R21xx-HP FlexFabric 11900 Layer 3 IP Routing Configuration Guide

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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
not belong to the confederation, BGP does not compare it with other routes. As a result, the first route
becomes the optimal route.
To enable MED comparison for routes from confederation peers (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.
ipv4-family [ unicast ] N/A
4. Enable MED comparison for
routes from confederation
peers.
bestroute med-confederation By default, this feature is disabled.
To enable MED comparison for routes from confederation peers (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.
ipv6-family [ unicast ] N/A
4. Enable MED comparison for
routes from confederation
peers.
bestroute med-confederation By default, this feature is disabled.
Configuring the NEXT_HOP attribute
By default, a BGP router does not set itself as the next hop for routes advertised to an IBGP peer or peer
group. In some cases, however, you must configure the advertising router as the next hop to make sure
the BGP peer can find the correct next hop.
For example, as shown in Figure 54,
Router A and Router B establish an EBGP neighbor relationship, and
Router B and Router C establish an IBGP neighbor relationship. If Router C has no route destined for IP
address 1.1.1.1/24, you must configure Router B to set itself 3.1.1.1/24 as the next hop for the network
2.1.1.1 / 24 a d ve r t i s e d t o Ro u t e r C .