H3C Technologies H3C S12500-X Series Switches - Manual (Page 228)

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Step Command Remarks
4. Enable MED comparison for
routes from different ASs.
compare-different-as-med By default, this feature is disabled.
To enable MED comparison for routes from different ASs (IPv6):
Step Command Remarks
1. Enter system view. system-view N/A
2. Enter BGP view. bgp as-number N/A
3. Enter BGP IPv6 unicast
address family view.
address-family ipv6 [ unicast ] N/A
4. Enable MED comparison for
routes from different ASs.
compare-different-as-med By default, this feature is disabled.
588B
Enabling MED comparison for routes on a per-AS basis
This task enables BGP to compare the MEDs of routes from an AS.
Figure 55 Route selection based on MED (in an IPv4 network)
As shown in
1151H
Figure 55 , Router D learns network 10.0.0.0 from both Router A and Router B. Because
Router B has a smaller router ID, the route learned from Router B is optimal.
Network NextHop MED LocPrf PrefVal Path/Ogn
*>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, it compares the route with the optimal route in
its routing table. Because Router C and Router B reside in different ASs, BGP does not compare the MEDs
of the two routes. Router C has a smaller router ID than Router B so 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
AS 300
AS 100
AS 200
Router A
Router D
Router ID : 3.3.3.3 Router ID : 1.1.1.1
Router C
Eth1/1
1.1.1.1 Eth1/1
3.3.3.3/24
Router B
Router ID : 2.2.2.2
Eth1/1
2.2.2.2/24
AS 400
Router E
10.0.0.0