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3928 Views 6 Replies Latest reply: Apr 4, 2012 5:29 PM by riedmueller RSS

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show ip bgp "i" in AS path? but its eBGP...

Aug 21, 2011 3:36 AM

Stephen 488 posts since
Apr 22, 2011

Hey guys,

 

Just reading the Wendell Odom 642-902 book and come accross the following table:

eBGPwtf.jpg

 

He states that all routes learned in the table are eBGP routes because there is no i in the 3rd column.  Not too sure what he means by this, however, my question is; if all these routes are eBGP, then what does the "i" mean in the Path column (on the far right hand side)?

 

Regards,

Stephen

  • Brian 2,971 posts since
    Aug 17, 2009
    Currently Being Moderated
    1. Aug 21, 2011 4:23 AM (in response to Stephen)
    Re: show ip bgp "i" in AS path? but its eBGP...

    The "i" in the path column as in the below example:

     

    I3_1#sh ip bgp

    BGP table version is 4, local router ID is 3.3.3.3

    Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,

                  r RIB-failure, S Stale

    Origin codes: i - IGP, e - EGP, ? - incomplete

     

       Network          Next Hop            Metric LocPrf Weight Path

    *> 128.107.0.0      192.168.1.5              0             0 11 i

    *> 172.20.0.0       0.0.0.0                  0         32768 i

    *> 172.30.0.0       0.0.0.0                  0         32768 i

    I3_1#

     

    relates to the "Origin codes" above in RED.  Key thing to note, i = IGP does not stand for Internal Gateway Protocol nor does e = EGP stand for External BGP.  The "e = EGP" stand for the old EGP protocol which has not been used since 12.3 or there abouts and you should not see this in use today.  The "i = IGP" stands for routes injected via the "network", "aggregate-address" or "neighbor-default-originte" commands.

     

    Brian

  • cadetalain 2,642 posts since
    Sep 18, 2008
    Currently Being Moderated
    2. Aug 21, 2011 10:48 AM (in response to Stephen)
    Re: show ip bgp "i" in AS path? but its eBGP...

    Hi,

     

    If ther is no i just after the >  or * sign then this is not an iBGP learned route so it is a locally generated route in which case next-hop is 0.0.0.0 or an eBGP route.

    The last I as explained above is for the origin of the route that is how was he first put into the BGP table, it could be i or e or ? where e stands for egp which is predecessor to BGP and ? stands for unknown so was redistributed and i is via a network command or aggregate or the last one cited by Brian( I would have forgot this one).

     

    Regards.

     

    Alain.

  • taz 95 posts since
    Jul 6, 2010
    Currently Being Moderated
    3. Apr 4, 2012 3:34 PM (in response to Brian)
    Re: show ip bgp "i" in AS path? but its eBGP...

    Hi. I'm stuggling with the difference too. I understand the 'i" at the end means its from "network" or "aggreagate" - i imagine for the AS whose number is to the left of it. This would be the origin in path selection ?? (weight/local pref/route originate/aspath/origin)

     

    So what is the "i" in the 3rd column meaning? Would that mean it originated on the router being looked at as opposed to another router? I think I need an example to clarify

    many thanks

  • riedmueller 26 posts since
    Jun 24, 2009
    Currently Being Moderated
    4. Apr 4, 2012 5:00 PM (in response to taz)
    Re: show ip bgp "i" in AS path? but its eBGP...

    Try this (stolen from a powerpoint)

    show ip bgp output.jpg

  • taz 95 posts since
    Jul 6, 2010
    Currently Being Moderated
    5. Apr 4, 2012 5:12 PM (in response to riedmueller)
    Re: show ip bgp "i" in AS path? but its eBGP...

    THANK YOU!!!!!!!!

     

    That powerpoint slide is so sweet

  • riedmueller 26 posts since
    Jun 24, 2009
    Currently Being Moderated
    6. Apr 4, 2012 5:29 PM (in response to taz)
    Re: show ip bgp "i" in AS path? but its eBGP...

    I agree. I wish I could remember where I found it so I could credit the author...

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