IPv6 Addressing Configuration
Router Access and Default Router Selection
Note 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 Automatic Config-
uration of a Global Unicast Address and a Default Router Identity on a VLAN”
on page 4-7.)
■ 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.
Router Redirection
With multiple routers on a VLAN, if the default (first-hop) router for an IPv6-
enabled VLAN on the switch determines that there is a better first-hop router
for reaching a given, remote destination, the default router can redirect the
switch to use that other router as the default router. For further information
on routing IPv6 traffic, refer to the documentation provided for the IPv6
router.
For related information:
■ RFC 2461: “Neighbor Discovery for IP Version 6”
4-28
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