Jeroen Massar schreef:
On Sat, 2006-03-11 at 16:07 +0100, Steven LatrŽe wrote:
Hi all,
First of all thanks for the answers on my previous question (subject:
Neighbour discovery and more than one NIC) that helped a lot but my
problem isn't completely solved. There've been some changes in my
set-up. Is still have some PC's chained together like this:
PCA (eth 2) <---> (eth1) PCB (eth1) <--> (eth2) PCC (eth1)
This is a simple example but actually there are more pc's chained
together. The overall topology is some kind of tree-and-branch
topology.
I'm not working with Neighbour discovery addresses any more (only for
one specific subnetwork but that's not important). I have some kind of
dhcp script that tries to discover the topology, assigns the right
unique local unicast addresses and sets the routing tables correct.
Now the weird thing is the following: I can perfectly ping two pc's
that are neighbours (eg PCA en PCB). Now when I want to ping from PCA
to PCC it doesn't work UNTIL I have made a ping from PCB to PCC. From
that moment on pinging A and C is possible. The error I get before it
works is "Address unreachable" So after a while I have a pretty good
chance that I can ping all my pc's, but that waiting isn't right I
think.
Here is a short explanation of my routing tables (working on Debian
Linux)
Which Debian? Or more to the point which exact kernel version?
[..]
I'm using kernel version 2.4.31
and
fd9f:187c:6e81:3e::1:fe dev eth3 metric 1 mtu 1500 advmss 1440
fd9f:187c:6e81:3e::/64 dev eth1 metric 256 mtu 1500 advmss 1440
fd9f:187c:6e81:3e::/64 via fd9f:187c:6e81:3e::1:fe dev eth3 metric
1024 mtu 1500 advmss 1440
The interresting question here: Why are you point the same /64 towards
eth1 and to the eth3 via that nexthop?
This will, with some luck, "load-balance" or better said, randomly send
packets out over eth1 or eth3. Which causes the problem you explained.
Thanks for pointing out that problem! That was indeed a mistake.
Unfortunately it didn't solve my initial problem. I still get the same
ping problems.
BTW, why use Unique Local Unicast addresses anyway?
I have two reasons (but I'm a newbie so they can be wrong):
- I'm developing a dynamic network that still works even if there's a
link down. The network will reconfigure itself so that when a link is
down two independent networks will be formed. It is important that
although those networks can't communicate with eachother they still
have different network id's. I read that the unique local unicast
addresses must form a random network id and that was what I want.
- If I'm not mistaken the unique local unicast addresses are a
"semi-alternative" for the private IPv4 addresses. And the network I'm
developing is private.
Is there any reason why I shouldn't use those addresses?
Regards,
Steven
Greets,
Jeroen
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