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Re: Gigabit Linux Routers

  • From: Ingo Flaschberger
  • Date: Fri Dec 19 17:29:20 2008
Dear Joe,

Yes, but the point was that the feature was listed as "simple traffic
shaping."  You can do *complicated* traffic shaping too, which was the
reason I commented on that.  Usually the ability to do complicated
traffic shaping means you can do simple traffic shaping too.  ;-)


with linux?
really?

Mmm, generally, it looks to me like it works, but the above is the
entirety of my testing, so I could easily be wrong.


you have ospf between this 2 boxes?
show me them routing table.
do a failover and show the routing table again,

*) carp is i bound, carp-dev line openbsd is in development
 	(not shure if already stable)


You mean inbound?  Well, yes.  That's reasonably practical.  It isn't
entirely clear what other paradigms would look like (i.e. if the host
system didn't have a native address on the wire), though several ideas
spring to mind.

Am I correct in assuming that you mean to have no native interface on
the network in question, and only a CARP interface?  Or am I reading in
between the lines incorrectly?

only carp-int has the ip's.

*) if carp switch over:
 	t=0: A is master, has route 192.168.0.1/24
 	     B has route 192.168.0.1/24 via ospf
 	t=1: A goes down, route disappear (need linkstate in ospf)
 	t=2: B carp takes over 192.168.0.1/24
 		B can not add 192.168.0.1/24 route as it is still
 		known via ospf
 	t=3: B gets update to remove route 192.168.0.1/24 via ospf
 	t=4: 192.168.0.1/24 route has disappeared, failover broken.

with ucarp, some special scripts and source code changed I was able
to handle this situation, but not with carp and ospf (at least at
freebsd 6.3)


I agree that this is a problematic scenario.  FreeBSD 5.* and 6.* are
pretty worthless to us, so we've pretty much jumped from 4 to 7, and
so my knowledge of the networking improvements in between are limited.

I have not yet tested freebsd 7, as the multicast kernel interface changed and quagge ospf breaked. also I need(ed) a stable platform.

Under FreeBSD 4, there is indeed a great deal of pain associated with
routes coming in via a routing protocol that are also theoretically
available on a directly-attached interface.

I just tried downing rtr1: vlan20 on the above (which is FreeBSD 7,
obviously) and from rtr1's PoV the network did move correctly to an
alternate route via OSPF, but upon re-enabling the vlan20 interface,
the OSPF route remained.  Now, it seemed to "all work again" when I
did the following:

yes, thats the problem.

# ifconfig vlan20 up
# route delete -net 206.55.68.192
# ifconfig vlan20 inet 206.55.68.195 netmask 0xffffffe0


I have changed ucarp todo so, but you also need
gratious arp and such stuff to get a real, flawless failover.

which re-established the local link.  That's not ideal, but it is a lot
better than FreeBSD 4, where things were just breaking all over if you
did "strange" things like this.

For most important things around here, we use OSPF with stub routes so
the failure of a particular ethernet is not necessarily of great concern,
but it would be nice to see things like this know how to DTRT.

DTRT?

Kind regards,
	Ingo Flaschberger