Re: Multiple interfaces with the same IP address

[Rick Jones <rick.jones2@hp.com>]

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@hp.com>:
>>
>>> 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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