HP 6125G HP 6125G & 6125G/XG Blade Switches Layer 3 - IP Routing Confi - Page 154

Enabling the comparison of MED of routes from confederation peers The MED attributes of routes from confederation peers are not compared if their AS_PATH attributes contain AS 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 belong to the confederation, the first route becomes the optimal route. To enable the comparison of MED of routes from confederation peers: Step 1. Enter system view. 2. Enter BGP view. 3. Enable the comparison of MED of routes from confederation peers. Command system-view bgp as-number bestroute med-confederation Remarks N/A N/A Optional. Not enabled by default. Configuring the NEXT_HOP attribute By default, when advertising routes to an IBGP peer or peer group, a BGP router does not set itself as the next hop. However, to ensure a BGP peer can find the correct next hop in some cases, you must configure the router as the next hop for routes sent to the peer. For example, as shown in Figure 59, Router A and Router B establish an EBGP neighbor relationship, and Router B and Router C establish an IBGP neighbor relationship. When Router B advertises a network learned from Router A to Router C, if Router C has no route to IP address 1.1.1.1/24, you must configure Router B to set itself as the next hop (3.1.1.1/24) for the route to be sent to Router C. Figure 59 NEXT_HOP attribute configuration 1 If a BGP router has two peers on a common broadcast network, it does not set itself as the next hop for routes sent to an EBGP peer by default. As shown in Figure 60, Router A and Router B establish an EBGP neighbor relationship, and Router B and Router C establish an IBGP neighbor relationship. They are on the same broadcast network 1.1.1.0/24. When Router B sends EBGP routes to Router A, it does not set itself as the next hop by default. However, you can configure Router B to set it as the next hop (1.1.1.2/24) for routes sent to Router A by using the peer next-hop-local command as needed. Figure 60 NEXT_HOP attribute configuration 2 144