Skip site navigation (1)Skip section navigation (2)
Date:      Fri, 28 Jan 2000 15:50:01 +0100
From:      Roelof Osinga <roelof@nisser.com>
To:        "Rodney W. Grimes" <freebsd@gndrsh.dnsmgr.net>
Cc:        Kuzak <kuzak@kuzak.net>, freebsd-stable@FreeBSD.ORG
Subject:   Re: Odd DoS
Message-ID:  <3891AC99.CC9F8D3@nisser.com>
References:  <200001281411.GAA81282@gndrsh.dnsmgr.net>

next in thread | previous in thread | raw e-mail | index | archive | help
"Rodney W. Grimes" wrote:
> 
> > ifconfig_ep1="inet 212.187.0.39 netmask 255.255.248.0"
>                                                   ^^^^^^
> Are you really supernetted here?  This could be a major part of
> your problem.  Don't you mean ``255.255.255.248''?

You had me going there for a second <g>. Though I'd written 5 bytes.
Alas, nothing so simple. That netmask is as it should be. Besides, it
is a totally different route, the messages have to do with the other
subnet.

> > #ifconfig_ep1_alias0="inet 194.134.130.170 194.134.128.1 netmask
> > 255.255.252.0"
> 
> The above won't even parse correctly by ifconfig, 2 ip's???? and
> again, is this network SUPERNETTED?  Or is the netmask suppose to
> actually be 255.255.255.252?

Not only parses it just fine, it is also as documented. As to being
supernetted, talk to the ISP's in question. Defining their network
is their responsability. These are both CATV networks.

Mind you, if you can provide an URL that explains 'being supernetted'
it will be appreciated. For as per RFC 1519

   This plan is primarily directed at the first two problems listed
   above.  We believe that the judicious use of variable-length
   subnetting techniques should help defer the onset of the last problem
   problem, the exhaustion of the 32-bit address space. Note also that
   improved tools for performing address allocation in a "supernetted"
   and variably-subnetted world would greatly help the user community in
   accepting these sometimes confusing techniques. Efforts to create
   some simple tools for this purpose should be encouraged by the
   Internet community.

I'm confused <g>. If it's to be interpreted as the (virtual) sum of
all the individual subnets, then yep, I'm supernetted. Twice <g>.

Can't see why you're so surprised. Surely it's a good thing compared
to octet, class based, route exploding manner? RFC 1519 seems to
think so.

> And you'll probably get even less if your really have an off by <<8
> in your netmask and you fix it...

Alas. But do see the archives. What happens is that the ARP daemon
can not handle the case where one MAC is coupled to two distinct
IP adressess, i.e. gateways. You're looking for complexity where
simplicity is all there is.

One GW is 212.187.0.39, the other 194.134.128.1. They're on different
nets. They don't have the same MAC address.

arplookup 194.134.128.1 failed: host is not on local network

is bogus. For 194.134.128.1 *is* on the local network, local to the
194.134.130.170/duh network in fact. It just isn't local to the
212.187/21 network.

> What does your routing table look like???

Routing tables

Internet:
Destination        Gateway            Flags     Refs     Use     Netif Expire
default            212.187.0.1        UGSc       66  4014481      ep1
10/24              link#1             UC          0        0      ep0
10.0.0.1           link#1             UHLW        1     1556      ep0
10.0.0.2           0:0:e8:ee:c8:fb    UHLW       20   932933      ep0   1016
10.0.0.3           0:40:95:4:37:2a    UHLW        2  1007505      ep0   1061
10.0.0.4           0:4f:49:0:8a:ba    UHLW        1   596948      ep0   1156
10.0.0.55          0:60:97:14:31:a7   UHLW        0      474      lo0
10.0.0.255         ff:ff:ff:ff:ff:ff  UHLWb       3    16681      ep0
127.0.0.1          127.0.0.1          UH          3   278986      lo0
194.134.130.170    0:60:97:e4:98:db   UHLW        0       67      lo0 =>
194.134.130.170/32 link#2             UC          0        0      ep1
212.187/21         link#2             UC          0        0      ep1
212.187.0.1        0:90:6d:e4:30:0    UHLW       65       68      ep1    946
212.187.0.37       link#2             UHLW        1     2330      ep1
212.187.0.39       0:60:97:e4:98:db   UHLW        0      915      lo0
212.187.7.255      ff:ff:ff:ff:ff:ff  UHLWb       0       62      ep1


Again, all this information and more - way more - is in the archives.
We - other we <g> - have been over this again and again. And now again
again. To no avail.

> I do this all the time to route between 2 subnets on the same
> physical ethernet on 1 physical interface on 1 box.  It works
> just fine, I don't get bottles of arplookup's unless I blow one
> of the netmask some place or a -interface route.

Ok, I've shown you mine now you show me yours. Yeah, have done that
too <g>. However, these settings:

inet 212.187.0.39 netmask 255.255.248.0 defaultrouter=212.187.0.1
inet 194.134.130.170 netmask 255.255.252.0 defaultrouter=194.134.128.1

are at least as advertised. The latter I've worked with for some
three years. I've also tested it as the only IF and not an ARP message in
sight. Same holds for the former as only IF. The poblem only occurs
when one of the is aliassed. Doesn't matter which one.

In your case, have both subnets different gateways for their 
respective supernets? E.g. the EuroNet network has some servers
that only be gotten at when coming from a 194.134/16 range. Though
their INN supports the password option.

Silly thing is that what I'm doing here is akin to what I was doing
in '93 with the KA9Q NOS. With it it did work. This is not to say
I'm not doing anything wrong this time, just that it can work.

Roelof

-- 
Dog's house @ http://cairni.com/


To Unsubscribe: send mail to majordomo@FreeBSD.org
with "unsubscribe freebsd-stable" in the body of the message




Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?3891AC99.CC9F8D3>