How to set IPv6 Gateway to an interface & Set DHCPv6 starting/ending IP

[lnsilva]

Hello,

I'm new kinda new about IPv6 and configuration of cisco routers, so I need some help.

I need to set an starting and ending IP to the DHCPv6, but I can't find how. I did read that you can't do that in DHCPv6 because the amount of IP that it manage (or something like that) and set a range does not make sense. I don't really understand that, because what if I want to assing a ceratain range of IP's, for example (in classic DHCP ipv4):

Start IP: 192.168.1.100/24

End IP: 192.168.1.200/24

For whatever reason I want that, because the other IP's are reserved for future devices or something, so you can't do that in DHCPv6?

The other task is to set a default gateway with IPv6 address, to the interface that is DHCPv6. And read the something like above, you can't because get and automatic gateway or something like that, again, an example with IPv4

Router A => First router and the one connected to Internet

Router B => Router in a LAN, and when some device needs to connect to internet the package goes like:

Device => Router B => Router A => Internet

I don't know where is the "problem", you can't do that kind of "classic network design" with IPv6 or what?

P.S: Sorry for my bad english, hope you understand me

[Hector Gustavo Serrano Gutierrez]

Hi lnsilva@outlook.es,

Some points to take into consideration:

1. There is currently no equivalent of 'ip dhcp excluded-address' for IPv6 in Cisco IOS.
2. DHCPv6 does not provide Default-Gateway information to end-hosts. The end-hosts get the Default Gateway information from the ICMPv6 RA (Router Advertisement) packet sent by the local Router.
3. When having 2 more Routers on the same LAN, you can either use HSRP for IPv6 or change the priority of the Default Gateway information included in the ICMPv6 RA maessage on one of the Routers.

R1(config)#interface fastEthernet 0/0
R1(config-if)#ipv6 nd router-preference ?
  High    High default router preference
  Low     Low default router preference
  Medium  Medium default router preference

Regards.