HP 3600 v2 series Configuration Manual page 226

To do...
Configure the default MED value
Enable the comparison of MED of routes from different ASs
Follow these steps to enable the comparison of MED of routes from different ASs:
To do...
Enter system view
Enter BGP view
Enable the comparison of MED of routes
from different ASs
Enable the comparison of MED of routes from each AS
Route learning sequence may affect optimal route selection.
Figure 86 Route selection based on MED
As shown in
Router B has a smaller router ID, the route learned from it is optimal.
Network
*>i 10.0.0.0
* i
When Router D learns network 10.0.0.0 from Router C, it compares the route with the optimal route in its
routing table. Because Router C and Router B reside in different ASs, BGP will not compare the MEDs of
the two routes. Router C has a smaller router ID than Router B, the route from Router C becomes optimal.
Network
*>i 10.0.0.0
* i 10.0.0.0
* i
However, Router C and Router A reside in the same AS, and Router C has a greater MED, so network
10.0.0.0 learned from Router C cannot be optimal.
You can configure the bestroute compare-med command on Router D. After that, Router D puts routes
received from the same AS into a group. Router D then selects the route with the lowest MED from the
same group, and compares routes from different groups. This mechanism avoids the above-mentioned
Figure 86, Router D learns network 10.0.0.0 from both Router A and Router B. Because
NextHop
2.2.2.2
3.3.3.3
NextHop
1.1.1.1
2.2.2.2
3.3.3.3
Use the command...
default med med-value
Use the command...
system-view
bgp as-number
compare-different-as-med
MED LocPrf
50
50
MED LocPrf
60
50
50
214
Remarks
Optional
0 by default
Remarks
—
—
Required
Not enabled by default
PrefVal Path/Ogn
0 300e
0 200e
PrefVal Path/Ogn
0 200e
0 300e
0 200e