Hello,
Halassy Zoltán a écrit :
My ISP own the address space 1234::/16
I own the address space 1234:100::/32
My ISP gave me the extra address 1234:0:ffff:100::2 (lower than my
address space) from their address space, and using 1234:0:ffff:100::1 as
gateway. This subnet is only /126 large.
Later you wrote /112. Is it /126 or /112 ?
My ISP forbids to use this
extra IP for global purposes, it's only for routing, they even firewall
it out, when i try let's say ping6 ipv6.google.com with that address.
Ok. It serves as a kind of local prefix.
eth0 has global address 1234:0:ffff:100::2
Default gateway is 1234:0:ffff:100::1
eth1 has global address 1234:100::1
Computers behind eth1 using 1234:100::1 as default gateway, their
connectivity is fine.
And here started my problem, on the gateway i would like to maintain a
service, eg. NTP.
programs picks up the address 1234:0:ffff:100::2 so they won't reach
their destination.
So i added the ip 1234:100::1 to eth0 too (noticed that programs picks
up the last added IP address mostly),
Yes, the IPv6 default source address selection in the kernel is kinda
tricky.
and then removed the subnet
routing rule to prevent the comp to search hosts belonging that subnet
over eth0.
This should not be necessary if you add only a single address (/128) to
eth0, not a subnet.
I was thinking on different things, i know the kernel can hold multiple
routing tables
Yes, but I do not see how this might help here. The problem is source
address selection, and as you noticed, the 'src' option in ip -6 route
is ignored.
Here is a workaround which may work. IIUC 1234:0:ffff:100::2 is used
only for routing : the ISP's router uses it as the nexthop to route your
prefix. Since your box has IPv6 forwarding enabled, you can use ND
proxy, which does the same as ARP proxy in IPv4.
Do not add 1234:0:ffff:100::2 to eth0. You do not even need to add an
IPv6 global address to eth0 : the box will use any other available
global address (i.e. the one on eth1) when communicating on eth0. Instead :
# add a ND proxy entry for 1234:0:ffff:100::2
ip -6 neigh add proxy 1234:0:ffff:100::2 dev eth0
# add a route to the link subnet 1234:0:ffff:100::/126 (or /112)
ip -6 route add 1234:0:ffff:100::/126 dev eth0
# add the default route
ip -6 route default via 1234:0:ffff:100::1 dev eth0
For kernels 2.6.19 and above, you also need to enable proxy ND on eth0 :
sysctl -w net/ipv6/conf/eth0/proxy_ndp=1
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