confused with ipv6 routing
 

hi all

i need help with sorting out my ipv6 routing question. I find the whole IP thing really confusing and inclusion of IPv6 really doesn't help.

Here is what I got.

I got 3 /64 ipv6 blocks. A/64, B/64, and C/64. I have 3 nodes: a linux blade cluster, (LBC) a Quagga router and the switch.

The network looks something like this: LBC <--> Quagga <--> switch.

I have assigned A::5/128 to LBC as a virtual IP, meaning that as far as the rest of the world is concerned, LBC has A::5 while within the LBC, it can be whatever.

My goal is to have A::5/128 pingable from the switch.

Now for IPv4, to do something of this is actually rather easy. Like this:
a IPv4 vip would be defined, and attached to the blade cluster with a /30 subnet, and one side of the /30 would be on the LBC, while the other side would be on the Quagga router.

Then the quagga router would say, the /30, route through my default gw. which would be in the same subnet as the switch. say a /28.

The I just have to define, on the quagga, this IPv4 VIP should route through my /30, and on the switch my IPv4 VIP should route through my quagga's default gw.

After that, everything is pingable and i get a workable system.

but with IPv6, and the introduction of link local addresses, i am now confused as to what to route where.
in theory, i should take above example, replace ipv4 with ipv6, and it should work. but i am having a lot of problems with that. I know link local are valid only within their context, i have to ping from a specific network interface, unlike ipv4.

can someone help me sort this mess out?

thanks guys

Yes, that's exactly what you should do.
Could you be a bit more specific?

Link-local addresses are not relevant to routing issues, as they are just that: link-local. You can safely ignore them when you're configuring routing.

As long as you're not accessing the link-local addresses, IPv6 works the same way as IPv4. The main difference when it comes to routing is that every IPv6 router advertises itself on the network with ICMP6 Router Advertisement messages. Other hosts can pick that up automatically or query the network with ICMP6 Router Solicitation messages.

actually from the LBC to the Quagga it is done via ospf, so i need the link local. but that isn't the issue right now.

quagga and my switch seems to be having a fit. they are both under /64, but can't ping each other, even though the tcpdump shows the request and reply, and Neighbourhood Discovery on the switch shows the proper ips/mac and everything.

I'm not saying you don't need link-local addresses; after all, they are used as source addresses for most (all?) link-local multicast traffic. I'm just saying you don't have to include them in your configuration anywhere, as they are generated and used automatically.

If the switch and the Quagga router both have a statically assigned IPv6 address in the same /64 network and ND works as it should on both hosts, you should definitely be able to ping from one host to the other. I'd check the iptables rules and the /proc/sys/net/ipv6/conf/* settings on the Linux host, and check for ACLs that may exist on the switch.

I remember that an OSPF configuration error once caused a Quagga router to seemingly drop off the network, and I was unable to ping the router from other hosts on the same subnet/segment until the error was corrected. I've never been able to figure out exactly how that could happen, but you may want to stop the ospf6d daemon until you've verified that the IP configuration itself is working.

hey, we fixed that problem by unconfiguring and reconfiguring the switch's corresponding vlan.

lol, 4 hours of debugging.

now we finally seem to be on the home stretch.

I got my LBC, Quagga and Switch all pingable between each other. But LBC can not ping straight to Switch.

LBC can ping quagga, quagga can ping switch. lbc can not ping switch or vice versa.

Is the Quagga router sending out Router Advertisements?

And is IPv6 routing enabled? The output of cat /proc/sys/net/ipv6/conf/all/forwarding should be 1.

hey

we fixed it. quagga did not have ipv6 forwarding enabled.

man quagga sucks.

f@#$%@#%#$^ quagga.

thanks for your help.
really appreciate it. :D
now i need to document this.

I guess it's just faithfully emulating a Cisco router. IPv6 routing is disabled by default in Cisco IOS as well.