IPv6 and coniguring it on a Catalyst 4500 L3 Switch

eduarddav · ‎10-09-2013

In order to configure something like this i first need to understand something - i have read a lot about IPv6 but i didn't understand something:

This is the stature of an IPv6 address, and the confusing part to me is the 0012 - the subnet.

2001:0db8:3c4d:0012:0000:0000:1234:56ab

Global prefix Subnet interface ID

I need to define IPv6 on multiple devices so i need to make sure that i address them correctly, and I obviously don't understand it correctly as I think of it as SM but there is an option to add an actual SM using the regular /70 and so on, and there are values in this field that don't coincide with being a SM – like0 or ffff or ffe0 and so on, so please explain this to me.

* i defined IPv6 address on an XP Client with the IP of 2001:10:10::85. There is no option to define prefix length so i don't know which Subnet Mask it's using. According to this address there is no subnet field set so i don't know what SM it thinks it is (i was instructed to define it like this).

* I have an F5 that was defined with the IP 2001:10:10::199 and with a subnet of ffff:ffff:ffff:ffff:0:0:0:0:0 which i have no idea what it means - what is this SM?

* And now i have to setup a Catalyst 4500 to act as the Gateway for this network but i don't know which Subnet Mask to set for its address - 2001:10:10::81

Also, after we can figure it out, i will appreciate some info on what has to be defined on the switch - i know that ipv6 enable has to be defined on the interface vlan that i set to use ipv6 and ipv6 unicast-routing has to be activated on the global.

But is there anything else - we configure the IPs of the client manually and set the DNS manually - so are there other things that have to be setup?

Thanks

Harold Ritter · ‎10-09-2013

Hi Edi,

> I need to define IPv6 on multiple devices so i need to make sure that i address them correctly,

> and I obviously don't understand it correctly as I think of it as SM but there is an option to add

> an actual SM using the regular /70 and so on, and there are values in this field that don't coincide

> with being a SM – like0 or ffff or ffe0 and so on, so please explain this to me.

In IPv6, you do not use a subnet mask but rather a prefix length (i.e /32, /48, /64, etc). Generally speaking, you will assign a /64 to an interface. The /64 length is required if you use stateless address autoconfiguration (SLAAC) but is also recommended in general.

> * i defined IPv6 address on an XP Client with the IP of 2001:10:10::85. There is no option to define

> prefix length so i don't know which Subnet Mask it's using. According to this address there is no subnet

> field set so i don't know what SM it thinks it is (i was instructed to define it like this).

You should be able to specify the prefix length with Windows XP.

> * I have an F5 that was defined with the IP 2001:10:10::199 and with a subnet of ffff:ffff:ffff:ffff:0:0:0:0:0

> which i have no idea what it means - what is this SM?

The subnet mask of ffff:ffff:ffff:ffff:0:0:0:0 is basically expressed as /64 in the IPv6 context. So the 2010:10:10::199/64.

> * And now i have to setup a Catalyst 4500 to act as the Gateway for this network but i don't know

> which Subnet Mask to set for its address - 2001:10:10::81

This would be configured as "ipv6 address 2001:10:10::81/64" in IOS.

> Also, after we can figure it out, i will appreciate some info on what has to be defined on the switch -

> i know that ipv6 enable has to be defined on the interface vlan that i set to use ipv6 and

> ipv6 unicast-routing has to be activated on the global. But is there anything else - we configure

> the IPs of the client manually and set the DNS manually - so are there other things that have to be setup?

It depends what you want to do and on the topology but these commands should be enough to get you started and to do routing between local interfaces.

Regards

eduarddav · ‎10-10-2013

Hi,

I obviously don't understand something about subletting in IPv6 - how does ffff:ffff:ffff:ffff:0:0:0:0 equal /64, and what does prefix length mean? How is it okay to have values of 0 or ffff in the subnet files that re supposed to represent this "prefix length" - the address is 128bit long so the maximum prefix length should be 128.

Thanks

cadet alain · ‎10-10-2013

Hi,

you've got 4 groups of 16 bits all set ton 1s( 1 hex character is 4 bits and so f is 1111) so 4 times 16=64

Regards

Alain

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Harold Ritter · ‎10-10-2013

Hi Edi,

The following paper from one of my colleagues would definitely be helpful in understanding IPv6 subneting.

https://supportforums.cisco.com/docs/DOC-17232

Regards