RE: BGP and Origin Attribute

From: Victor Cappuccio (vcappuccio@desca.com)
Date: Thu Dec 07 2006 - 11:25:45 ART


Why not
By RFC 1771:

a) ORIGIN (Type Code 1):

            ORIGIN is a well-known mandatory attribute that defines the
            origin of the path information. The data octet can assume
            the following values:

                  Value Meaning

                  0 IGP - Network Layer Reachability Information
                               is interior to the originating AS

                  1 EGP - Network Layer Reachability Information
                               learned via EGP

                  2 INCOMPLETE - Network Layer Reachability
                               Information learned by some other means

5.1.1 ORIGIN

*** ORIGIN is a well-known mandatory attribute. ***
 The ORIGIN attribute shall be generated by the autonomous system that
originates the associated routing information. It shall be included in
the UPDATE messages of all BGP speakers that choose to propagate this
information to other BGP speakers.

   All well-known attributes must be passed along (after proper
   updating, if necessary) to other BGP peers

R2#show run | b router bgp 100
router bgp 100
 no synchronization
 bgp log-neighbor-changes
 neighbor 3.3.3.3 remote-as 100
 neighbor 3.3.3.3 update-source Loopback0
 neighbor 3.3.3.3 route-map SETORIGIN in
 no auto-summary
!
ip http server
ip classless
!
!
!
route-map SETORIGIN permit 10
 set origin incomplete
!
!
!
!
!
!
!
line con 0

R2#conf te
Enter configuration commands, one per line. End with CNTL/Z.
R2(config)#router bgp 100
R2(config-router)#no neighbor 3.3.3.3 route-map SETORIGIN in
R2(config-router)#do clear ip bgp * in
R2(config-router)#do show ip bgp
BGP table version is 4, local router ID is 1.1.26.2
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
*>i13.13.13.13/32 3.3.3.3 0 100 0 i
R2(config-router)#neighbor 3.3.3.3 route-map SETORIGIN in
R2(config-router)#do clear ip bgp * in
R2(config-router)#do show ip bgp
BGP table version is 5, local router ID is 1.1.26.2
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
*>i13.13.13.13/32 3.3.3.3 0 100 0 ?
R2(config-router)#

HTH
Victor.-

-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
yousef mohammed
Sent: Wednesday, December 06, 2006 12:37 AM
To: John Jones
Cc: ccielab@groupstudy.com
Subject: Re: BGP and Origin Attribute

You can have ? as as an origin attribute, by setting the attribute using
a
route map command.

On 12/6/06, John Jones <acer0001@gmail.com> wrote:
>
> I know that the origin attribute i is for internal, when the bgp
network
> command or redistribution into BGP. EGP is no longer used. What
> circumstances will you see the ? incomplete attribute? The only time I
can
> think of is when a static route is redistributed into BGP. Are there
any
> other circumstances where the incomplete attribute will show?
>
> Thanks.
>
> John
>
>



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