Router Solicitations; Default Ipv6 Router - HP 2520-8 Configuration Manual

IPv6 Addressing Configuration
Router Access and Default Router Selection
N o t e
1-24

Router Solicitations

When an IPv6 interface becomes operational on the switch, a router solicita-
tion is automatically sent to trigger a router advertisement (RA) from any IPv6
routers reachable on the VLAN. (Router solicitations are sent to the All-
Routers multicast address; ff02::2. Refer to "Router Access and Default Router
Selection" on page 1-23.) If an RA is not received within one second of sending
the initial router solicitation, the switch sends up to three additional solicita-
tions at intervals of four seconds. If an RA is received, the sending router is
added to the switch's default router list and the switch stops sending router
solicitations. If an RA is not received, then IPv6 traffic on that VLAN cannot
be routed, and the only usable unicast IPv6 address on the VLAN is the link-
local address.
If the switch does not receive a router advertisement after sending the router
solicitations, as described above, then no further router solicitations are sent
on that VLAN unless a new IPv6 setting is configured, IPv6 on the VLAN is
disabled, then re-enabled, or the VLAN itself is disconnected, then recon-
nected.

Default IPv6 Router

If IPv6 is enabled on a VLAN where there is at least one accessible IPv6 router,
the switch selects a default IPv6 router. (Refer to "Enabling Autoconfiguration
of a Global Unicast Address and a Default Router Identity on a VLAN" on
page 1-4.)
■ If the switch receives router advertisements (RAs) from a single IPv6
router on the same VLAN or subnet, the switch configures a global unicast
address and selects the advertising router as the default IPv6 router.
If multiple IPv6 routers on a VLAN send RAs advertising the same
■
network, the switch configures one global unicast address and selects one
router as the default router, based on the router's relative reachability,
using factors such as router priority and route cost.
■ If multiple IPv6 routers on a VLAN send RAs advertising different subnets,
the switch configures a corresponding global unicast address for each RA
and selects one of the routers as the default IPv6 router, based on route
cost. When multiple RAs are received on a VLAN, the switch uses the
router priority and route cost information included in the RAs to identify
the default router for the VLAN.