The configuration of an Alcatel-Lucent 7750 SR is given below. Router R1 has established BGP sessions with routers R2 and R3. Which of the following is TRUE? `` R1>config>router>bgp# info…

Question

R1>config>router>bgp# info
-----------------------------------------------

group "BGP-Peers"
 peer-as 65540
 neighbor 10.10.10.2
 description "R2"
 exit
 neighbor 10.10.10.3
 description "R3"
 peer-as 65550
 exit
exit

Options

• ARouter R1 forms an iBGP session with router R2, and an eBGP session with router R3.
• BRouter R1 forms iBGP sessions with routers R2 and R3.
• CRouter R1 forms eBGP sessions with routers R2 and R3.
• DThe types of BGP sessions with routers R2 and R3 cannot be determined.

• A
  3% (2)
• B
  14% (9)
• C
  6% (4)
• D
  76% (48)

Explanation

Option D is correct because determining iBGP vs. eBGP requires comparing the peer AS to R1's own AS number - but R1's autonomous-system is not shown in the configuration excerpt. Without knowing R1's local AS, it's impossible to tell whether peers AS 65540 (R2) or AS 65550 (R3) are in the same or a different AS.

Options A, B, and C all commit to a definitive session type, but they're making assumptions about R1's AS that the given config simply doesn't support. Note that R2 inherits peer-as 65540 from the group level, while R3 overrides it with peer-as 65550 at the neighbor level - this inheritance hierarchy is a valid and important detail, but it still doesn't resolve the iBGP/eBGP question without R1's own AS.

Memory tip: Think of iBGP/eBGP as a comparison - you need two AS numbers to compare. If the config only gives you the peer's AS, you're always missing half the equation.

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