The 'broadcasts' are just to allow us to get to a subset of the machines on the HDLC nets. I
suppose that they could be called IP multicasts, although the are not using the traditional
multicast addresses. The broadcasts addresses should never be generated outside of the 'gateway'
(we actually call these machines proxies). The gateway is actually used as a proxy for some
services, hence the need to be able to broadcast packets to some subset of the devices on the HDLC
nets (commands for a class of machines). The traffic that goes between the HDLC nets and the
ethernet is (at this point) all initiated from the machines on the HDLC nets, things like NFS
mounts. As I stated in a previous email, we have contemplated using the iptable NETMAP target to
directly map something like 10.192 on the ethernet WAN to 172.16 on the HDLC nets. But this will be
for the convenience of being able to then directly telnet into the machines on the HDLC nets, not
for sending 'broadcasts'.
Greg
Rick Jones wrote:
Greg Wilson-Lindberg wrote:
Ok, I can use route to add the various IP addresses that are on each
HDLC channel to the routing tables. There are a lot of machines, but
because the addresses are well known/formatted, generating the scripts
automatically won't be to bad. But how do I handle broadcast addresses
such as 172.16.255.255, 172.16.128.255, or 172.16.129.15 that need to go
out all of the HDLC channels?
How are those going to appear on the gateway's 10net interface in the first
place? I thought stuff like "directed broadcast" was verboten these days and
essentially unsupported by any stack. That is why I was asking if these were to
be broadcasts or perhaps IP multicasts - where IP multicasts *can* and do get
routed.
Please don't take this the wrong way, but on the surface, the setup you've
described sounds terribly kludged and so very brittle, and given the domain of
your email and a bit of reader imagination that is, well, troubling :)
rick jones
Oskar Berggren wrote:
2009/10/7 Rick Jones <rick.jones2@xxxxxx>:
Greg Wilson-Lindberg wrote:
Rick Jones wrote:
...
I have not fully parsed the manpage for the ip command, but it does have
tidbits which suggest being able to specify interfaces by name when
manipulating routing tables. If that is correct you should be able
to add
specific host routes pointing-out specific interface names if you are
indeed
forced to put assign the same IP address to each of the HCLC
interfaces on
the "gateway."
Yes,
ip route add x.x.x.x/x dev eth1
or similar works fine.
If you like, you can also use ip addr add x.x.x.x/32 dev eth1 to set
an ip-address without having the kernel automatically install a subnet
route. Then manage the routing tables complete by yourself.
/Oskar
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