ACCULINK 317x E1 DSU/CSU
E-6
December 1996
3170-A2-GB20-20
IP Group – “ipRouteTable” Object (ip 21)
The routing table used by the E1 DSU/CSU is
supported as a read/write table. Entries in this table may
be added, deleted, or changed. You should exercise great
caution when adding or modifying routes in the
ipRoutingTable. In general, it should not be necessary to
add or modify routes in the E1 DSU/CSU. In those cases
where it is deemed necessary, the routes should only be
added to the connected device (i.e., the device closest to
the destination). Internal routing mechanisms will
propagate the route to the other devices.
An existing route may be effectively deleted by setting
the ipRouteType object to “invalid” for the entry to be
deleted. An existing route may be modified by changing
fields in the desired entry (indexed by ipRouteDest) of the
routing table. A new route may be added by specifying
values for a table entry for which the index
(“ipRouteDest”) does not already exist.
To add a route using an SNMP set, you must specify a
group of minimal objects. These variable bindings must
be contained in a single Protocol Data Unit (PDU). The
objects are described in more detail in the following
sections. The minimal set consists of:
•
ipRouteDest
•
ipRouteIfIndex
The following objects are defaulted if not specified in
the set PDU used to add a route.
•
ipRouteMetric1 – Defaulted to 1 hop.
•
ipRouteMetric2 – Defaulted to –1 for standalone
devices.
•
ipRouteType – Defaulted to indirect.
•
ipRouteMask – Defaulted as specified in the MIB
description.
The following objects are unused in the E1 DSU/CSU
and setting them will have no effect on the operation of
the IP implementation.
•
ipRouteMetric3, ipRouteMetric4, ipRouteMetric5 –
Defaulted to –1 as specified in the MIB.
•
ipRouteNextHop – Defaulted to 0.0.0.0.
The following read-only objects must not be specified
in the set PDU used to add a route.
•
ipRouteProto – Set to netmgmt(3) by software.
•
ipRouteAge – Defaulted to 999.
•
ipRouteInfo – Set to OBJECT IDENTIFIER {0, 0}
since it is unused.
IP Group – “ipRouteDest” Object
(ipRouteEntry 1)
The ipRouteDest object serves as the index to the
routing table. Since indexes for tables must be unique,
only one route per destination may appear in the table. To
ensure that no duplicate destinations appear in the routing
table, the ipRouteDest object of the ipRouteTable is
treated as described in RFC 1354 (IP Forwarding Table
MIB):
“The destination IP address of this route. An entry with
a value of 0.0.0.0 is considered a default route. This object
may not take a Multicast (Class D) address value. Any
assignment (implicit or otherwise) of an instance of this
object to a value x must be rejected if the bitwise
logical–AND of x with the value of the corresponding
instance of the ipForwardMask object is not equal to x.”
IP Group – “ipRouteIfIndex” Object
(ipRouteEntry 1)
When the routing table is displayed, the ipRouteIfIndex
object for some entries may have a value greater than
ifNumber. In these cases, the ipRouteIfIndex refers to a
proprietary interface which is not currently implemented
by the interface group of MIB II. Route entries with an
unrecognized ipRouteIfIndex value should not be deleted.
When setting this object via SNMP, the ipRouteIfIndex
value can only assume an appropriate value of ifIndex
defined for the particular device type.
IP Group – “ipRouteMetric2” Object
(ipRouteEntry 4)
For standalone devices, ipRouteMetric2 is not used and
contains –1.
When adding a route to the routing table using SNMP,
do not specify a value for ipRouteMetric2.
