Understanding Internal Ethernet Interfaces
Internal Ethernet interfaces on the router provide communication between the Routing Engine and the Packet Forwarding Engine. The JUNOS Software 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 (the portion of the router running the JUNOS Software). Information transmitted includes the internal router temperature, the condition of the fans, whether an FPC has been removed or inserted, and information from the craft interface on the LCD panel. The internal Ethernet interface is configured automatically when the JUNOS Software boots.
- J Series, M Series, and MX Series routers and most T Series routers—For J Series, M Series, and MX Series routers, and for T Series routers other than TX Matrix Plus routers or T1600 routers configured in a routing matrix, the JUNOS Software creates the internal Ethernet interface fxp1. The internal Ethernet interface connects the Routing Engine re0 (the portion of the router running the JUNOS Software) to the Packet Forwarding Engine. If the router has redundant Routing Engines, another internal Ethernet interface, fxp2, 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 (RE-TXP-SFC) and Control Board (TXP-CB) function
as a unit, or host subsystem. For each host subsystem in the router,
the JUNOS Software automatically creates two internal Ethernet interfaces, ixgbe0 and ixgbe1, for the two 10-Gigabit Ethernet
ports on the Routing Engine.
The 10-Gigabit Ethernet port at the ixgbe0 interface connects the TX Matrix Plus Routing Engine to the Routing Engines of every T1600 router configured in the routing matrix.
- The port connects the Routing Engine to a 10-Gigabit Ethernet switch on the local Control Board.
- The 10-Gigabit Ethernet switch connects the Control Board to a Gigabit Ethernet switch on the same local Control Board.
- The Gigabit Ethernet switch connects the Control Board to the remote Routing Engines of every T1600 router 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.
- T1600 routers in a routing matrix—On a T1600 router
configured in a routing matrix, the Routing Engine (RE-TXP-LCC) and
Control Board (LCC-CB) function as a unit, or host subsystem. For
each host subsystem in the router, the JUNOS Software automatically
creates two internal Ethernet interfaces, bcm0 and em1, for the two Gigabit Ethernet ports on the Routing Engine.
The Gigabit Ethernet port at the bcm0 interface connects the LCC Routing Engine to the Routing Engines of every other T1600 router configured in the routing matrix.
- The port connects the Routing Engine to a Gigabit Ethernet switch on the local Control Board.
- The switch connects the Control Board to the remote Routing Engines of every other T1600 router configured in the routing matrix.
If a T1600 router 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.
