Origin - Dell Force10 C150 Configuration Manual

One AS assigns the MED a value and the other AS uses that value to decide the preferred path. For this
example, assume the MED is the only attribute applied. In
places. Each connection is a BGP session. AS200 sets the MED for its T1 exit point to 100 and the MED
for its OC3 exit point to 50. This sets up a path preference through the OC3 link. The MEDs are advertised
to AS100 routers so they know which is the preferred path.
An MED is a non-transitive attribute. If AS100 sends an MED to AS200, AS200 does not pass it on to
AS300 or AS400. The MED is a locally relevant attribute to the two participating Autonomous Systems
(AS100 and AS200).
Note that the MEDs are advertised across both links, so that if a link goes down AS 1 still has connectivity
to AS300 and AS400.
Figure 10-6. MED Route Example
Router A
AS 100
Router B
Set MED to 50
Note: With FTOS Release 8.3.1.0, configuring the
advertises the IGP cost as MED to outbound EBGP peers when redistributing routes. The configured
value overwrites the default IGP cost.
metric

Origin

The Origin indicates the origin of the prefix, or how the prefix came into BGP. There are three Origin
codes: IGP, EGP, INCOMPLETE.
• IGP indicated the prefix originated from information learned through an interior gateway protocol.
• EGP indicated the prefix originated from information learned from an EGP protocol, which NGP
replaced.
• INCOMPLETE indicates that the prefix originated from an unknown source.
Set MED to 100
T1 Link
Router C
OC3 Link
Router D
set metric-type internal
Figure 10-6, AS100 and AS200 connect in two
AS 200
Router E
command in a route-map
Border Gateway Protocol IPv4 (BGPv4) | 215
set