Ip unnumbered loopback0

Discussion in 'Cisco' started by AM, Sep 12, 2005.

  1. AM

    AM Guest

    As only sometime there are devices connected to Ethernet0 of my router, that interface is often down. I have a VPN built
    using LAN behind router but I can not use any service available on the router using that interface. So I can not
    connect through the tunnel to the router or use SNMP over the tunnel.

    I specified loopback0 with the address of the Etrhernet and I gave the command "ip unnumbered loopback0" to the ethernet.
    This was the response

    Point-to-point (non-multi-access) interfaces only

    and I can not see the above statement in the ethernet 0 section.

    Is it correct? Will NAT process work correctly for workstation behind the router?

    Thanks,

    Alex.
    AM, Sep 12, 2005
    #1
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  2. AM

    Cen Guest

    ip unnumbered command can only be used for point to point link (e.g.
    serial)
    Ethernet is NOT one of them, as it is a multiaccess media therefore it
    cannot borrow the address from loopback


    "AM" <> wrote in message
    news:BcjVe.219$...
    > As only sometime there are devices connected to Ethernet0 of my router,
    > that interface is often down. I have a VPN built using LAN behind router
    > but I can not use any service available on the router using that
    > interface. So I can not connect through the tunnel to the router or use
    > SNMP over the tunnel.
    >
    > I specified loopback0 with the address of the Etrhernet and I gave the
    > command "ip unnumbered loopback0" to the ethernet.
    > This was the response
    >
    > Point-to-point (non-multi-access) interfaces only
    >
    > and I can not see the above statement in the ethernet 0 section.
    >
    > Is it correct? Will NAT process work correctly for workstation behind the
    > router?
    >
    > Thanks,
    >
    > Alex.
    Cen, Sep 12, 2005
    #2
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  3. AM

    AM Guest

    Cen wrote:
    > ip unnumbered command can only be used for point to point link (e.g.
    > serial)
    > Ethernet is NOT one of them, as it is a multiaccess media therefore it
    > cannot borrow the address from loopback
    >


    So how to have ethernet0's address available even if Ethernet0 is down? Or there are no possibilities to do that?

    Alex.
    AM, Sep 13, 2005
    #3
  4. AM

    Nick Ersdown Guest

    You could try using 'no keepalive' under the E0 interface. The interface
    will always stay up even if the cable is disconnected.

    Regards,

    Nick Ersdown
    Your real-time, not too serious, view of the latest global IT security
    issues.
    www.ar53.com


    "AM" <> wrote in message
    news:DivVe.969$...
    > Cen wrote:
    >> ip unnumbered command can only be used for point to point link (e.g.
    >> serial)
    >> Ethernet is NOT one of them, as it is a multiaccess media therefore it
    >> cannot borrow the address from loopback
    >>

    >
    > So how to have ethernet0's address available even if Ethernet0 is down? Or
    > there are no possibilities to do that?
    >
    > Alex.
    Nick Ersdown, Sep 13, 2005
    #4
  5. Except then any other devices on the Ethernet will be unable to
    reach the router using the E0 IP address because for them it is
    still local. Ditto for any devices which reach that Ethernet to
    get to the router via any other routers on that Ethernet.

    A far better solution for network management is to configure the
    services which must remain up to use the Loopback IP address so that
    it can be reached as long as any path remains to the router. For
    local devices which are too dumb to use a default gateway to get
    to the service, proxy ARP is your friend.

    Good luck and have fun!
    --
    Vincent C Jones, Consultant Expert advice and a helping hand
    Networking Unlimited, Inc. for those who want to manage and
    Tenafly, NJ Phone: 201 568-7810 control their networking destiny
    http://www.networkingunlimited.com

    In article <dg61jb$1ac$1$>,
    Nick Ersdown <> wrote:
    >You could try using 'no keepalive' under the E0 interface. The interface
    >will always stay up even if the cable is disconnected.
    >
    >Regards,
    >
    >Nick Ersdown
    >
    >"AM" <> wrote in message
    >news:DivVe.969$...
    >> Cen wrote:
    >>> ip unnumbered command can only be used for point to point link (e.g.
    >>> serial)
    >>> Ethernet is NOT one of them, as it is a multiaccess media therefore it
    >>> cannot borrow the address from loopback
    >>>

    >>
    >> So how to have ethernet0's address available even if Ethernet0 is down? Or
    >> there are no possibilities to do that?
    >>
    >> Alex.
    Vincent C Jones, Sep 13, 2005
    #5
  6. AM

    AM Guest

    Vincent C Jones wrote:
    > Except then any other devices on the Ethernet will be unable to
    > reach the router using the E0 IP address because for them it is
    > still local. Ditto for any devices which reach that Ethernet to
    > get to the router via any other routers on that Ethernet.


    I must add one more subnet for each VPN tunnel I built :(

    Alex.
    AM, Sep 13, 2005
    #6
  7. AM

    AM Guest

    Nick Ersdown wrote:

    > You could try using 'no keepalive' under the E0 interface. The interface
    > will always stay up even if the cable is disconnected.


    This tip doesn't work

    Alex.
    AM, Sep 13, 2005
    #7
  8. In article <iADVe.2088$>, AM <> wrote:
    :Vincent C Jones wrote:
    :> Except then any other devices on the Ethernet will be unable to
    :> reach the router using the E0 IP address because for them it is
    :> still local. Ditto for any devices which reach that Ethernet to
    :> get to the router via any other routers on that Ethernet.

    :I must add one more subnet for each VPN tunnel I built :(

    By "tunnel" do you mean "peer" or "security association" ?

    All the security associations going to a given peer could be routed
    through a common IP address, the route to which being was what was
    varying.
    --
    Ceci, ce n'est pas une idée.
    Walter Roberson, Sep 13, 2005
    #8
  9. AM

    AM Guest

    Walter Roberson wrote:

    > In article <iADVe.2088$>, AM <> wrote:
    > :Vincent C Jones wrote:
    > :> Except then any other devices on the Ethernet will be unable to
    > :> reach the router using the E0 IP address because for them it is
    > :> still local. Ditto for any devices which reach that Ethernet to
    > :> get to the router via any other routers on that Ethernet.
    >
    > :I must add one more subnet for each VPN tunnel I built :(
    >
    > By "tunnel" do you mean "peer" or "security association" ?


    IPsec SA, that where I specify which traffic coming from and going to must be encrypted. I must add also traffic coming
    from my LAN to the loopback interface. And I have 30... humpf... Just to standardize all connections, otherwise I need
    only one chabge.

    Alex.
    AM, Sep 13, 2005
    #9
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