The chassis has one Gigabit Ethernet Management Ethernet interface on each Route Switch Processor.

The purpose of this interface is to allow users to perform management tasks on the router; it is basically an interface that should not and often cannot forward network traffic but can otherwise access the router, often via Telnet and SSH, and perform most management tasks on the router. The interface is most useful before a router has begun routing, or in troubleshooting scenarios when the interfaces are inactive.

The following aspects of the Management Ethernet interface should be noted:

• Each RSP has a Management Ethernet interface, but only the active RSP has an accessible Management Ethernet interface (the standby RSP can be accessed using the console port, however).
• IPv4, IPv6, and ARP are the only routed protocols supported for the interface.
• The interface provides a method of access to the router even if the interfaces or the IOS processes are down.
• The Management Ethernet interface is part of its own VRF. For more information, see the Gigabit Ethernet Management Interface VRF.

The Gigabit Ethernet Management port is always GigabitEthernet0.

In a dual RSP configuration, the Management Ethernet interface on the active RSP will always be Gigabit Ethernet 0, while the Management Ethernet interface on the standby RSP will not be accessible using the Cisco IOS CLI in the same telnet session. The standby RSP can be accessed via console port using telnet.

The port can be accessed in configuration mode like any other port on the chassis.

Router#config t
Enter configuration commands, one per line.  End with CNTL/Z.
Router(config)#interface gigabitethernet0
Router(config-if)#

IP addresses can be configured using ROMmon (IP_ADDRESS= and IP_SUBNET_MASK= commands) and the IOS command-line interface (the ip address command in interface configuration mode).

Assuming the IOS process has not begun running on the chassis, the IP address that was set in ROMmon acts as the IP address of the Management Ethernet interface. In cases where the IOS process is running and has taken control of the Management Ethernet interface, the IP address specified when configuring the Gigabit Ethernet 0 interface in the IOS CLI becomes the IP address of the Management Ethernet interface. The ROMmon-defined IP address is only used as the interface address when the IOS process is inactive.

For this reason, the IP addresses specified in ROMmon and in the IOS CLI can be identical and the Management Ethernet interface will function properly in single RSP configurations.

In dual RSP configurations, however, users should never configure the IP address in the ROMmon on either RP0 or RP1 to match each other or the IP address as defined by the IOS CLI. Configuring matching IP addresses introduces the possibility for an active and standby Management Ethernet interface having the same IP address with different MAC addresses, which will lead to unpredictable traffic treatment or possibility of an RSP boot failure.

The Gigabit Ethernet Management interface is automatically part of its own VRF. This VRF, which is named “Mgmt-intf,” is automatically configured on the chassis and is dedicated to the Management Ethernet interface; no other interfaces can join this VRF. Therefore, this VRF does not participate in the MPLS VPN VRF or any other network-wide VRF.

Placing the management ethernet interface in its own VRF has the following effects on the Management Ethernet interface:

• Many features must be configured or used inside the VRF, so the CLI may be different for certain Management Ethernet functions on the chassis than on Management Ethernet interfaces on other routers.
• Prevents transit traffic from traversing the router. Because all of the interfaces and the Management Ethernet interface are automatically in different VRFs, no transit traffic can enter the Management Ethernet interface and leave an interface, or vice versa.
• Improved security of the interface. Because the Mgmt-intf VRF has its own routing table as a result of being in its own VRF, routes can only be added to the routing table of the Management Ethernet interface if explicitly entered by a user.

The Management Ethernet interface VRF supports both IPv4 and IPv6 address families.

Because users can perform most tasks on a router through the Management Ethernet interface, many tasks can be done by accessing the router through the Management Ethernet interface.

This section documents common configurations on the Management Ethernet interface and includes the following sections: