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From: Martin Pauly (pauly_at_hrz.uni-marburg.de)
Date: Thu 17 Mar 2005 - 11:42:34 GMT


Hello Herbert,

> check with iproute2's 'ip' utility (ip addr ls, ip route ls, ...)
> to get a better 'understanding' what the legacy ifconfig
> utility does with interfaces, addresses and routes ...

well, the ip tools seem to do pretty much the same in this respect:

-------- start of transcript ----------------------
master22:~# ip addr sh
1: lo: <LOOPBACK,UP> mtu 16436 qdisc noqueue
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
2: eth0: <BROADCAST,MULTICAST,UP> mtu 1500 qdisc pfifo_fast qlen 1000
    link/ether 00:0e:0c:5c:53:75 brd ff:ff:ff:ff:ff:ff
3: eth1: <BROADCAST,MULTICAST,UP> mtu 1500 qdisc pfifo_fast qlen 1000
    link/ether 00:0e:0c:5c:53:74 brd ff:ff:ff:ff:ff:ff
    inet 192.168.1.18/25 brd 192.168.1.127 scope global eth1
    inet 137.248.1.53/25 scope global eth1
master22:~# ip route sh
137.248.1.0/25 dev eth1 proto kernel scope link src 137.248.1.53
192.168.1.0/25 dev eth1 proto kernel scope link src 192.168.1.18
default via 192.168.1.126 dev eth1
master22:~#
master22:~# ip addr add 137.248.9.13/27 dev eth0
master22:~# ip route sh
137.248.9.0/27 dev eth0 proto kernel scope link src 137.248.9.13
137.248.1.0/25 dev eth1 proto kernel scope link src 137.248.1.53
192.168.1.0/25 dev eth1 proto kernel scope link src 192.168.1.18
default via 192.168.1.126 dev eth1
master22:~# ip route del 137.248.9.0/27
master22:~# ip route sh
137.248.1.0/25 dev eth1 proto kernel scope link src 137.248.1.53
192.168.1.0/25 dev eth1 proto kernel scope link src 192.168.1.18
default via 192.168.1.126 dev eth1
master22:~# ip route add 137.248.9.0/27 dev eth0 src 137.248.9.13 table 2
master22:~# ip route add default via 137.248.9.30 dev eth0 src 137.248.9.13 table 2
RTNETLINK answers: Network is unreachable
-------- end of transcript ----------------------

And again, if I switch the order of processing and remove
137.248.9.0/27 dev eth0 proto kernel scope link src 137.248.9.13
_after_ building table 2, everything's fine (and yes, I also tried to use table 100
instead of table 2, just in case there was something special about it).

So 'ip addr add <my-ip/my-masklen>' also sets an appropriate route
in the main table which is a reasonable default. But it still isn't clear
to be why building the second table should depend on some entry
in the main routing table.

At least what we can learn from this is that the use of alias ethernet
interfaces (e.g. eth0:rst1) by vservers does not seem to make any difference.
BTW: Can I set up alias interfaces with the iproute2 tools?
ifconfig does it, ip <something> dev eth:<alias> always gives me an error.

Thanks for your help, anyway
Martin

-- 
  Dr. Martin Pauly     Fax:    49-6421-28-26994
  HRZ Univ. Marburg    Phone:  49-6421-28-23527
  Hans-Meerwein-Str.   E-Mail: pauly_at_HRZ.Uni-Marburg.DE
  D-35032 Marburg

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