R3721-F3210-F3171-HP High-End Firewalls Network Management Configuration Guide-6PW101

441
*>i 10.0.0.0 2.2.2.2 50 0 300e
* i 3.3.3.3 50 0 200e
When Router D learns network 10.0.0.0 from Router C which has a smaller router ID than Router
B, the route from Router C becomes optimal.
Network NextHop MED LocPrf PrefVal Path/Ogn
*>i 10.0.0.0 1.1.1.1 60 0 200e
* i 10.0.0.0 2.2.2.2 50 0 300e
* i 3.3.3.3 50 0 200e
However, Router C and Router B reside in the same AS, and BGP will compare the MEDs of them.
Since Router C has a greater MED, network 10.0.0.0 learned from it is not optimal.
You can configure the bestroute compare-med command on Router D. After that, Router D will put
routes received from the same AS into a group. For the same group, the route with the lowest MED
is selected. Then, it compares routes from different groups. This mechanism avoids the
above-mentioned problem. The following output is the BGP routing table on Router D after the
comparison of MED of routes from each AS is enabled. Network 10.0.0.0 learned from Router C
is the optimal route.
Network NextHop MED LocPrf PrefVal Path/Ogn
*>i 10.0.0.0 3.3.3.3 50 0 200e
* i 10.0.0.0 2.2.2.2 50 0 300e
* i 1.1.1.1 60 0 200e
BGP load balancing cannot be implemented because load balanced routes must have the same
AS-path attribute.
To enable the comparison of MED of routes from each AS:
Ste
p
Command Remarks
1. Enter system view.
system-view N/A
2. Enter BGP view. bgp as-number N/A
3. Enable the comparison of MED
of routes from each AS
bestroute compare-med
Optional.
Not enabled by default.
4. Enable the comparison of MED of routes from confederation peers
To enable the comparison of MED of routes from confederation peers:
Ste
p
Command Remarks
1. Enter system view.
system-view N/A
2. Enter BGP view. bgp as-number N/A
3. Enable the comparison of MED
of routes from confederation
peers.
bestroute med-confederation
Optional.
Not enabled by default.
NOTE:
The MED attributes of routes from confederation peers are not compared if their AS-path attributes contain
A
S numbers that do not belong to the confederation, such as these three routes: AS-path attributes of them
are 65006 65009, 65007 65009 and 65008 65009, and MED values of them are 2, 3, and 1. Because
the third route contains an AS number that does not belon
g
to the confederation, the first route becomes
the optimal route.