Click the exhibit. Assume all router-IDs are properly configured. Which of the following configurations is required on the Alcatel-Lucent 7750 SR router A to establish an IPv6 BGP session to router D?

Question

Options

• Agroup "IPv6_eBGP" family ipv6 type external peer-as 65550 neighbor 2001:DB8:3::3 exit
• Bgroup "IPv6_eBGP" type external peer-as 65550 neighbor 2001:DB8:3::3 exit
• Cgroup "IPv6_eBGP" family ipv6 peer-as 65550 neighbor 2001:DB8:13::31 exit
• Dgroup "IPv6_eBGP" type external peer-as 65550 neighbor 2001:DB8:13::31 exit

• A
  4% (1)
• B
  12% (3)
• C
  80% (20)
• D
  4% (1)

Explanation

Option C is correct because it includes the mandatory family ipv6 directive (required to activate the IPv6 address family in the BGP group) and uses the correct neighbor address 2001:DB8:13::31, which is Router D's IPv6 address on the shared link with Router A. On Nokia SROS, type external is not required - when peer-as specifies an AS number different from the local AS, the router automatically treats the session as eBGP, making type external redundant.

• A is wrong: Uses the incorrect neighbor address 2001:DB8:3::3 (a different subnet, not the A-to-D link), so the session would target the wrong peer.
• B is wrong: Missing family ipv6 (so IPv6 NLRI won't be negotiated) and uses the wrong neighbor address - two errors.
• D is wrong: Missing family ipv6, meaning the BGP group defaults to IPv4 unicast only, so no IPv6 prefixes will be exchanged even if the session comes up.

Memory tip: On Nokia 7750 SR, think "family first, type optional" - family ipv6 is mandatory to enable IPv6 BGP, but type external is implied whenever peer-as differs from your local AS, so you only need it for clarity, not correctness. Always verify the neighbor IP belongs to the directly connected link in the exhibit.

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