RE: IP Aliasing under Red Hat 5.0 (Weird problem)

Glynn Clements (glynn@sensei.co.uk)
Mon, 3 Aug 1998 23:07:28 +0100 (BST)


Hill.Robertson@stn.siemens.com wrote:

> We have 4 class C addresses assigned to Michiana.net,
> 208.226.220.0-223.0. We have these variably subnetted. The class C we
> are dealing with is 208.226.220.0, here is how it is subnetted out:
>
> 208.226.220.0/30 (Unusable, all 0's and 1's)

Subnet 0 should be usable unless you have some really ancient routers.

> 208.226.220.4/30
> 208.226.220.8/29
> 208.226.220.16/29
> 208.226.220.24/30
> 208.226.220.28/30
> 208.226.220.32/27
> 208.226.220.64/26
> 208.226.220.128/26 (** This is the subnet we are working with in this issue **)
> 208.226.220.192/27

> 208.226.220.224/27

This corresponds to the range .224 to .255, which overlaps your final
subnet. This may or may not be an issue.

> 208.226.220.252/30 (Unusable, all 0's and 1's)

Similarly, the top subnet should be usable.

> - The only host numbers that exhibit this problem are:
>
> 135:10000111
> 136:10001000
> 143:10001111
> 144:10010000
> 151:10010111
> 152:10011000
> 159:10011111
> 160:10100000
> 167:10100111
> 168:10101000
> 175:10101111
> 176:10110000
> 183:10110111
> 184:10111000

Hmm. That's 10xxx000 and 10xxx111.

It looks to me as if something somewhere thinks that the netmask is
/29 (255.255.255.248). This would result in these addresses being
treated as either network (000) or broadcast (111) addresses.

> Does this help?

Maybe.

> Is there more information that you need?

The output of `ifconfig' and `route -n' may be of use.

-- 
Glynn Clements <glynn@sensei.co.uk>
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