RE: Set metric +/-<metric> on route-map for EIGRP

Tony,

Thanx for your response..
The problem is to arrive at the modified metric and make the route bless attractiveb, then I need to know the current Feasible distance of that route which make it difficult in a practical world if the FD is keep changing when I have multiple paths..

Rgds
Bala

From: Tony Singh [mailto:mothafungla_at_gmail.com]
Sent: Tuesday, January 07, 2014 5:34 PM
To: BALAKRISHNAN Balaji
Cc: ccielab_at_groupstudy.com; BALAKRISHNAN Balaji
Subject: Re: Set metric +/-<metric> on route-map for EIGRP

I believe the behaviour is down to only being able to increase the composite metric overall and not decrease it, decreasing a metric can lead lead to routing loops which IOS protects against similar to how an offset list is used.

The idea I guess is making a route more attractive then advertising out to its peers could cause peers to prefer this path whilst the peer modifying the route to a negative metric actually prefers the path via the same peer preferring him and vice versa, or similar along those lines, I think this also meets the EIGRP FC should Cisco have not seen it coming i.e If, for a destination, a neighbor router advertises a distance that is strictly lower than our feasible distance, then this neighbor lies on a loop free route to this destination -irrelevant but that's my understanding

In your case the modified "less attractive" route is then advertised to EIGRP peers, as you've seen but is seen as the genuine value in its own topology table as advertised by upstream peers.

In an offset-list you effectively change the delay value to affect the composite metric I think it's similar for your final solution but I would calculate according to the EIGRP algorithm to be sure.

I hope that helps.

--
BR
Tony
Sent from my iPad
On 7 Jan 2014, at 17:04, BALAKRISHNAN Balaji <Balaji.BALAKRISHNAN_at_swift.com<mailto:Balaji.BALAKRISHNAN_at_swift.com>> wrote:
Hi All,
While using route-map in the eigrp distribute-list, when I was configuring the metric, I stumble across a problemb&I wanted to offset the composite metric by a value so  I used the command bset metric  +1000000b but it did not have any impact.. Even if I use  bset metric  1000000b, it still did not have any impact.. Then I kept increasing the metric value and at certain value it start taking effect..  So,  I realized that  set metric command  will only work when the new metric is higher than the existing composite metric for that route and also  b+<metric>b  does not do any offset or add  to the current composite metric.. Can anyone explain this behaviour ?  Is there any way to implement the offset metric feature with route-map ?
## with No metric statement
R1# sh route-map FTAG-BA2MSG
route-map FTAG-BA2MSG, permit, sequence 10
 Match clauses:
   tag 193
 Set clauses:
 Policy routing matches: 0 packets, 0 bytes
R2#sh ip eigrp topology 172.24.225.0  255.255.255.0
EIGRP-IPv4 Topology Entry for AS(1)/ID(10.30.128.7) for 172.24.225.0/24
 State is Passive, Query origin flag is 1, 1 Successor(s), FD is 1028864
 Descriptor Blocks:
 10.25.128.10 (GigabitEthernet2/3), from 10.25.128.10, Send flag is 0x0
     Composite metric is (1028864/1028608), route is External
     Vector metric:
       Minimum bandwidth is 2500 Kbit
       Total delay is 190 microseconds
       Reliability is 255/255
       Load is 3/255
       Minimum MTU is 1500
       Hop count is 5
     External data:
       Originating router is 10.30.192.3
       AS number of route is 0
       External protocol is Connected, external metric is 0
       Administrator tag is 193 (0x000000C1)
## with metric statement set in R1
R1#sh route-map FTAG-BA2MSG
route-map FTAG-BA2MSG, permit, sequence 10
 Match clauses:
   tag 3
 Set clauses:
   metric 1000000      <-- metric set
 Policy routing matches: 0 packets, 0 bytes
R2#sh ip eigrp topology 172.24.225.0  255.255.255.0
EIGRP-IPv4 Topology Entry for AS(1)/ID(10.30.128.7) for 172.24.225.0/24
 State is Passive, Query origin flag is 1, 1 Successor(s), FD is 1028864
 Descriptor Blocks:
 10.25.128.10 (GigabitEthernet2/3), from 10.25.128.10, Send flag is 0x0
     Composite metric is (1028864/1028608), route is External      <--    No change in Composite metric in R2
     Vector metric:
       Minimum bandwidth is 2500 Kbit
       Total delay is 190 microseconds
       Reliability is 255/255
       Load is 3/255
       Minimum MTU is 1500
       Hop count is 5
     External data:
       Originating router is 10.30.192.3
       AS number of route is 0
       External protocol is Connected, external metric is 0
       Administrator tag is 193 (0x000000C1)
## with +metric statement set in R1
R1#sh route-map FTAG-BA2MSG
route-map FTAG-BA2MSG, permit, sequence 10
 Match clauses:
   tag 3
 Set clauses:
   metric +1000000  <-- + metric set
 Policy routing matches: 0 packets, 0 bytes
R2#sh ip eigrp topology 172.24.225.0  255.255.255.0
EIGRP-IPv4 Topology Entry for AS(1)/ID(10.30.128.7) for 172.24.225.0/24
 State is Passive, Query origin flag is 1, 1 Successor(s), FD is 1028864
 Descriptor Blocks:
 10.25.128.10 (GigabitEthernet2/3), from 10.25.128.10, Send flag is 0x0   o    still No change in the composite metric. Still backup route is preferred
     Composite metric is (1028864/1028608), route is External  <--    No change in Composite metric in R2
     Vector metric:
       Minimum bandwidth is 2500 Kbit
       Total delay is 190 microseconds
       Reliability is 255/255
       Load is 3/255
       Minimum MTU is 1500
       Hop count is 5
     External data:
       Originating router is 10.30.192.3
       AS number of route is 0
       External protocol is Connected, external metric is 0
       Administrator tag is 193 (0x000000C1)
## Increase the metric higher than the current composite metric for that route
R1#sh route-map FTAG-BA2MSG
route-map FTAG-BA2MSG, permit, sequence 10  o   Set the metric value to 1050000
 Match clauses:
   tag 3
 Set clauses:
   metric 1050000     <--  metric value higher than the current composite  metric
 Policy routing matches: 0 packets, 0 bytes
R2#sh ip eigrp topology 172.24.225.0  255.255.255.0
10.25.128.10 (GigabitEthernet2/3), from 10.25.128.10, Send flag is 0x0
     Composite metric is (268800256/268800000), route is External      <-  Change took effect
     Vector metric:
       Minimum bandwidth is 9 Kbit
       Total delay is 10 microseconds
       Reliability is 0/255
       Load is 3/255
       Minimum MTU is 241
       Hop count is 5
     External data:
       Originating router is 10.30.192.3
       AS number of route is 0
       External protocol is Connected, external metric is 0
       Administrator tag is 193 (0x000000C1)
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