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  • 1.  Permanent Interfaces (fxp0,fxp1,fxp2) in M-Series routers

    Posted 07-28-2009 08:09

    Hi All,

     

    I have some doubts regarding permanent interfaces in M-Series routers.

     

    in JNCIA-M/T Studyguide it was mentioned that  ,

     

    fxp0- management ethernet interface - can be configurable by user
    fxp1- internal ethernet interface(connecting RE & PFE) -  configured by JUNOS itself


    in M120(M-onetwenty) series routers, when i gave "show interface terse | match fxp" , its listing only fxp0 anf fxp0.0 interfaces . Neither fxp1 nor fxp1.0 are dispalyed.
    fxp0
    fxp0.0

     

    in M20(M-twenty) series routers, when i gave the same command  "show interface terse | match fxp" , its listing four interfaces

    fxp0
    fxp0.0
    fxp1
    fxp1.0

     

    in M160(M-onesixty) series routers, when i gave the same command ""show interface terse | match fxp", its listing six interfaces
    fxp0
    fxp0.0
    fxp1
    fxp1.0
    fxp2
    fxp2.0


    a) what is the pusrpose of " fxp2 interface " ?

     

     One more observation is both fxp1.0 and fxp2.0 are interfaces are with 10.0.0.4/8 IP address and there is a flag saying that "Is-Default,Is-Primary,Is-Preferred "?

     

    b) Is this IP 10.0.0.4/8 is reserved for fxp1 and fxp2 ?

     

    c) Can't we use this ip address 10.0.0.4/8 on any other transient interfaces ?

     

    Could anyone please explain this or suggest some link ?

     

    Thanks in advance..
    Pradeep


    #fxp0
    #fxp1
    #permanent
    #interfaces
    #fxp2


  • 2.  RE: Permanent Interfaces (fxp0,fxp1,fxp2) in M-Series routers
    Best Answer

    Posted 07-28-2009 08:26

    Have a look at KB2770

     

    On the M120 you have em0 and em1 which server the same function as fxp1 and fxp2

     

    On T Series platforms you have bcm0 similar.

     

    These are all interface for internal RE to PFE communication or RE to other RE communication. The interface IP address are part of the private routing table and can therefor still be used for normal routing. They are not reserved in any way.