Editing Border Gateway Protocol (section)

=== Multi-exit discriminators ===

MEDs, defined in the main BGP standard, were originally intended to show to another neighbor AS the advertising AS's preference as to which of several links are preferred for inbound traffic. Another application of MEDs is to advertise the value, typically based on delay, of multiple ASs that have a presence at an [[IXP]], that they impose to send traffic to some destination.

Some routers (like Juniper) will use the Metric from OSPF to set MED.

'''Examples of MED used with BGP when exported to BGP on Juniper SRX'''
<syntaxhighlight lang="console">
# run show ospf route   
Topology default Route Table:
Prefix             Path  Route      NH       Metric NextHop       Nexthop     
                   Type  Type       Type            Interface     Address/LSP
10.32.37.0/24      Inter Discard    IP       16777215
10.32.37.0/26      Intra Network    IP          101 ge-0/0/1.0    10.32.37.241
10.32.37.64/26     Intra Network    IP          102 ge-0/0/1.0    10.32.37.241
10.32.37.128/26    Intra Network    IP          101 ge-0/0/1.0    10.32.37.241

# show route advertising-protocol bgp 10.32.94.169
  Prefix               Nexthop       MED    Lclpref            AS path
* 10.32.37.0/24           Self                 16777215           I
* 10.32.37.0/26           Self                 101                I
* 10.32.37.64/26          Self                 102                I
* 10.32.37.128/26         Self                 101                I
</syntaxhighlight>