NDP DRP vs HSPv6

[CSCO11598534]

Hello all,

In a IPv4 LAN section where we have two routers, we offer HSRP VIP towards end-hosts for redundancy purposes.

In a IPv6 LAN section, what is the best equivalent solution? 

a) Use NDP DRP with different preference value (High/Medium) between the two routers? Are we sure that all Linux/Windows servers "understand"  DRP?

b) Use HSRPv6 instead? If yes, should we use Link Local or Global Unicast Address as VIP ?

Thank you

[Harold Ritter · Accepted solution]

Hi @CSCO11598534 ,

>a) Use NDP DRP with different preference value (High/Medium) between the two routers? Are we sure that all Linux/Windows servers "understand"  DRP?

I have seen very few customers using this approach.

> b) Use HSRPv6 instead? If yes, should we use Link Local or Global Unicast Address as VIP ?

From my experience working with IPv6, I can say that the vast majority of customers uses HSRPv6 for this purpose, if they are already using HSRP for v4. The 

LLA is used by default for the VIP. The use of a GUA for the VIP is only for specific use cases. 

Regards,

[CSCO11598534]

Thank you.

In our situation we have only one router (dual-stack) and we intent to add a second one for redundancy.

For sure we will use HSRPv4. Do you propose to also use HSRPv6 ?

[Harold Ritter]

Hi @CSCO11598534 ,

I certainly do.

Regards,

[CSCO11598534]

Can you please mention a real life reason where you would use GUA as VIP? 

Thank you.

[Harold Ritter]

Hi @CSCO11598534 ,

One use case I came across was that a router was configured with a static route pointing to the VIP. This router could not set the static route next hop to a link local address. It needed to be a ULA or GUA.

In my case it was a router, but it could also be a FW or any other network device needing to point a static route to the VIP.

Regards,

[CSCO11598534]

A final question: why some people are in favor of hardcoding the LLA of the DG as fe80::1 ? 

The end hosts will automatically learn the eui-64 LLU with no problem, right?

Is it just for not having to type it when they try pinging?

What do you recommend?

[CSCO11598534]

*eui-64 LLA

[Harold Ritter]

Hi @CSCO11598534 ,

Yes, hardcoding the LLA makes it more predictable. It is useful if you are going to have static routes of bgp sessions using the LLA instead of the GUA. In your scenario, I would just use the default.

Regards,

[CSCO11598534]

Hello again.

Lets say that we want to use eui-64 LLU in HSRPv6  as DG (#standby 1 ipv6 autoconfig).

But we also want to statically assign a GUA in the end client.

Can we do that e.g in a Windows client? Can we assign only the IPv6 address and leave the DG blank? Will it auto-use the router's HSRPv6 LLA without hardcoding it?