When the default configuration in MPC7-MRATE in an MX series router is modified under the chassis stanza to set up 40g/100g speeds and the Modular Port Concentrator (MPC) is not restarted, the " fpcx   ifd xxx; does not exist " syslog message is logged.

If this configuration change is followed with a graceful Routing Engine switchover (GRES), interface inconsistency and other kernel issues may also be observed when the new Routing Engine takes over.

This article explains why this happens and what should be done to resolve the error, and avoid any kernel and interface inconsistency issues.

The following logs are seen continuously:

Oct 23 10:28:00.919 2018  Juniper-Mx960 fpc5   ifd 294; does not exist
Oct 23 10:28:11.448 2018  Juniper-Mx960 fpc5   ifd 295; does not exist
Oct 23 10:28:21.955 2018  Juniper-Mx960 fpc5   ifd 296; does not exist
Oct 23 10:28:32.506 2018  Juniper-Mx960 fpc5   ifd 297; does not exist
Oct 23 10:28:43.080 2018  Juniper-Mx960 fpc5   ifd 298; does not exist
Oct 23 10:28:53.598 2018  Juniper-Mx960 fpc5   ifd 299; does not exist

MPC7-MRATE comes with all the interfaces in the xe-X/Y/Z format by default. After modifying the chassis commands to select 40g/100g speeds, the Flexible PIC Concentrator (FPC) needs a restart. When the FPC is restarted, the xe-X/Y/Z interface is replaced with the et-X/Y/Z interface.

Failing to restart the FPC after changing configuration and following the modification with a primary Routing Engine switchover, however, will lead to missing interface indexes and system inconsistency, as shown in the following output:

Identifying the interfaces related to the above indexes ( show interfaces ):

Physical interface: et-5/0/0, Enabled, Physical link is Down
  Interface index: 294, SNMP ifIndex: 809, Generation: 297

Physical interface: et-5/0/2, Enabled, Physical link is Down
  Interface index: 295, SNMP ifIndex: 810, Generation: 298

Physical interface: et-5/0/5, Enabled, Physical link is Down
  Interface index: 296, SNMP ifIndex: 811, Generation: 299

Physical interface: et-5/1/0, Enabled, Physical link is Down
  Interface index: 297, SNMP ifIndex: 812, Generation: 300

Physical interface: et-5/1/2, Enabled, Physical link is Down
  Interface index: 298, SNMP ifIndex: 813, Generation: 301

Physical interface: et-5/1/5, Enabled, Physical link is Down
  Interface index: 299, SNMP ifIndex: 814, Generation: 302

When the chassis configuration for FPC5 is modified as follows:

chassis {
    fpc 5 {
        pic 0 {
            port 0 {
                speed 40g;
            }
            port 2 {
                speed 100g;
            }
            port 5 {
                speed 100g;
            }
        }
        pic 1 {
            port 0 {
                speed 40g;
            }
            port 2 {
                speed 100g;
            }
            port 5 {
                speed 100g;
            }
        }
    }
    network-services enhanced-ip;
}

And the MPC is not restarted, observe the interface inconsistency in the output:

root@Juniper-Mx960> show system queues no-forwarding | match -5/0/0

lc-5/0/0                        0            0        0        0        0
pfh-5/0/0                       0            0        0        0        0
pfe-5/0/0                       0            0        0        0        0
xe-5/0/0:0                      0      1250000        0     4166        0
xe-5/0/0:1                      0      1250000        0     4166        0
xe-5/0/0:2                      0      1250000        0     4166        0
xe-5/0/0:3                      0      1250000        0     4166        0
et-5/0/0                        0      1250000        0     4166        0

As seen above, 5/0/0 has both " xe " and " et " interfaces, which is wrong. The same will occur in the other reported interfaces: 5/0/2 , 5/0/5 , 5/1/0 , 5/1/2 , and 5/1/5 .

MPC7-MRATE will require a restart to avoid possible kernel inconsistencies and to eliminate the syslog message.