You have two EBGP peers connected via two parallel serial lines. What should you do to be able to load-balance between two EBGP speakers over the parallel serial lines in both directions
A.
nothing, BGP automatically load-balances the traffic between different autonomous systems on all available links
B.
peer between the eBGP speaker’s loopbacks, configuring eBGP multihop as required, and use an IGP to load-share between the two equal-cost paths between the loopback addresses
C.
configure a loopback as update source for both EBGP peers and have on each AS an IGP to introduce two equal-cost paths to reach the EBGP peer loopback address; it is also necessary to use the next-hop-self command
D.
use the ebgp-load-balance command on the neighbor statement on both sides
E.
configure a loopback as update source for both EBGP peers and have on each AS an IGP to introduce two equal-cost paths to reach the peer loopback address; it is also necessary to use the ebgp-multihop and next-hop-self commands
Explanation:
eBGP Multihop (Load Balancing)RTA#
int loopback 0
ip address 150.10.1.1 255.255.255.0
router bgp 100
neighbor 160.10.1.1 remote-as 200
neighbor 160.10.1.1 ebgp-multihop
neighbor 160.10.1.1 update-source loopback 0
network 150.10.0.0
ip route 160.10.0.0 255.255.0.0 1.1.1.2
ip route 160.10.0.0 255.255.0.0 2.2.2.2
RTB#
int loopback 0
ip address 160.10.1.1 255.255.255.0
router bgp 200
neighbor 150.10.1.1 remote-as 100
neighbor 150.10.1.1 update-source loopback 0
neighbor 150.10.1.1 ebgp-multihop
network 160.10.0.0
ip route 150.10.0.0 255.255.0.0 1.1.1.1
ip route 150.10.0.0 255.255.0.0 2.2.2.1
This example illustrates the use of loopback interfaces, update-source, and ebgp-multihop. The example is
a workaround in order to achieve load balancing between two eBGP speakers over parallel serial lines. In
normal situations, BGP picks one of the lines on which to send packets, and load balancing does not happen.
With the introduction of loopback interfaces, the next hop for eBGP is the loopback interface. You use static
routes, or an IGP, to introduce two equal-cost paths to reach the destination. RTA has two choices to reach
next hop 160.10.1.1: one path via 1.1.1.2 and the other path via 2.2.2.2. RTB has the same choices.