Total Control MP/16, Operator'S Manual

Page: 59 / 182

The NMC MIB 3-23
NMC Authorized Access List
By default, the NMC authorized access table is empty. In this state,
there is no restriction on which management stations may manage
the chassis. Once a row is added to the authorized access table,
only management stations whose IP addresses pass the
authorization validation against the table are permitted access to
the NMC for the purposes of network management.
The table is indexed by IP address (nmcAuthAccIpAddr). The
other objects in each row include a required subnet mask
(nmcAuthAccNetMask) and optional textual description
(nmcAuthAccDescr). To add a row, simply set a value other than
0.0.0.0 for nmcAuthAccNetMask with the desired index.
If the Network Manager wishes, set a description in
nmcAuthAccDescr to describe the access allowed by the given row.
To delete the row, simply set nmcAuthAccNetMask to 0.0.0.0.
Note that a maximum of 10 rows may be added to this table.
The NMC performs IP address authorization validation by the
process described below.
1
Take the source IP address of the inc oming IP packet and
perform an "and" operation on it and the value of
nmcAuthAccNetMask for the first row in the authorized access
list.
2
Compare this "anded" value with the value obtained by
performing an "and" on the nmcAuthAccIpAddr with
nmcAuthAccNetMask for the same row.
♦
If the two values match, the IP packet passes the
authorization test and is passed to higher protocol layers
for further processing.
♦
If the values do not match, the next row in the authorized
access list is verified by the same procedure listed above.
If the end of the table is reached without a match, the IP
packet fails the authorization test and it is discarded. The
value of ipInDiscards is incremented and the IP packet is
discarded.
ICMP packets are not validated against the above checks for the
Network Manager’s convenience. It is often helpful to use an
ICMP echo packet to check basic network health from any