Cisco 3750G Configuration Guide - Page 918

SDM Templates, ipv6 address, eui-64, sdm prefer

Page 918 highlights

Understanding IPv6 Chapter 36 Configuring IPv6 Unicast Routing If a new switch becomes the stack master, the new master recomputes the IPv6 routing tables and distributes them to the member switches. While the new stack master is elected and is resetting, the switch stack does not forward IPv6 packets. If a new switch becomes the stack master, the stack MAC address also changes. When the IPv6 address of the stack is specified with an extended universal identifier (EUI) by using the ipv6 address ipv6-prefix/prefix length eui-64 interface configuration command, the address is based on the interface MAC address, and changing the MAC address changes the IPv6 address. See the "Configuring IPv6 Addressing and Enabling IPv6 Routing" section on page 36-11. Note If you configure the persistent MAC address feature on the stack and the stack master changes, the stack MAC address does not change for approximately four minutes. If the previous stack master rejoins the stack as a member switch during that time period, the stack MAC address remains the MAC address of the previous stack master. See the "Enabling Persistent MAC Address" section on page 5-19 in Chapter 5, "Managing Switch Stacks." These are the functions of IPv6 stack master and members: • Stack master: - runs IPv6 routing protocols - generates routing tables - distributes CEFv6 routing tables to stack members that use dCEFv6 - runs IPv6 host functionality and IPv6 applications • Stack member (must be running the advanced IP services image): - receives CEFv6 routing tables from the stack master - programs the routes into hardware Note IPv6 packets are routed in hardware across the stack provided the packet does not have exceptions (IPv6Options) and the switches in the stack have not run out of hardware resources. - flushes the CEFv6 tables on master re-election With IPv4 unicast routing, if the stack detects that the stack master is down and elects one of the stack members to be the new stack master, except for a momentary interruption, the hardware continues to forward packets with no protocols active. With IPv6, the switch does not continue forwarding packets. On election of a new stack master, the stack might need up to 60 seconds to recover all routes and resume forwarding traffic. IPv6 host functionality is supported on the stack master, and all IPv6 applications run on the stack master. SDM Templates Most Catalyst 3750 switches have one TCAM to store unicast routes, MAC addresses, ACLs, and other features. To allocate TCAM resources for different usages, the switch SDM templates prioritize system resources to optimize support for certain features. You select the template that best suits the switch environment by entering the sdm prefer global configuration command. For more information about SDM templates, see Chapter 8, "Configuring SDM Templates." 36-8 Catalyst 3750 Switch Software Configuration Guide OL-8550-02

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36-8
Catalyst 3750 Switch Software Configuration Guide
OL-8550-02
Chapter 36
Configuring IPv6 Unicast Routing
Understanding IPv6
If a new switch becomes the stack master, the new master recomputes the IPv6 routing tables and
distributes them to the member switches. While the new stack master is elected and is resetting, the
switch stack does not forward IPv6 packets. If a new switch becomes the stack master, the stack MAC
address also changes. When the IPv6 address of the stack is specified with an extended universal
identifier (EUI) by using the
ipv6 address
ipv6-prefix/prefix
length
eui-64
interface configuration
command, the address is based on the interface MAC address, and changing the MAC address changes
the IPv6 address. See the
“Configuring IPv6 Addressing and Enabling IPv6 Routing” section on
page 36-11
.
Note
If you configure the persistent MAC address feature on the stack and the stack master changes, the stack
MAC address does not change for approximately four minutes. If the previous stack master rejoins the
stack as a member switch during that time period, the stack MAC address remains the MAC address of
the previous stack master. See the
“Enabling Persistent MAC Address” section on page 5-19
in
Chapter 5, “Managing Switch Stacks.”
These are the functions of IPv6 stack master and members:
Stack master:
runs IPv6 routing protocols
generates routing tables
distributes CEFv6 routing tables to stack members that use dCEFv6
runs IPv6 host functionality and IPv6 applications
Stack member (must be running the advanced IP services image):
receives CEFv6 routing tables from the stack master
programs the routes into hardware
Note
IPv6 packets are routed in hardware across the stack provided the packet does not have
exceptions (IPv6Options) and the switches in the stack have not run out of hardware
resources.
flushes the CEFv6 tables on master re-election
With IPv4 unicast routing, if the stack detects that the stack master is down and elects one of the stack
members to be the new stack master, except for a momentary interruption, the hardware continues to
forward packets with no protocols active. With IPv6, the switch does not continue forwarding packets.
On election of a new stack master, the stack might need up to 60 seconds to recover all routes and resume
forwarding traffic.
IPv6 host functionality is supported on the stack master, and all IPv6 applications run on the stack
master.
SDM Templates
Most Catalyst 3750 switches have one TCAM to store unicast routes, MAC addresses, ACLs, and other
features. To allocate TCAM resources for different usages, the switch SDM templates prioritize system
resources to optimize support for certain features. You select the template that best suits the switch
environment by entering the
sdm prefer
global configuration command. For more information about
SDM templates, see
Chapter 8, “Configuring SDM Templates.”