• When advertising a self-originated route to an eBGP peer, a BGP speaker sets the NEXT_HOP for the route to
the address of its sending interface.
• When sending a received route to an eBGP peer, a BGP speaker sets the NEXT_HOP for the route to the
address of the sending interface.
• When sending a route received from an eBGP peer to an iBGP peer, a BGP speaker does not modify the
NEXT_HOP attribute. If load-balancing is configured, the NEXT_HOP attribute will be modified. For load-
balancing information, refer to BGP route selection.
Figure 59: NEXT_HOP attribute
MED (MULTI_EXIT_DISC)
The MED attribute is exchanged between two neighboring ASs, each of which does not advertise the attribute to
any other AS. Similar to metrics used by IGP, MED is used to determine the best route for traffic going into an AS.
When a BGP router obtains multiple routes to the same destination but with different next hops, it considers the
route with the smallest MED value the best route if other conditions are the same. As shown below, traffic from
AS10 to AS20 travels through Router B that is selected according to MED.
Figure 60: MED attribute
In general, BGP compares MEDs of routes received from the same AS only.
NOTE:
The current implementation supports using the always-compare-med command to force BGP
to compare MED values of routes received from different ASs.
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Aruba 3810 / 5400R Multicast and Routing Guide for ArubaOS-
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