Brocade Multi-Service IronWare Routing Configuration Guide (Supporting R05.6.00) - Manual (Page 456)

428 Multi-Service IronWare Routing Configuration Guide
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IPv6 Non-Stop Routing support
For example, in a configuration where ftp6.example.com is a server with an IPv6 protocol stack,
when a user pings ftp6.example.com, the device attempts to resolve the AAAA DNS record. In
addition, if the DNS server does not have an IPv6 address, as long as it is able to resolve AAAA
records, it can still respond to DNS queries.
DNS queries of IPv4 and IPv6 DNS servers
IPv4 and IPv6 DNS record queries search through IPv4 and IPv6 DNS servers are described here.
For IPv4 DNS record queries:
• Loop through all configured IPv4 DNS servers.
• If no IPv4 DNS servers are configured, then loop through all configured IPv6 DNS servers (if
any).
For IPv6 DNS record queries:
• Loop through all configured IPv6 DNS servers.
• If no IPv6 DNS servers are configured, then loop through all configured IPv4 DNS servers (if
any).
IPv6 Non-Stop Routing support
When IPv6 Non-Stop-Routing (NSR) is used, peer networking devices do not have knowledge of any
event on the switching over router. All information needed to continue the routing protocol peering
state is transferred to the standby processor so it can pick up immediately upon a switchover. As
NSR does not need the help of neighboring routers during restart, the NSR-capable routers can be
deployed independently in an existing network.
This section describes support for IPv6 Non-Stop-Routing (NSR) on Brocade MLX series and
Brocade NetIron XMR devices. The scope of this section is for IPv6 unicast routing only.
Limitations
• Configuration events that occur closer to switchover may get lost due to CLI synchronization
issues.
• Neighbor, interface, or NSSA translation state changes that occur close to and during the
switchover will not be handled.
• Counters - Traffic counters will not be synchronized. Neighbor and LSA DB counters will be
recalculated on Standby during sync and thus not synchronized.
• OSPF Database Overflow condition for External LSAs - depending on the sequence of
redistribution or new LSAs (from neighbors) the LSAs accepted within the limits of the
database may change upon switchover.
• The NSR hitless failover event may not be completely transparent to the network as after
switchover additional flooding related protocol traffic will be generated to the directly
connected neighbors.
• OSPF Startup Timers - will not be applied upon NSR switchover.