Network Toolkit – Enabling IPv6 on Cisco Catalyst 3750 Devices

As a part of my IPv6 series, I started with routers and then worked my way out from there. I was caught a little offguard when I tried to bring up my 3750 on IPv6 and didn’t find any of the commands for IPv6 present in the switch. I check and made sure that I had the right version of code installed. A little more work and I found the problem. The 3750’s are optimized for maximum performance and that involves disabling IPv6 support to allow the TCAM memory to be as responsive as problem with IPv4. You can see where you stand by doing a show sdm prefer at the enable prompt of the switch. You will probably see something like this –

3750#sh sdm prefer
The current template is “desktop default” template.
The selected template optimizes the resources in
the switch to support this level of features for
8 routed interfaces and 1024 VLANs.
number of unicast mac addresses: 6K
number of IPv4 IGMP groups + multicast routes: 1K
number of IPv4 unicast routes: 8K
number of directly-connected IPv4 hosts: 6K
number of indirect IPv4 routes: 2K
number of IPv4 policy based routing aces: 0
number of IPv4/MAC qos aces: 0.5K
number of IPv4/MAC security aces: 1K

You can see the different sdm options by using the following command –

3750(config)#sdm prefer ?
access Access bias
default Default bias
dual-ipv4-and-ipv6 Support both IPv4 and IPv6
routing Unicast bias
vlan VLAN bias

Before I go too far, I probably should define with SDM stands for. If you have been working with ASA’s and routers, you will probably think it means Security Device Manager. Not in this case, it actually stands for switching device manager. To enable IPv6 support, you will need to use this command – sdm prefer dual-ipv4-and-ipv6, save the config and reboot the switch.

After you have changed modes in SDM, you should see this when you next check the switch –

3750#show sdm prefer
The current template is “desktop IPv4 and IPv6 default” template.
The selected template optimizes the resources in
the switch to support this level of features for
8 routed interfaces and 1024 VLANs.

number of unicast mac addresses: 2K
number of IPv4 IGMP groups + multicast routes: 1K
number of IPv4 unicast routes: 3K
number of directly-connected IPv4 hosts: 2K
number of indirect IPv4 routes: 1K
number of IPv6 multicast groups: 1.125k
number of directly-connected IPv6 addresses: 2K
number of indirect IPv6 unicast routes: 1K
number of IPv4 policy based routing aces: 0
number of IPv4/MAC qos aces: 0.5K
number of IPv4/MAC security aces: 1K
number of IPv6 policy based routing aces: 0
number of IPv6 qos aces: 0.5K
number of IPv6 security aces: 0.5K

For more information, check out this document – http://www.cisco.com/en/US/products/hw/switches/ps5023/products_tech_note09186a00801e7bb9.shtml

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