Consider, you have two machines A and B. A has a leased
line to site C, B has a demand dialled ISDN link on hot
stand by (i.e. configured and ready to dial). A's interface
should be preferred over B's so B's is configured with a
higher metric so it only gets traffic if A dies. Is that
reasonable?
Diald uses a proxy interface with higher metric than the
real interface. This simplifies changing things around
as the link goes up and down (in theory :-) )
2. It is not possible to change the BROADCAST and POINTTOPOINT
flags on an interface. This appears to be enforced in
dev_change_flags in the kernel net code. It is not unreasonable
for ordinary ethernet interfaces to be used as a fast p-t-p
link between two systems in order to reduce traffic on the
open network. (This implies that there must be a way to prefer
the p-t-p link over the main net interface. Metric again?)
3. I don't know how to set a metric on a route with "ip". Nor does
"ip" appear to display route metrics on routes created with "route"
although "netstat" does.
4. Using an ippp interface I can manage to send out packets with
a source address of 0.0.0.0.
The interface is configured with an ifconfig and a default
route added through it with "route add default dev ippp0".
"ip route" tells me:
10.1.254.1 dev ippp0 proto kernel scope link src 172.16.1.8
default dev ippp0 scope link
Packets routed *through* the local host are fine (as expected).
Packets originating *from* the local host are sent on ippp0
correctly but have a source address of 0.0.0.0 (as reported
by the remote host).
If I use "ip route add default dev ippp0 src 172.16.1.8" instead
of using "route" "ip route" tells me:
10.1.254.1 dev ippp0 proto kernel scope link src 172.16.1.8
default dev ippp0 scope link src 172.16.1.8
Now locally originating packets go out with the correct source
address. It looks like a problem with routing through a p-t-p
but could be an ISDN problem (I haven't been able to reproduce
the problem over async PPP for instance). This is the ISDN
code from ftp.suse.com dated 990128 not the old stuff in the
kernel.
N.B. I need to use "ip" to set the src addr on the default
route but I can only set a metric if I use "route" :-(.
--
A train stops at a train station, a bus stops at a bus station.
On my desk I have a work station...
.----------------------------------------------------------------------.
| Mike Jagdis | Internet: mailto:mike@roan.co.uk |
| Roan Technology Ltd. | |
| 54A Peach Street, Wokingham | Telephone: +44 118 989 0403 |
| RG40 1XG, ENGLAND | Fax: +44 118 989 1195 |
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