link-local address

ePub (114.2 KB) View in various apps on iPhone, iPad, Android, Sony Reader, or Windows Phone The documentation set for this product strives to use bias-free language. For the purposes of this documentation set, bias-free is defined as language that does not imply discrimination based on age, disability, gender, racial identity, ethnic identity, sexual orientation, socioeconomic status, and intersectionality. Exceptions may be present in the documentation due to language that is hardcoded in the user interfaces of the product software, language used based on RFP documentation, or language that is used by a referenced third-party product. Learn more about how Cisco is using Inclusive Language. This document describes how the IPv6 Link-Local address works within a network. The information in this document is based on the Cisco 3700 series router with Cisco IOS® Software Release 12.4 (15)T1. The information in this document was created from the devices in a specific lab environment. All of the devices used in this document started with a cleared (default) configuration. If your network is live, ensure that you understand the potential impact of any command. Refer to Cisco Technical Tips Conventions for more information on document conventions. A Link-Local address is an IPv6 unicast address that can be automatically configured on any interface that uses the Link-Local prefix FE80::/10 (1111 1110 10) and the interface identifier in the modified EUI-64 format. Link-Local addresses are not necessarily bound to the MAC address, although it is common to configure Link-Local addresses using the EUI-64 method (where the MAC address is embedded into the IPv6 address), Link-Local addresses can also be manually configured in the FE80::/10 format with the ipv6 address link-local command. Link-Local addresses in IPv6 are used only on a specific physical link, meaning a local network connection between devices. These addresses are crucial for tasks like automatic address configuration and for the Neighbor Discovery Protocol (NDP), which helps devices on the same link find and communicate with each other. Link-Local addresses allow communication between neighboring nodes without needing a globally unique address. Importantly, IPv6 routers do not forward data with Link-Local addresses beyond the local network. All IPv6-enabled interfaces automatically have a Link-Local unicast address. For this example, the routers R1, R2 and R3 are connected via serial interface and have the IPv6 addresses configured as mentioned in the network diagram. Loopback addresses are configured on the routers R1 and R3, and the routers use OSPFv3 to communicate with each other. This example uses the ping command to demonstrate the connectivity between the routers with Link-Local addresses. The routers R1 and R3 can ping each other with the IPv6 local unicast address, but not with their Link-Local address. However, router R2 is directly connected to R1 and R3 hence it can communicate with both the routers with their Link-Local address, because Link-Local addresses are used only within that local network specific to the physical interface. To verify the OSPF has been configured properly, use the show ipv6 route ospf command in routers R1 and R3. The routers can ping each other with the global unicast address. If the routers use the Link-Local address only, the directly connected networks can communicate. For example, R1 can ping R3 with global unicast address but the two routers cannot communicate with Link-Local addresses. This is shown with the ping and debug ipv6 icmp commands in router R1 and R3. When the router R1 tries to communicate with router R3 with the link local address, the router R1 returns with an ICMP time-out message that indicates the Link-Local address is locally specific and cannot communicate to Link-Local addresses that are outside the directly connected network. For router R2, the routers R1 and R3 are directly connected and can ping th