Brocade BigIron RX Series Configuration Guide - Manual (Page 1256)

1178 BigIron RX Series Configuration Guide
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ECMP load sharing for IPv6
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In this example, the first IP address in the ip dns server-address... command becomes the primary
gateway address and all others are secondary addresses. Because IP address 201.98.7.15 is the
last address listed, it is also the last address consulted to resolve a query.
Defining an IPv6 DNS entry
IPv6 defines new DNS record types to resolve queries for domain names to IPv6 addresses, as well
as IPv6 addresses to domain names. Brocade devices running IPv6 software support AAAA DNS
records, which are defined in RFC 1886.
AAAA DNS records are analogous to the A DNS records used with IPv4. They store a complete IPv6
address in each record. AAAA records have a type value of 28.
To establish an IPv6 DNS entry for the device, enter the following command.
BigIron RX(config)# ipv6 dns domain-name companynet.com
Syntax: [no] ipv6 dns domain-name <domain name>
To define an IPv6 DNS server address, enter the following command.
BigIron RX(config)# ipv6 dns server-address 200::1
Syntax: [no] ipv6 dns server-address <ipv6-addr> [<ipv6-addr>] [<ipv6-addr>] [<ipv6-addr>]
As an example, in a configuration where ftp6.companynet.com is a server with an IPv6 protocol
stack, when a user pings ftp6.companynet.com, the Brocade 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.
ECMP load sharing for IPv6
The IPv6 route table selects the best route to a given destination from among the routes in the
tables maintained by the configured routing protocols (BGP4, OSPF, static, and so on). The IPv6
route table can contain more than one path to a given destination. When this occurs, the Brocade
device selects the path with the lowest cost for insertion into the routing table. If more than one
path with the lowest cost exists, all of these paths are inserted into the routing table, subject to the
configured maximum number of load sharing paths (by default 4). The device uses Equal-Cost
Multi-Path (ECMP) load sharing to select a path to a destination.
When the device receives traffic for a destination, and the IPv6 route table contains multiple,
equal-cost paths to that destination, the device checks the IPv6 forwarding cache for a forwarding
entry for the destination. The IPv6 forwarding cache provides a fast path for forwarding IPv6 traffic.
The IPv6 forwarding cache contains entries that associate a destination host or network with a
path (next-hop router).
If the IPv6 forwarding cache contains a forwarding entry for the destination, the Brocade device
uses the entry to forward the traffic. If the IPv6 forwarding cache does not contain a forwarding
entry for the destination, the software selects a path from among the available equal-cost paths to
the destination, then creates an entry in the in the cache based on the calculation. Subsequent
traffic for the same destination uses the forwarding entry. Entries remain in the IPv6 forwarding
cache for one minute, then are aged out.
If the path selected by the device becomes unavailable, its entry in the IPv6 forwarding cache is
removed, a new path is selected from the remaining equal-cost paths to the destination, and an
entry is created in the IPv6 forwarding cache using the new path.