On Thu, Mar 24, 2005 at 01:15:42PM +0000, Dominic Hargreaves wrote: > I have a machine with multiple IPv6 addresses (all in the same prefix) > assigned to its main network interface (eth0). This works fine, apart > from the binding of source addresses for outgoing connections on this > machine. > Under IPv4, one would typically set this up with interface aliases: > ifconfig eth0 my.main.ip > ifconfig eth0:foo my.foo.service.ip [trim] > Lastly, section 5.3 of the iproute manual claims that "an IP address > becomes secondary if another address with the same prefix bits already > exists" (and that a secondary address is not used when selecting the > default source address of outgoing packets. > Howver: > dom@urchin:~$ ip -6 addr show dev eth0 primary > 2: eth0: <BROADCAST,MULTICAST,UP> qlen 1000 > inet6 fe80::2e0:18ff:fe07:c2b7/64 scope link > inet6 2001:1b40:0:1000:c1c9:c849:0:1/64 scope global > inet6 2001:1b40:0:1000:c1c9:c849:103:e801/64 scope global > dom@urchin:~$ ip -6 addr show dev eth0 secondary > Some further points: > - If I add a third address to the interface, that gets used instead; > I would guess that the last address is always used > (rather than the first). > - Assigning extra addresses with labels such as eth0:foo makes no > difference. Under ipv4, eth0:foo makes that IP address secondary. If you use ip addr add <ipv4> it'll also be primary. Mind you, in IPv4 it _does_ successfully pick the lowest primary IP address. You can add 'secondary' to the end of your ip -6 add command to make it secondary, then it shouldn't be a candidate for source addressing except when specified (eg. ping) Basically, somewhere along the line, Linux gained the ability to have multiple primary IPs on a single interface and prefix. -- ----------------------------------------------------------- Paul "TBBle" Hampson, MCSE 8th year CompSci/Asian Studies student, ANU The Boss, Bubblesworth Pty Ltd (ABN: 51 095 284 361) Paul.Hampson@Anu.edu.au "No survivors? Then where do the stories come from I wonder?" -- Capt. Jack Sparrow, "Pirates of the Caribbean" This email is licensed to the recipient for non-commercial use, duplication and distribution. -----------------------------------------------------------
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