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Exam 300-410 topic 1 question 434 discussion

Actual exam question from Cisco's 300-410
Question #: 434
Topic #: 1
[All 300-410 Questions]

A customer is running an mGRE DMVPN tunnel over WAN infrastructure between hub and spoke sites. The existing configuration allows NHRP to add spoke routers automatically to the multicast NHRP mappings. The customer is migrating the network from IPv4 to the IPv6 addressing scheme for those spokes' routers that support IPv6 and can run DMVPN tunnel over the IPv6 network.

Which configuration must be applied to support IPv4 and IPv6 DMVPN tunnels on spoke routers?

  • A. tunnel mode ipv6ip 6to4
  • B. tunnel mode ipv6ip auto-tunnel
  • C. tunnel mode ipv6ip 6rd
  • D. tunnel mode ipv6ip isatap
Show Suggested Answer Hide Answer
Suggested Answer: B 🗳️
by ellen_AA at Jan. 17, 2023, 10:42 p.m.

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Sammy3637
3 months, 1 week ago
Selected Answer: B
The main difference between the two is that ISATAP is designed for transporting IPv6 packets within a site, while auto-tunnel can be used between sites.
upvoted 1 times
Sammy3637
2 months, 1 week ago
The tunnel mode ipv6ip isatap is used in the context of IPv6 transition technologies. Specifically, it refers to the ISATAP (Intra-Site Automatic Tunnel Addressing Protocol), which allows IPv6 packets to be transmitted over an IPv4 network.
upvoted 1 times
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bk989
8 months, 1 week ago
it seems 6to4 is best suited for when you need spoke to spoke communication: An automatic 6to4 tunnel may be configured on a border router in an isolated IPv6 network, which creates a tunnel on a per-packet basis to a border router in another IPv6 network over an IPv4 infrastructure. The tunnel destination is determined by the IPv4 address of the border router extracted from the IPv6 address that starts with the prefix 2002::/16, where the format is 2002:border-router-IPv4-address ::/48. Following the embedded IPv4 address are 16 bits that can be used to number networks within the site. The border router at each end of a 6to4 tunnel must support both the IPv4 and IPv6 protocol stacks. 6to4 tunnels are configured between border routers or between a border router and a host.
upvoted 1 times
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tubirubs
8 months, 1 week ago
Selected Answer: A
the goal is to enable both IPv4 and IPv6 traffic to be tunneled over an IPv6 network. The tunnel mode ipv6ip 6to4 configuration is specifically designed to facilitate this by allowing the encapsulation of IPv4 packets within an IPv6 tunnel
upvoted 1 times
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XBfoundX
9 months, 1 week ago
It's B with the command tunnel mode ipv6ip 6to4 basically you incapsulate IPv6 packets into ipv4 packet for traversing an IPv4 network. The question here is the opposite I think they are asking to us that they are migrating in IPv6 and so we need to incapsulate IPv4 packets into IPv6 packets in some cases. So the command that allow us to do so is tunnel mode ipv6ip auto-tunnel, this command allows you to use ipv4 addresses that will be compatible with ipv6
upvoted 4 times
XBfoundX
9 months, 1 week ago
IPv4-compatible This is not a Cisco recommend tunnel type, though it is supported in IOS. As compared to Manual tunnels and GRE tunnels above, IPv4-compatible tunnels are point-to-multipoint where the previous two are simple point-to-point. Automatic IPv4-compatible tunnels use IPv4-compatible IPv6 addresses. IPv4-compatible IPv6 addresses are IPv6 unicast addresses that have zeros in the high-order 96 bits of the address, and an IPv4 address in the low-order 32 bits. They can be written as 0:0:0:0:0:0:A.B.C.D or ::A.B.C.D, where “A.B.C.D” represents the embedded IPv4 address.
upvoted 1 times
XBfoundX
9 months, 1 week ago
About the mode 6to4 ==> "6to4 tunneling" is an IPv6 transition mechanism described in RFC 3056. Like many other transition mechanisms, it enables encapsulation of IPv6 packets into IPv4 for transport across an IPv4 network.
upvoted 2 times
bk989
8 months, 1 week ago
Good catch. I will go with B.
upvoted 1 times
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bk989
8 months, 1 week ago
Isn't Both 6to4 and autotunnel IPv6 tunneled inside IPv4??????
upvoted 1 times
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[Removed]
9 months, 1 week ago
Selected Answer: B
B is correct
upvoted 1 times
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ZamanR
1 year, 4 months ago
B is correct answer
upvoted 1 times
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SAMAKEMM
1 year, 5 months ago
Selected Answer: B
tunnel mode ipv6ip isatap does not support multicast and it is used for intra-sites
upvoted 2 times
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inteldarvid
1 year, 9 months ago
Selected Answer: B
option B: https://netcraftsmen.com/ccie-rs-prep-ipv6-part-2/
upvoted 3 times
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HungarianDish_111
1 year, 10 months ago
Selected Answer: A
Quick overview: IPv6 Automatic IPv4-Compatible Tunnels (and also point-to-multipoint): IPv4-compatible: tunnel mode ipv6ip auto-tunnel -> not recommended either by Cisco nor by IETF/rfc7059 More details: https://netcraftsmen.com/ccie-rs-prep-ipv6-part-2/ https://datatracker.ietf.org/doc/html/rfc7059#section-3.2 https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/interface/configuration/15-s/ir-15-s-book/ip6-auto-comp-tun.pdf 6to4: tunnel mode ipv6ip 6to4 -> for site-to-site/branch-to-branch Limitations: no IGP support, only static route or BGP 6RD: 6RD builds upon the 6to4 tunneling mechanism, and is designed for ISPs (for provider core) -> not for Branch-to-Branch ISATAP: tunnel mode ipv6ip isatap -> designed for intrasite tunneling (within a site/branch), still can be run between sites, too Limitations: -no IPv6 multicast, OSPFv3, EIGRP: neighbors are formed manually with "neighbor" command or need to use static route
upvoted 1 times
HungarianDish_111
1 year, 10 months ago
I doubt that cisco would want the answer "B" with "tunnel mode ipv6ip auto-tunnel". I think that the best fit is "A" "tunnel mode ipv6ip 6to4", however, "D" ISATAP could be an option, too. Question mentions the ability to "add spoke routers automatically to the multicast NHRP mappings" -> I am not sure that it would work with ISATAP. It is hard to decide on the answer without testing dmvpn+6to4 and ISATAP. It think that such a lab is out of scope for ENARSI. All of these are IPv6 over IPv4 tunnel technologies, but the question requests "DMVPN tunnel over the IPv6 network". I wonder if the question is written correctly.
upvoted 1 times
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forccnp
2 years, 1 month ago
Selected Answer: B
tunnel mode ipv6ip auto-tunnel Example: Router(config-if)# tunnel mode ipv6ip auto-tunnel
upvoted 4 times
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Lilienen
2 years, 2 months ago
Selected Answer: D
Based on the document from ellen_AA, I vote for answer D
upvoted 1 times
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ellen_AA
2 years, 3 months ago
Selected Answer: B
Given answer is correct https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/interface/configuration/15-s/ir-15-s-book/ip6-auto-comp-tun.pdf
upvoted 3 times
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C (25%)
B (20%)
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