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Because the UNR Route Is Imported Only to IS-IS Level 2 for the ME60 by Default, Users Fail to Access the Internet Without a Return Route

Publication Date:  2012-07-27 Views:  69 Downloads:  0
Issue Description

Networking: Internet--Router--ME60--DSLAM--Modem--Clients

Version: ME60V100R005 and later versions

Symptom: The IS-IS routing protocol runs between the ME60 and the upstream router. The IS-IS level for the ME60 is 1�2. Users can log in but cannot access the network. The Internet network cannot be pinged. Check the ME60 configuration. Ensure that the import unr command is used in the IS-IS view.
Alarm Information
Null
Handling Process

1、Users can log in. It indicates that the ME60 communicates with the AAA servers such as RADIUS servers properly. The device works properly. Routing is probably the problem.

2、Log in to the client. Use the tracert command to trace the route. Only the ME60 can be traced. The next hop cannot be traced.

3、The UNR route of users can be seen on the ME60.

display ip routing-table 2x.x.186.100

Route Flags: R - relay, D - download to fib

------------------------------------------------------------------------------

Routing Table : Public

Summary Count : 1

Destination/Mask    Proto  Pre  Cost     Flags NextHop         Interface

2x.x.186.100/32    Unr    61   0        D  2x.x.186.100   InGigabitEthenet1/0/0.1

The upstream device does not include a route to the corresponding user network segment. This indicates that the upstream device does not learn the route of the user network segment. The import unr command, however, is used in the configuration.

isis 1

network-entity 00.0005.0000.0000.0002.00

import-route unr

#

4、On the ME60, check IS-IS LSDB. The user network segment route exists only in IS-IS level 2.

Information for ISIS(1)

                        --------------------------------

                     Level-1 Link State Database

LSPID         Seq Num      Checksum      Holdtime      Length  ATT/P/OL

-------------------------------------------------------------------------------

0000.0000.0002.00-00* 0x00000002   0x4921     481           35      0/0/0

SOURCE       0000.0000.0002.00

AREA ADDR    00.0005

*(In TLV)-Leaking Route, *(By LSPID)-Self LSP, +-Self LSP(Extended),

ATT-Attached, P-Partition, OL-Overload

//The UNR route is not imported to IS-IS level 1.

                    Level-2 Link State Database

LSPID         Seq Num      Checksum      Holdtime      Length  ATT/P/OL

------------------------------------------------------------------------------

0000.0000.0002.00-00* 0x00000003       0x4722    480          35      0/0/0

SOURCE       0000.0000.0002.00

AREA ADDR    00.0005

0000.0000.0002.00-01* 0x00000003   0x99bf        477           463     0/0/0   

SOURCE       0000.0000.0002.00

IP-External  59.x.x.0     255.255.252.0    COST: 64

IP-External  2x.x.186.0    255.255.252.0    COST: 64

//The UNR route of the user network segment is not imported to IS-IS level 2.

IP-External  59.x.x.64    255.255.255.224  COST: 64

Check the configuration. By default, the ME60 is configured to run IS-IS level 1�2. The upstream device runs IS-IS level 1. Therefore, the route information about the user network segment is not published to the upstream route.

5、After the import unr level-1 command is used on the ME60, the upstream route can learn the route of the user network segment. Users can access the Internet then.

#

isis 1

network-entity 00.0005.0000.0000.0002.00

import-route unr level-1
Root Cause
By default, the import unr command on the ME60 can import only the UNR route information to the IS-IS level-2 network. IS-IS level 1, however, runs between the ME60 and the upstream router. Therefore, the user route information is not published. In this case, users cannot log in. Other route such as interface routes, direct-connection routes, and static routes can be correctly imported to IS-IS level 1 and published. Therefore, users can log in.
Suggestions

Check the default configuration. When the import unr level-1-2 command is used on the ME60, the service can also be normal. Whether the route of the ME60 user network segment in the level-2 network is published depends on the service deployment. Typically, the upstream backbone zones of the ME60 are set to level 2.

This problem also occurs in the MA5200G VRP5.30.

END