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Ping fails Because the Number of Routes on the S65 Exceeds the Specification and Cannot Be Delivered to the FIB Table

Publication Date:  2013-01-07 Views:  30 Downloads:  0
Issue Description

An S6506R V3.3037 is deployed at a site. When the new services are tested, a user cannot ping the gateway on the S6506R. When the S6506R is logged in to and tested, the S6506R cannot ping its own interface address. The interface IP address with a 30-bit mask is configured.

Handling Process

If a large number of routes with short masks are learned on the S6506R, such as small network segment routes with 30-bit masks or 29-bit masks, some routes may not be reachable. The procedures for diagnosis are as follows:

You can find the route using the display ip route command. But you cannot find the FIB table to which this route belongs using the display fib command. The two commands helps confirm that the routing entries are not delivered from the software plane to the FIB table, which is possibly because that the number of routes on the S6506R exceeds the specification.

Run the l3drv route 0 command in the diagnostic view. The command output is as follows. This switch has 10192 route item and 10048 ecmp route item.

AllCount 501858893, AddCount 497229091,AddECount 495060607,DelCount 4629802,DelECount 0

Unit 0, Total Number of DEFIP entries: 65536

Free LPM blocks: 0, Free LPM entries: 0

Indicates that the number of remaining hardware routing entries is 0.

Check the route entries and find that the S6506R has learned a large number of routes with short masks, such as small network segment routes with 30-bit masks and 29-bit masks.

Root Cause

The routes exceed the specification, causing the routes to fail to be delivered to the FIB table.

Solution

Solution 1: Converge routes on the upstream device to prevent the S6506R from generating massive discrete small network segment routes.

Solution 2: Configure route filtering on the S6506R to enable the S6506R to learn the default routes and some small network segment routes. This way helps reduce the number of small network segment routes.

END