The ORIGIN option on BGP - what is it for?

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1

What makes you mark routes as ORIGIN: IGP vs ORIGIN: EGP?

I just checked out the latest routeviews snapshot to see what the origins
of various routes were set to. The command line
$ bzcat oix-full-snapshot-latest.dat.bz2 | sed -e 's/.* //' | sort \
     > uniq -c | sort -nk1
Gave me a bunch of crap from overly-long lines, and then
   9091 e
682087 ?
7560175 i

Which means that out of 8,251,353 routes in routeviews, only 9,091 are
marked as ORIGIN: EGP, while 682,087 are not configured as one or the
other, and the other *7.5 million* are marked ORIGIN: IGP.

So my question is: What do people use ORIGIN: EGP vs ORIGIN: IGP to
distinguish? What makes a route EGP vs. IGP to you?

  -Peter

2

Not saying this is what others do, but you can certainly use that criteria (via a route-map) to control whether a route is prefered by a peer over two identical (in all other aspects) paths.

DJ

Peter Boothe wrote:

3

Mostly load balancing, thought manually setting it via route maps.

4

Origin is a mandatory transitive attribute which is being used in the
BGP decision algorithm.

If you have a prefix with the same localpref and aspath-length, the
decision will be made based on the lowest origin-value. IGP wins over
EGP, EGP wins over incomplete. You might use it to influence your
inbound traffic.