IPv6 Configuration Guide K/KA/KB.15.15

PageDefaultAdvertisement Value
187200 secondsminimum
18864current hop limit
1881800 seconds (3 x max. transmission interval)default lifetime
188Unspecified (0)reachable time
189Unspecified (0)retransmission timer
1
Default operation excludes prefixes of stateless autoconfigured addresses.
RA basics
• Enabling IPv6 unicast routing on a routing switch initiates transmission of RAs on active,
IPv6-enabled VLANs unless RA transmission has been suppressed.
• RAs are not routed.
• A host response to an RA depends on how the host implements IPv6. Generally, settings in
an RA received by a host replaces settings received from an earlier RA. Settings configured
directly on a host by an operator may override values received in an RA for the same settings.
• When a host receives a default "unspecified" value in an RA, the host applies either its own
current setting for that value, or the defaults specified in RFC 4861 or other applicable RFCs,
depending on how IPv6 is implemented in the host.
• The M-bit and O-bit flags enable RAs to be configured either to act as the sole source of host
addressing and related settings, or to direct the host to use a DHCPv6 server for some or all
such settings.
About setting up your IPv6 RA policy
• Is there a role for a DHCPv6 server in host configuration on a given VLAN, and what host
services and policy will be configured?
Affects M-bit and O-bit options.
• What is the ND policy that should be advertised?
Includes hop-limit for host-generated traffic, the default router period, neighbor reachable time,
and retransmit time for neighbor solicitations.
• What prefixes should be advertised, and what prefixes should be suppressed?
Prefixes configured on the routing switch VLAN interface will be included in RAs on that VLAN
unless specifically denied.
• What should be the maximum and minimum intervals (in seconds) for transmitting RAs?
• Are there any VLANs or tunnels on the routing switch where RAs should be suppressed?
• Will multiple routing devices be used to send RAs on a VLAN?
The first RA received by a host determines the default router for that host. Other routers
included in subsequent RAs received by the host become backup default routers for that
host.
•
• What, if any, differences are acceptable in RAs from different routing devices?
Steps for configuring IPv6 RAs
When IPv6 unicast routing is enabled on the routing switch, RAs are transmitted on all IPv6-enabled
VLANs or tunnels unless explicitly suppressed globally or per-VLAN.
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