Cisco CCNA (200-301)Network FundamentalsMedium
A network administrator is troubleshooting an IPv6-enabled client that cannot reach resources outside its local subnet. The client has an IPv6 address, but a packet capture shows no default gateway being advertised or configured. Which IPv6 address type is typically used by routers to advertise themselves as default gateways on a local segment?
- AGlobal Unicast Address (GUA)
- BMulticast Address (FF02::1)
- CLink-Local Address (LLA)
- DUnique Local Address (ULA)
Show answer & explanationAnswer & explanation
Correct answer: C. Link-Local Address (LLA)
Routers use their Link-Local Address (LLA) as the source address for Router Advertisements (RAs) and typically advertise their LLA as the default gateway for hosts on the local link. This allows hosts to communicate with the router on the local segment even without a GUA.
Why the other options are wrong
- A. GUAs are globally routable, but the router advertises its LLA as the default gateway address on the local link.
- B. FF02::1 is the all-nodes multicast address, used for general communication to all IPv6 nodes on the link, not a specific default gateway address.
- D. ULAs are for private IPv6 networks, similar to RFC 1918 IPv4, not typically used as default gateways.
IPv6 Link-Local Address (LLA)
An IPv6 address automatically configured on every IPv6-enabled interface, starting with 'fe80::', used for communication only on the local link.
- Always starts with fe80::/10 prefix.
- Non-routable beyond the local link.
- Used for Neighbor Discovery Protocol (NDP), including Router Advertisements (RAs) and as the default gateway for hosts.
Memory trick: Global is for World, Link-Local for Lane, Unique-Local for Home, Multicast for Many.