EIGRP topology and offset-list

[Michael69]

Hi,

I'm trying to do some routing changes on EIGRP. I would like to set up a new preferred route via an offset-list. The off-set list works and the metric encreased for the the specific route entry, but the EIGRP topology does not change.

I would like to have the router 10.232.7.126 as preferred route for 10.230.16.0/24, there for I increased on the first step the metric on router 10.230.43.225 up to 115968. But the the topology doesn't changed and router 10.230.43.225 is still on the second positions. I assumed router 10.232.7.126 will come up on second position.

Topology before the offset-list was implemented:

Test-Router#sh ip eigrp topology 10.230.16.0 255.255.255.0
EIGRP-IPv4 Topology Entry for AS(65431)/ID(10.232.1.90) for 10.230.16.0/24
  State is Passive, Query origin flag is 1, 1 Successor(s), FD is 34048
  Descriptor Blocks:
  10.230.23.249 (GigabitEthernet2/1), from 10.230.23.249, Send flag is 0x0
      Composite metric is (34048/31488), route is Internal
      Vector metric:
        Minimum bandwidth is 100000 Kbit
        Total delay is 330 microseconds
        Reliability is 255/255
        Load is 55/255
        Minimum MTU is 1500
        Hop count is 5
  10.230.43.225 (GigabitEthernet2/2), from 10.230.43.225, Send flag is 0x0
      Composite metric is (36096/33536), route is Internal
      Vector metric:
        Minimum bandwidth is 100000 Kbit
        Total delay is 410 microseconds
        Reliability is 255/255
        Load is 17/255
        Minimum MTU is 1500
        Hop count is 4
  10.232.7.126 (Port-channel1), from 10.232.7.126, Send flag is 0x0
      Composite metric is (34304/34048), route is Internal
      Vector metric:
        Minimum bandwidth is 100000 Kbit
        Total delay is 340 microseconds
        Reliability is 255/255
        Load is 8/255
        Minimum MTU is 1500
        Hop count is 6

Topology after I've  implemented the offset-list for router 10.230.43.225:

Test-Router#sh ip eigrp topology 10.230.16.0 255.255.255.0
EIGRP-IPv4 Topology Entry for AS(65431)/ID(10.232.1.90) for 10.230.16.0/24
  State is Passive, Query origin flag is 1, 1 Successor(s), FD is 34048
  Descriptor Blocks:
  10.230.23.249 (GigabitEthernet2/1), from 10.230.23.249, Send flag is 0x0
      Composite metric is (34048/31488), route is Internal
      Vector metric:
        Minimum bandwidth is 100000 Kbit
        Total delay is 330 microseconds
        Reliability is 255/255
        Load is 55/255
        Minimum MTU is 1500
        Hop count is 5
  10.230.43.225 (GigabitEthernet2/2), from 10.230.43.225, Send flag is 0x0
      Composite metric is (115968/113408), route is Internal
      Vector metric:
        Minimum bandwidth is 100000 Kbit
        Total delay is 3535 microseconds
        Reliability is 255/255
        Load is 10/255
        Minimum MTU is 1500
        Hop count is 4
  10.232.7.126 (Port-channel1), from 10.232.7.126, Send flag is 0x0
      Composite metric is (34304/34048), route is Internal
      Vector metric:
        Minimum bandwidth is 100000 Kbit
        Total delay is 340 microseconds
        Reliability is 255/255
        Load is 8/255
        Minimum MTU is 1500
        Hop count is 6
 

Router 10.230.43.225 is still on the second place for a route to 10.230.16.0/24, can this someone please explain.

P 10.230.16.0/24, 1 successors, FD is 34048, serno 129594
        via 10.230.23.249 (34048/31488), GigabitEthernet2/1
        via 10.230.43.225 (115968/113408), GigabitEthernet2/2
        via 10.232.7.126 (34304/34048), Port-channel1

Thanks!

[Bekzod Fakhriddinov]

u must share ur diagram if u want us to understand . 

[Richard Burts]

I believe that there is some conceptual misunderstanding about the topology and how it is represented in the command output. The original post says this "but the EIGRP topology does not change". The order of the list does not change but the topology did change. There seems to be an assumption that the order of the list in the output reflects the order of preference for the route. But that is not the case. Of the 3 alternative routes the route through 10.230.43.225 already has the worst metric and would be the third alternative to be used, but has second place in the list. The offset list made the metric even worse but does not change the order of the list.

Note that if the original poster wants the route through 10.232.7.126 to become the preferred route then an off set list need to be applied to the current preferred route through 0.230.23.249. It appears that an offset list may not be needed for the route through 10.230.43.225 since its metric is already worse than the other alternatives.

HTH

Rick