When only central CEF (not distributed CEF) is enabled on 7500-series router...

Discussion in 'Cisco' started by ETLALAR, Jan 16, 2004.

  1. ETLALAR

    ETLALAR Guest

    ....does the whole packet cross the router bus? Or maybe just a part of
    packet containing essential info (IP header, TCP/UDP headers, etc) is
    actually sent to RSP (similar to Juniper Networks routers' J-cell)?

    I've read "CEF overview" and other docs from Cisco website but apart from
    one diagram on page 8 (see
    http://www.cisco.com/warp/public/732/Tech/switching/docs/cef_ov_final.pdf )
    there is nothing specific.

    Thanks & regards

    Alex
     
    ETLALAR, Jan 16, 2004
    #1
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  2. ETLALAR

    AnyBody43 Guest

    "ETLALAR" <> wrote in message news:<bu9bhg$f1a$>...
    > ...does the whole packet cross the router bus? Or maybe just a part of
    > packet containing essential info (IP header, TCP/UDP headers, etc) is
    > actually sent to RSP (similar to Juniper Networks routers' J-cell)?
    >
    > I've read "CEF overview" and other docs from Cisco website but apart from
    > one diagram on page 8 (see
    > http://www.cisco.com/warp/public/732/Tech/switching/docs/cef_ov_final.pdf )
    > there is nothing specific.
    >
    > Thanks & regards
    >
    > Alex


    Hi,

    I am not current on this and it is all from rather a while ago,
    however with say 12.0 (11.1CC too) I seem to recall that
    the whole packet was copied to the RSP and then was
    copied back to the appropriate line card thereby hitting
    the bus twice in all cases when not doing distributed
    forwarding. For example even when the output port
    was on the same linecard as the input port.

    I will have a read of the paper and see if it
    stimulates the grey matter further.

    If you are worrying about this then the obvious answer if to
    move to more modern hardware which moves along pretty nicely
    and disposes of a lot of these concerns.
     
    AnyBody43, Jan 18, 2004
    #2
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  3. On Fri, 16 Jan 2004 18:47:39 -0000, ETLALAR wrote:
    > ...does the whole packet cross the router bus?


    The entire packet is send to the RSP, a routing decision is made, and
    it's send out the appropiate interface, if you enabled distributed CEF,
    the routing decision is made on the ingress VIP, and the send to the
    output interface, which is on the same VIP never hit the bus.

    > Or maybe just a part of packet containing essential info (IP header,
    > TCP/UDP headers, etc) is actually sent to RSP (similar to Juniper
    > Networks routers' J-cell)?


    The architecture of the Cisco 7500 series router and that of a Juniper M
    series are not compareable.

    > I've read "CEF overview" and other docs from Cisco website but apart from
    > one diagram on page 8 (see
    > http://www.cisco.com/warp/public/732/Tech/switching/docs/cef_ov_final.pdf )
    > there is nothing specific.


    --
    Jesper Skriver, CCIE #5456, FreeBSD committer
     
    Jesper Skriver, Jan 19, 2004
    #3
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