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Difficulty: HardIPv6 Static Routing

A network engineer is configuring static routes on a Cisco IOS router to establish connectivity across an enterprise IPv6 infrastructure. Which two statements correctly describe valid IPv6 static route configuration syntax and operational requirements on Cisco IOS?

  1. When specifying a link-local IPv6 address as the next-hop, the local exit interface must also be explicitly specified in the static route command.Answer
  2. A floating static IPv6 route is configured by manually assigning an administrative distance that is higher than the administrative distance of the primary route.Answer
  3. C
    When generating a fully specified IPv6 static route using EUI-64 link-local next-hops, the 64-bit interface identifier is formed solely by inserting FFFE into the middle of the MAC address without modifying any existing bits.
  4. D
    Configuring an IPv6 static route with a global unicast next-hop address strictly requires specifying the local outbound interface alongside the next-hop IPv6 address.

Answer

The two correct statements are: specifying a link-local next-hop address requires defining the local exit interface in the command, and configuring a floating static IPv6 route requires setting an administrative distance higher than that of the primary route.
The statement specifying that a link-local next-hop requires the local exit interface is correct because link-local addresses are non-unique across different interface links. The statement describing floating static routes is correct because setting an administrative distance higher than the active dynamic protocol or primary static route keeps the backup route inactive until the primary route fails.

Step-by-Step Solution

1
Analyze link-local address scoping rules in Cisco IOS static routing.
Link-local addresses (FE80::/10) are link-dependent and non-routable beyond their local segment. Consequently, Cisco IOS requires specifying the egress interface when using a link-local next-hop address.
Without specifying the egress interface, the router cannot determine which local link segment to transmit packets to reach the FE80:: next-hop.
2
Evaluate the administrative distance mechanism for floating static routes.
A floating static route uses a artificially high administrative distance (e.g., AD of 130 backing up OSPF with AD of 110).
The router installs the route into the IPv6 RIB only if lower AD routes for the destination prefix become unavailable.
3
Verify EUI-64 generation rules and global unicast next-hop syntax options.
EUI-64 requires both FFFE insertion and flipping the 7th bit. Global unicast next-hop static routes can be configured recursively without defining an egress interface.
Global unicast addresses are globally unique and can be resolved recursively via the routing table.

Key Concept

IPv6 Static Routing Syntax and Next-Hop Resolution
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Topics

IPv6 Static Routing

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