300-410 ENARSI: Implementing Cisco Enterprise Advanced Routing and ServicesDemo

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QuestionQ576

Infrastructure Security

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Refer to the exhibit. PC-2 failed to establish a Telnet connection to the terminal server.

Which configuration resolves the issue?

  • A Gateway-Router(config)#ipv6 access-list Default_Access Gateway-Router(config-ipv6-acl)#sequence 25 permit tcp host 2018:DB1:A:B::2 host 2018:DB1:A:C::1 eq telnet
  • B Gateway-Router(config)#ipv6 access-list Default_Access Gateway-Router(config-ipv6-acl)#no sequence 20 Gateway-Router(config-ipv6-acl)#sequence 5 permit tcp host 2018:DB1:A:B::2 host 2018:DB1:A:C::1 eq telnet
  • C Gateway-Router(config)#ipv6 access-list Default_Access Gateway-Router(config-ipv6-acl)#permit tcp host 2018:DB1:A:B::2 host 2018:DB1:A:C::1 eq telnet
  • D Gateway-Router(config)#ipv6 access-list Default_Access Gateway-Router(config-ipv6-acl)#sequence 15 permit tcp host 2018:DB1:A:B::2 host 2018:DB1:A:C::1 eq telnet
Explanation

IPv6 ACL entries are processed in sequence order, and the first matching entry determines the result. Telnet traffic from 2018:DB1:A:B::2 to 2018:DB1:A:C::1 currently matches sequence 20 (deny tcp any host 2018:DB1:A:C::1 eq telnet) before sequence 30 can permit it. Adding the PC-2 Telnet permit at sequence 15 places it before the deny while preserving the deny for other sources.

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