Which BGP option is required when load sharing over multiple equal-bandwidth parallel links
from a single CE router to a single ISP router over eBGP? Select the best response.
A.
eBGP Multipath
B.
eBGP Multihop
C.
BGP Synchronization
D.
Public AS numbers
I believe the answer is A
eBGP Multihop:
“To accept and attempt BGP connections to external peers residing on networks that are not directly connected, use the neighbor ebgp-multihop command in router configuration mode. To return to the default, use the no form of this command.”
eBGP Multipath:
“To configure multipath load sharing for external Border Gateway Protocol (eBGP) and internal BGP (iBGP) routes, use the maximum-paths eibgp command in address family configuration mode. To disable multipath load sharing for eBGP and iBGP routes, use the no form of this command.”
http://www.cisco.com/c/en/us/td/docs/ios/iproute_bgp/command/reference/irg_book/irg_bgp3.html
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Question is about “single CE router” so one router with two connections to “single IPS router” so both concretions go to a single IPS router.
To avoid redundancy issues you will have to configure two neighbor commands with two different addresses. That would work, but both neighborships exchange BGP routes and waste bandwidth.
Set loopback addresses on both CE and IPS routers.
Issue neighbor command to this addresses.
Configure “neighbor (neighbor ip) update-source loopback (loopback interface number)” Increase default TTL form 1 to 2, using “neighbor ebgp-multihop 2” command.
and you are good to go!
My answer is B!
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