197E

2

LAN Port 26 statistics—number of bytes received

R

Uint32

0x1980

2

LAN Port 27 statistics—number of bytes received

R

Uint32

0x1982

2

LAN Port 28 statistics—number of bytes received

R

Uint32
0x1984 2 LAN Port 1 Statistics – Number of bytes sent R Uint32
0x1986 2 LAN Port 2 Statistics – Number of bytes sent R Uint32
0x1988 2 LAN Port 3 Statistics – Number of bytes sent R Uint32

0x198A

2

LAN Port 4 statistics—number of bytes sent

R

Uint32

0x198C

2

LAN Port 5 statistics—number of bytes sent

R

Uint32

0x198E

2

LAN Port 6 statistics—number of bytes sent

R

Uint32

0x1990

2

LAN Port 7 statistics—number of bytes sent

R

Uint32

0x1992

2

LAN Port 8 statistics—number of bytes sent

R

Uint32

0x1994

2

LAN Port 9 statistics—number of bytes sent

R

Uint32

0x1996

2

LAN Port 10 statistics—number of bytes sent

R

Uint32

0x1998

2

LAN Port 11 statistics—number of bytes sent

R

Uint32

0x199A

2

LAN Port 12 statistics—number of bytes sent

R

Uint32

0x199C

2

LAN Port 13 statistics—number of bytes sent

R

Uint32

0x199E

2

LAN Port 14 statistics—number of bytes sent

R

Uint32

0x19A0

2

LAN Port 15 statistics—number of bytes sent

R

Uint32

0x19A2

2

LAN Port 16 statistics—number of bytes sent

R

Uint32

0x19A4

2

LAN Port 17 statistics—number of bytes sent

R

Uint32

0x19A6

2

LAN Port 18 statistics—number of bytes sent

R

Uint32

0x19A8

2

LAN Port 19 statistics—number of bytes sent

R

Uint32

0x19AA

2

LAN Port 20 statistics—number of bytes sent

R

Uint32

0x19AC

2

LAN Port 21 statistics—number of bytes sent

R

Uint32

0x19AE

2

LAN Port 22 statistics—number of bytes sent

R

Uint32

0x19B0

2

LAN Port 23 statistics—number of bytes sent

R

Uint32

0x19B2

2

LAN Port 24 statistics—number of bytes sent

R

Uint32

0x19B4

2

LAN Port 25 statistics—number of bytes sent

R

Uint32

0x19B6

2

LAN Port 26 statistics—number of bytes sent

R

Uint32

0x19B8

2

LAN Port 27 statistics—number of bytes sent

R

Uint32

0x19BA

2

LAN Port 28 statistics—number of bytes sent

R

Uint32

Interpreting the Port State Value

This section provides information for determining the port state.

In the following table, the upper byte repressents the interface state, and the lower byte represents the line protocol state.

Address

Description

Value

0x1700 to 0x171B

Port state information

Upper byte:

  • 0x0: Interface is down

  • 0x1: Interface is going down

  • 0x2: Interface is in the initializing state

  • 0x3: Interface is coming up

  • 0x4: Interface is up and running

  • 0x5: Interface is reset by the user

  • 0x6: Interface is shut down by the user

  • 0x7: Interface is being deleted

The lower byte:

  • 0x0: Line protocol state is down

  • 0x1: Line protocol state is up

Configure MODBUS

The MODBUS TCP server listens for MODBUS client requests on TCP port 502 by default. Port 502 is enabled when MODBUS server is started unless you configure a different port for MODBUS communications. The MODBUS server is disabled by default.


Note

MODBUS is supported only on standalone Cisco Catalyst IE9300 Rugged Series Switches.

To configure MODBUS:

Before you begin

If a firewall or other security services are enabled, the switch TCP port might be blocked, and the switch and the client cannot communicate. If a firewall and other security services are disabled, a denial-of-service attack might occur on the switch. To add security when using MODBUS TCP, configure an ACL to permit traffic from specific clients or configure QoS to rate-limit traffic.

Procedure

Step 1

Enter global configuration mode:

configure terminal

Step 2

Enable MODBUS TCP on the switch:

scada modbus tcp server

To disable MODBUS on the switch and return to the default settings, enter the no scada modbus tcp server global configuration command.

The system displays a message to warn you that starting the MODBUS TCP server is a security risk:

WARNING: Starting Modbus TCP server is a security risk. Please understand the security issues involved before proceeding further. Do you still want to start the server? [yes/no]:

Step 3

Enter yes to confirm that you understand the security issues and to proceed with starting the server.

Step 4

(Optional) Set the TCP port to which clients send messages:

scada modbus tcp server port tcp-port-number

The range for tcp-port-number is 1 to 65535. The default is 502.

Step 5

(Optional) Set the number of simultaneous connection requests sent to the switch:

scada modbus tcp server connection connection-requests

The range for connection-requests is 1 to 5. The default is 1.

Step 6

Return to privileged EXEC mode:

end

Example

Switch# configure terminal
Switch(config)# scada modbus tcp server
WARNING: Starting Modbus TCP server is a security risk. Please understand the security issues involved 
before proceeding further. Do you still want to start the server? [yes/no]: y
Switch(config)# end

Displaying MODBUS Commands

Use the commands listed below to display information for MODBUS TCP.

Command

Purpose

show scada modbus tcp server

Displays the server information and statistics

show scada modbus tcp server connections

Shows information and statistics for each client connection

clear scada modbus tcp server statistics

Clears all the statistics for the Modbus server, including statistics for each client connection

The following is an example of the show scada modbus tcp server command and its output: 

Switch# show scada modbus tcp server
Summary: enabled, running, process id 142
Conn Stats: listening on port 801, 4 max simultaneous connections
    0 current client connections
    0 total accepted connections, 0 accept connection errors
    0 closed connections, 0 close connection errors
Send Stats: 0 tcp msgs sent, 0 tcp bytes sent, 0 tcp errors
    0 responses sent, 0 exceptions sent, 0 send errors
Recv Stats: 0 tcp msgs received, 0 tcp bytes received, 0 tcp errors
    0 requests received, 0 receive errors

Feature History

The following table provides release and related information for the features that are documented in this guide. The features are available in all the releases after the one they were introduced in, unless noted otherwise.

Release

Feature

Feature Information

Cisco IOS XE Dublin 17.12.1

MODBUS

Beginning in this release, Cisco Catalyst IE9300 Rugged Series Switches are supported for Modicon Communication Bus (MODBUS).