3750 /48 IPv6

[CobbyJ]

Hello,

We are trying to setup a /48 IPv6 in our 3750 but doesnt seem to like it and doesnt pass it and stops it all pinging and working on the internet but works internally for some strange reason.

Any ideas? i have asked our uplink supplier to check and confirm but also seen this.

https://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst3750x_3560x/software/release/12-2_53_se/configuration/guide/3750xscg/swipv6.html

[Seb Rupik]

Hi there,

Can you eleborate a bit on the statement "doesnt seem to like it" ? For staters have you changed the SDM templte and restarted the switch:

sdm prefer dual-ipv4-and-ipv6 routing

cheers,

Seb.

[CobbyJ]

The current template is "desktop IPv4 and IPv6 default"

I meant when setting a ipv6 range to  /48 or anything higher than a /64 it no longer works from outside of our network (this is a public ipv6 range) but does work internally within our network.

[balaji.bandi]

I meant when setting a ipv6 range to  /48 or anything higher than a /64 it no longer works from outside of our network (this is a public ipv6 range) but does work internally within our network.

This is not clear, can you explain or show us what is not working with the example ?

[CobbyJ]

its very had to show you or descripe.

so we have tried with a vlan and a static route to a pfsense

so for example - that doesn not work outside of our internal network - we are unable to ping it from outside and doesnt work as a gateway and unable to ping to it and from it

interface vlan 500
 ipv6 address 2a05:f81:45::1/48

This for example with a /64 does work and ping ouside of our network and internally

interface vlan 500
 ipv6 address 2a05:f81:45::1/64

[Harold Ritter]

Hi @CobbyJ ,

You definitely need to configure a /64 on the Vlan interface if you want the clients to use Stateless Address Auto Configuration (SLAAC) to auto configure themselves. Configuring a /48 will not work.

Regards,

[CobbyJ]

We dont want to use stateless address as they are set manually.

Just want it to work with the /48

We have now set it as a static route to a pfsense but again will only work on the internet out side of our local network - setting it as a /64 does work though and pings.

Inside our network the /48 pings fine and cant find any issue.

the /48 static route is being advertisded via BGP

[Harold Ritter]

Hi @CobbyJ ,

Even if you do not use SLAAC, it is still a best practice to assign a /64 to user facing interface. Can you explain why you need to assign the full /48 to the Vlan interface?

Regards,

[CobbyJ]

Hello Harold.

I totally agree with you and say we should use a /64

Its the client of the /48 we are hosting who wishes to do the entire /48 which in my mind is insane, but still dont see any reason why its not working externally.

[Harold Ritter]

Hi @CobbyJ ,

> Its the client of the /48 we are hosting who wishes to do the entire /48 which in my mind is insane

I doubt they will be able to use all that space LOL

> but still dont see any reason why its not working externally.

Although I do not see anyone doing it, I agree that in theory it should work. Can you provide the configuration.

Regards,

[CobbyJ]

Its just a simple static route right now

(changed the ip's for security)

ipv6 route 2a05:f81:45::/64 2A05:2BB5:1:1::10

If i do the following as a /48 as i said it pings internally but nothing externally on wan, it is being sent via ospf v3 to BGP and the uplink provider is recieving the full /48 prefix and have checked everything their side.

[Harold Ritter]

Hi @CobbyJ ,

In a previous post you stated that the /64 or /48 was directly applied to the Vlan interface. Where is the static route configured? Can you tell us a bit more about the overall topology?

Regards,

[CobbyJ]

sorry for the confusion, yes at first we tried it as a vlan to see if that was the issue, but now we are trying it as a static route which is having the same issues.

[Harold Ritter]

Hi @CobbyJ ,

As mentioned in my previous post, we need a bit more information about the topology (interaction between ospfv3, BGP, static route) to be able to help.

Regards,