H3C Technologies H3C S12500-X Series Switches - Manual (Page 229)

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* i 3.3.3.3 50 0 200e
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 should not be optimal.
You can configure the bestroute compare-med command to enable MED comparison for routes from the
same AS on Router D. After that, Router D puts the routes received from each AS into a group, selects the
route with the lowest MED from each group, and compares routes from different groups. This mechanism
avoids the above-mentioned problem. The following output shows the BGP routing table on Router D after
this feature is enabled. Network 10.0.0.0 learned from Router B is the optimal route.
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
* i 1.1.1.1 60 0 200e
To enable MED comparison for routes on a per-AS basis (IPv4):
Step Command Remarks
1. Enter system view. system-view N/A
2. Enter BGP view or BGP-VPN
instance view.
• Enter BGP view:
bgp as-number
• Enter BGP-VPN instance view:
a. bgp as-number
b. ip vpn-instance
vpn-instance-name
N/A
3. Enter BGP IPv4 unicast
address family view or
BGP-VPN IPv4 unicast
address family view.
address-family ipv4 [ unicast ] N/A
4. Enable MED comparison for
routes on a per-AS basis.
bestroute compare-med By default, this feature is disabled.
To enable MED comparison for routes on a per-AS basis (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 on a per-AS basis.
bestroute compare-med By default, this feature is disabled.
589B
Enabling MED comparison for routes from confederation peers
This task enables BGP to compare the MEDs of routes received from confederation peers. However, if a
route received from a confederation peer has an AS number that does not belong to the confederation,
BGP does not compare the route with other routes. For example, a confederation has three AS numbers
65006, 65007, and 65009. BGP receives three routes from different confederation peers. The AS_PATH
attributes of these routes are 65006 65009, 65007 65009, and 65008 65009, and the MED values of
them are 2, 3, and 1. Because the third route's AS_PATH attribute contains AS number 65008 that does