FTOS Configuration Guide for the C-Series - Force10 Networks

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 340 MED Route Example
AS 100
Origin
Router B
Router A
OC3 Link
Set MED to 50
T1 Link
Set MED to 100
Router D
Router C
AS 200
Router E
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.
Generally, an IGP indicator means that the route was derived inside the originating AS. EGP generally
means that a route was learned from an external gateway protocol. An INCOMPLETE origin code
generally results from aggregation, redistribution or other indirect ways of installing routes into BGP.
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