33.6. OSPF External Routes filter table

The table of OSPF External Routes contains information about filtering rules for routes which are external to the OSPF domain and which could be imported into the OSPF domain.

This table is used only when this router is declared as ASBR (ASBR:YES).

The table of OSPF External Routes is used as follows:

  1. An empty table is a “default accept” table.

  2. A table with only “ignore” records is still a “default accept” table.

  3. A table with at least one “accept” record for a protocol becomes a “default ignore” for that protocol.

In the first case, the filtering is possible only “by protocol” (through the parameters LOCAL, STATIC and RIP).

In the second case, routes are ignored.

In the third case, all the routes for the protocol having at least one “accept” record are ignored, except those explicitly accepted.

Commands for managing the table of OSPF External Routes are the following:

33.6.1. D OSPF EXTERNAL (Display OSPF External Routes filter)

This command shows the content of the Table of OSPF External Routes.

[16:45:23] ABILIS_CPX:d ospf external

-----------------------------------------------------
EXTERNAL:            PROT:   ACTION:   METRIC:  TYPE:
-----------------------------------------------------
192.168.006.002/32   RIP     ACCEPT          5      1
192.168.006.000/24   LOCAL   IGNORE          1      1
010.000.000.000/08   STATIC  ACCEPT         10      1
000.000.000.000/00   ANY     IGNORE          *      1
-----------------------------------------------------

Meaning of the parameters:

EXTERNAL

It specifies the external IP network that can be imported (or not) into OSPF resource. External network IP address and mask in Slash Notation [0.0.0.0, 1-126.x.x.x, 127.0.0.1, 128-223.x.x.x]/[0..32].

PROT

This parameter defines a routing protocol for which this filter will be applied [ANY, LOCAL, STATIC, RIP];

ACTION

This parameter indicates if the selected network can be accepted or ignored by OSPF resource [IGNORE: do not distribute this IP addresses into OSPF; ACCEPT: distribute this IP addresses into OSPF]. This means that all the routing present in the IP Routings table which matches will be imported to OSPF table in case that is set to ACCEPT (and then will be used also specified metric), and will be not imported in case that it is set to IGNORE.

METRIC

This parameter sets the metric value that will be used for redistribution routes, of LOCAL, STATIC or RIP type, imported from the IP Routings table into OSPF. The value * stands for “use default metric”.

TYPE

Type of external route [1, 2].

The allowed syntax of the command is:

  • d ospf external: it shows the table.

  • d ospf external:x.x.x.x/yy PROT:val: it shows the specified entry.

33.6.2. A OSPF EXTERNAL (Add OSPF External Routes filter)

It adds a new entry to the Table of OSPF External Routes.

The syntax of the command is:

a OSPF external:x.x.x.x/yy prot:val action:val [metric:val]

Example: add a rule to accept the OSPF packets for the net 192.168.5.0/24 (static routing) and assign to it the exporting metric value 5.

[16:19:36] ABILIS_CPX:a ospf external:192.168.5.0/24 prot:static action:accept metric:5

COMMAND EXECUTED

[16:54:47] ABILIS_CPX:d ospf external

- Not Saved (SAVE CONF), Not Refreshed (INIT) ---------------------------------
-----------------------------------------------------
EXTERNAL:            PROT:   ACTION:   METRIC:  TYPE:
-----------------------------------------------------
192.168.006.002/32   RIP     ACCEPT          5      1
192.168.005.000/24   STATIC  ACCEPT          5      1
192.168.006.000/24   LOCAL   IGNORE          1      1
010.000.000.000/08   STATIC  ACCEPT         10      1
000.000.000.000/00   ANY     IGNORE          *      1
-----------------------------------------------------

33.6.3. C OSPF EXTERNAL (Clear OSPF External Routes filter)

It deletes the OSPF external route entry identified by the specified mandatory parameters.

The syntax of the command is:

c OSPF external:x.x.x.x/yy prot:val

Example: clear the entry added in the previous paragraph.

[16:54:47] ABILIS_CPX:d ospf external

- Not Saved (SAVE CONF), Not Refreshed (INIT) ---------------------------------
-----------------------------------------------------
EXTERNAL:            PROT:   ACTION:   METRIC:  TYPE:
-----------------------------------------------------
192.168.006.002/32   RIP     ACCEPT          5      1
192.168.005.000/24   STATIC  ACCEPT          5      1
192.168.006.000/24   LOCAL   IGNORE          1      1
010.000.000.000/08   STATIC  ACCEPT         10      1
000.000.000.000/00   ANY     IGNORE          *      1
-----------------------------------------------------

[16:55:02] ABILIS_CPX:c ospf external:192.168.5.0/24 prot:static                       

COMMAND EXECUTED 

[16:56:11] ABILIS_CPX:d ospf external                            

- Not Saved (SAVE CONF), Not Refreshed (INIT) ---------------------------------
-----------------------------------------------------
EXTERNAL:            PROT:   ACTION:   METRIC:  TYPE:
-----------------------------------------------------
192.168.006.002/32   RIP     ACCEPT          5      1
192.168.006.000/24   LOCAL   IGNORE          1      1
010.000.000.000/08   STATIC  ACCEPT         10      1
000.000.000.000/00   ANY     IGNORE          *      1
-----------------------------------------------------

33.6.4. S OSPF EXTERNAL (Set OSPF External Routes filter)

It sets new values of the parameters of the OSPF external route entry.

The syntax of the command is:

s OSPF external:x.x.x.x/yy prot:val par:val [par:val...]

Example: change the metric value to an already existing entry.

[16:57:24] ABILIS_CPX:d ospf external

- Not Saved (SAVE CONF), Not Refreshed (INIT) ---------------------------------
-----------------------------------------------------
EXTERNAL:            PROT:   ACTION:   METRIC:  TYPE:
-----------------------------------------------------
192.168.006.002/32   RIP     ACCEPT          5      1
192.168.005.000/24   STATIC  ACCEPT          5      1
192.168.006.000/24   LOCAL   IGNORE          1      1
010.000.000.000/08   STATIC  ACCEPT         10      1
000.000.000.000/00   ANY     IGNORE          *      1
-----------------------------------------------------

[16:57:30] ABILIS_CPX:s ospf external:192.168.5.0/24 prot:static action:accept metric:3

COMMAND EXECUTED 

[16:57:35] ABILIS_CPX:d ospf external                                                  

- Not Saved (SAVE CONF), Not Refreshed (INIT) ---------------------------------
-----------------------------------------------------
EXTERNAL:            PROT:   ACTION:   METRIC:  TYPE:
-----------------------------------------------------
192.168.006.002/32   RIP     ACCEPT          5      1
192.168.005.000/24   STATIC  ACCEPT          3      1
192.168.006.000/24   LOCAL   IGNORE          1      1
010.000.000.000/08   STATIC  ACCEPT         10      1
000.000.000.000/00   ANY     IGNORE          *      1
-----------------------------------------------------