> Perhaps this is a problem with terminology. On one machine if I have
>
> 192.168.100.33. 192.168.100.66, 192.168.100.97 all with the subnet mask
> 255.255.255.224 the rip updates from the machine contain information
> about the various subnets. This would indicate to me that "RIP" *does*
> understand subnetting. Are you saying that the packets on port 520 are
> *not* RIP updates?
>
> mj
Here is a small part of RFC 1058 :
"When a host evaluates information that it receives via RIP, its
interpretation of an address depends upon whether it knows the subnet
mask that applies to the net. If so, then it is possible to
determine the meaning of the address. For example, consider net
128.6. It has a subnet mask of 255.255.255.0. Thus 128.6.0.0 is a
network number, 128.6.4.0 is a subnet number, and 128.6.4.1 is a host
address. However, if the host does not know the subnet mask,
evaluation of an address may be ambiguous. If there is a non-zero
host part, there is no clear way to determine whether the address
represents a subnet number or a host address. As a subnet number
would be useless without the subnet mask, addresses are assumed to
represent hosts in this situation. In order to avoid this sort of
ambiguity, hosts must not send subnet routes to hosts that cannot be
expected to know the appropriate subnet mask. Normally hosts only
know the subnet masks for directly-connected networks. Therefore,
unless special provisions have been made, routes to a subnet must not
be sent outside the network of which the subnet is a part."
I think the last line is self explanatory about the fact that RIP does not
know about subnet.
Another point is if you look at the format of a RIP message (without the
header), you can see that there is no entry for the subnet mask :
+------------------------------------+
| IP address |
+------------------------------------+
| (must be zero) |
+------------------------------------+
| (must be zero) |
+------------------------------------+
| metric |
+------------------------------------+
and in RIP v2
+------------------------------------+
| IP address |
+------------------------------------+
| subnet mask |
+------------------------------------+
| next hop IP address |
+------------------------------------+
| metric |
+------------------------------------+
Eric
References:
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