Description

The device has ISIS adjacency up but not route in the routing table. The ISIS database was correctly updated, all the routes were there in the database.

Symptoms

All the ISIS adjacency are up , but no ISIS route is routing table. ISIS database correctly populated.
 

Solution

This is expected behavior and is seen when the device is costed out with the highest ISIS metric  16777215.

  
regress@PE1_re> show route protocol isis   << - lab device no ISIS routes
 
inet.0: 12 destinations, 12 routes (12 active, 0 holddown, 0 hidden)
 
inet.3: 1 destinations, 1 routes (1 active, 0 holddown, 0 hidden)
 
CE1.inet.0: 8 destinations, 9 routes (3 active, 0 holddown, 6 hidden)
 
iso.0: 2 destinations, 2 routes (2 active, 0 holddown, 0 hidden)
 
mpls.0: 11 destinations, 11 routes (11 active, 0 holddown, 0 hidden)
 
bgp.l3vpn.0: 6 destinations, 6 routes (0 active, 0 holddown, 6 hidden)
 
inet6.0: 3 destinations, 3 routes (3 active, 0 holddown, 0 hidden)
 
CE1.inet6.0: 1 destinations, 1 routes (1 active, 0 holddown, 0 hidden)
 
regress@PE1_re> 
 
regress@PE1_re> show isis adjacency 
Interface       System     L State     Hold (secs) SNPA
ge-0/0/1.0      P1_re     2 Up          23
ge-0/0/2.0      PE2_re     2 Up          20
 
regress@PE2_re> show configuration protocols isis | display set 
set protocols isis interface ge-0/0/0.0 level 2 metric 16777215. << -- link towards PE1
 
regress@P1_re> show configuration protocols isis | display set  
set protocols isis interface ge-0/0/0.0 level 2 metric 16777215. << -- link towards PE1
 
regress@PE1_re> show isis database
IS-IS level 1 link-state database:
  0 LSPs
 
IS-IS level 2 link-state database:
LSP ID                      Sequence Checksum Lifetime Attributes
PE1_re.00-00                   0x979   0x35e1     1034 L1 L2
PE2_re.00-00                   0x8ed   0xbc8e     1005 L1 L2 Overload
P2_re.00-00                    0x8cf   0x725e      634 L1 L2
P1_re.00-00                    0x948   0x59ec     1059 L1 L2
 
regress@PE1_re> show isis database P1_re.00-00 extensive
IS-IS level 1 link-state database:
 
IS-IS level 2 link-state database:
 
P1_re.00-00 Sequence: 0x948, Checksum: 0x59ec, Lifetime: 1032 secs
   IS neighbor: PE1_re.00                     Metric: 16777215
   IS neighbor: P2_re.00                      Metric:      100
     Two-way fragment: P2_re.00-00, Two-way first fragment: P2_re.00-00
   IS neighbor: PE3_re.00                     Metric:      100
     Two-way fragment: PE3_re.00-00, Two-way first fragment: PE3_re.00-00
   IP prefix: 11.11.11.0/30                   Metric: 16777215 Internal Up
   IP prefix: 11.11.11.11/32                  Metric:        0 Internal Up
   IP prefix: 13.13.13.0/30                   Metric:      100 Internal Up
   IP prefix: 102.102.102.0/30                Metric:      100 Internal Up
   V6 prefix: abcd::128:52:134:199/128        Metric:        0 Internal Up
 
  Header: LSP ID: P1_re.00-00, Length: 434 bytes
    Allocated length: 434 bytes, Router ID: 11.11.11.11
    Remaining lifetime: 1032 secs, Level: 2, Interface: 444
    Estimated free bytes: 0, Actual free bytes: 0
    Aging timer expires in: 1032 secs

 

Modification History

2024-09-02 : Article Created