300-320 · Question #666
Which statement is true about load sharing when you have a single router connecting to a single ISP using multiple links?
The correct answer is A. IGP does the actual load sharing. (A) When a single router connects to a single ISP over multiple physical links, the BGP session is typically established between loopback addresses. The IGP (or static routes) provides the multiple equal-cost paths to reach the peer's loopback, and it is the IGP's ECMP…
Question
Which statement is true about load sharing when you have a single router connecting to a single ISP using multiple links?
Options
- AIGP does the actual load sharing.
- BYou cannot use static routing.
- CIf one link fails, the EBGP session will be lost.
- DYou do not need EBGP multihop configuration.
How the community answered
(54 responses)- A81% (44)
- B11% (6)
- C2% (1)
- D6% (3)
Explanation
(A) When a single router connects to a single ISP over multiple physical links, the BGP session is typically established between loopback addresses. The IGP (or static routes) provides the multiple equal-cost paths to reach the peer's loopback, and it is the IGP's ECMP (equal-cost multipath) that performs the actual load sharing across the physical links. BGP itself only selects one best path; IGP handles the per-packet or per-flow distribution. (B) Static routing can be used in this scenario to provide the multiple next-hops. (C) With loopback-based sessions, losing one link does not drop the BGP session as long as another link remains. (D) EBGP multihop is required when the BGP session is between loopbacks that are not directly connected.
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