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Understanding Internal Ethernet Interfaces

Within a router or packet transport switch, internal Ethernet interfaces provide communication between the Routing Engine and the Packet Forwarding Engines. The Junos OS automatically configures internal Ethernet interfaces when the Junos OS boots. The Junos OS boots the packet-forwarding component hardware. When these components are running, the Control Board uses the internal Ethernet interface to transmit hardware status information to the Routing Engine. Information transmitted includes the internal router temperature, the condition of the fans, whether an FPC has been removed or inserted, and information from the LCD on thecraft interface.

To determine the supported internal Ethernet interfaces for your router, see Supported Routing Engines by Chassis.

Note: Do not modify or remove the configuration for the internal Ethernet interface that the Junos OS automatically configures. If you do, the router or packet transport switchwill stop functioning.

• J Series, M Series, and MX Series routers and T Series routers—The Junos OS creates the internal Ethernet interface. The internal Ethernet interface connects the Routing Engine re0 to the Packet Forwarding Engines.

  If the router has redundant Routing Engines, another internal Ethernet interface is created on each Routing Engine (re0 and re1) in order to support fault tolerance, two physical links between re0 and re1 connect the independent control planes. If one of the links fails, both Routing Engines can use the other link for IP communication.

• TX Matrix Plus routers—On a TX Matrix Plus router, the Routing Engine and Control Board function as a unit, or host subsystem. For each host subsystem in the router, the Junos OS automatically creates two internal Ethernet interfaces, ixgbe0 and ixgbe1.

  The ixgbe0 and ixgbe1 interfaces connect the TX Matrix Plus Routing Engine to the Routing Engines of every line-card chassis (LCC) configured in the routing matrix.

  The TX Matrix Plus Routing Engine connects to a high-speed switch through a 10-Gbps link within the host subsystem. The switch provides a 1-Gbps link to each T1600 Routing Engine. The 1-Gbps links are provided through the UTP Category 5 Ethernet cable connections between the TXP-CBs and the LCC-CBs in the LCCs.

  • The TX Matrix Plus Routing Engine connects to a high-speed switch in the local Control Board through a 10-Gbps link within the host subsystem.
  • The Gigabit Ethernet switch connects the Control Board to the remote Routing Engines of every LCC configured in the routing matrix.

  If a TX Matrix Plus router contains redundant host subsystems, the independent control planes are connected by two physical links between the two 10-Gigabit Ethernet ports on their respective Routing Engines.

  • The primary link to the remote Routing Engine is at the ixgbe0 interface; the 10-Gigabit Ethernet switch on the local Control Board also connects the Routing Engine to the 10-Gigabit Ethernet port accessed by the ixgbe1 interface on the remote Routing Engine.
  • The alternate link to the remote Routing Engine is the 10-Gigabit Ethernet port at the ixgbe1 interface. This second port connects the Routing Engine to the 10-Gigabit Ethernet switch on the remote Control Board, which connects to the 10-Gigabit Ethernet port at the ixgbe0 interface on the remote Routing Engine.

  If one of the two links between the host subsystems fails, both Routing Engines can use the other link for IP communication.

• LCC in a routing matrix—On an LCC configured in a routing matrix, the Routing Engine and Control Board function as a unit, or host subsystem. For each host subsystem in the LCC, the Junos OS automatically creates two internal Ethernet interfaces, bcm0 and em1, for the two Gigabit Ethernet ports on the Routing Engine.

  The bcm0 interface connects the Routing Engine in each LCCto the Routing Engines of every other LCC configured in the routing matrix.

  • The Routing Engine connects to a Gigabit Ethernet switch on the local Control Board through a.
  • The switch connects the Control Board to the remote Routing Engines of every other LCC configured in the routing matrix.

  If an LCC in a routing matrix contains redundant host subsystems, the independent control planes are connected by two physical links between the Gigabit Ethernet ports on their respective Routing Engines.

  • The primary link to the remote Routing Engine is at the bcm0 interface; the Gigabit Ethernet switch on the local Control Board also connects the Routing Engine to the Gigabit Ethernet port accessed by the em1 interface on the remote Routing Engine.
  • The alternate link to the remote Routing Engine is at the em1 interface. This second port connects the Routing Engine to the Gigabit Ethernet switch on the remote Control Board, which connects to the Gigabit Ethernet port at the bcm0 interface on the remote Routing Engine.

  If one of the two links between the host subsystems fails, both Routing Engines can use the other link for IP communication.

Each router also has two serial ports, labeled console and auxiliary, for connecting tty type terminals to the router using standard PC-type tty cables. Although these ports are not network interfaces, they do provide access to the router.