CCNA 200-301 v1.1 reference — Network Fundamentals

IPv6 addressing and prefixes

IPv6 address structure and compression rules, /64 prefixes, and how to configure and verify IPv6 addressing on Cisco routers.

Objective 1.8v1.1 exam target

Drop leading zeros inside each group: 0db8 → db8.
Replace the longest run of all-zero groups with :: — allowed once per address.
Never use :: twice: the expansion would be ambiguous.
Mixed case is legal; lowercase is convention (RFC 5952).

Compress and expand

Drop leading zeros → 2001:db8:0:1:0:0:0:a5.
The longest zero run is groups 5–7 (three groups) → 2001:db8:0:1::a5.
To expand 2001:db8::ff: count the present groups (3), fill with zeros to eight → 2001:0db8:0000:0000:0000:0000:0000:00ff.

2001:db8:0:1::a5 is the canonical compressed form.

Configure and verify IPv6 on an interface

Enable IPv6 routing and assign an address — Privileged EXEC → Global + interface configuration

Cisco IOS / IOS XE

configure terminal
ipv6 unicast-routing
interface gigabitethernet0/1
 ipv6 address 2001:db8:100:1::1/64
 no shutdown
 end

Verify

show ipv6 interface brief
show ipv6 interface gi0/1
ping ipv6 2001:db8:100:1::2

Interface lists the global unicast address plus an auto-created link-local FE80:: address.
ipv6 unicast-routing absent leaves the interface up but the router will not forward IPv6.

Without ipv6 unicast-routing, interfaces accept addresses but the device never routes.
The link-local address exists on every IPv6-enabled interface even without a global address.

Changes device configuration.

Element	Value
Total length	128 bits
Notation	8 groups × 4 hex digits, colon-separated
Conventional prefix	/64 (subnet)
Interface ID	Right 64 bits — manual, EUI-64, or random
Loopback	::1
Unspecified	::

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Targets CCNA 200-301 v1.1 objectives. Supplemental blocks are labeled beyond exam scope.