eigrp....this is a "no brain-teaser"

Hi there

 

Guys just a simple observation, with eigrp ..."redistr conn or static can be applied without the metric parameters and will still be adverticed to other eigrp peers.....

 

I was unsure about this due to some of the SG's I've seen the metric included...but without the metric parameters It was advertised!

 

any comments anyone like to add?

 

Comments

  • However if you do a redistribute ospf or rip etc into eigrp then it won't be announced without using the metric. I always try to set a metric when doing redistribution that will show me that it was redistributed. If I'm redistributing into RIP I set a higher metric so that I will see that it was redistributed.

  • Hi JJ,

    Good question again!.

    See this example:

    I have native EIGRP route and redistributed route from R6:

    6.6.6.6/32 is advertised into EIGRP and 66.66.66.66 is redistributed connected network:

    1. R6(config-router)#do show run | section router eigrp
    router eigrp 100
     redistribute connected route-map lo66
     network 6.6.6.6 0.0.0.0
     network 56.56.56.6 0.0.0.0
     no auto-summary

    R5#show ip eigrp topology 6.6.6.6/32
    IP-EIGRP (AS 100): Topology entry for 6.6.6.6/32
      State is Passive, Query origin flag is 1, 1 Successor(s), FD is 156160
      Routing Descriptor Blocks:
      56.56.56.6 (FastEthernet0/0), from 56.56.56.6, Send flag is 0x0
          Composite metric is (156160/128256), Route is Internal
          Vector metric:
            Minimum bandwidth is 100000 Kbit
            Total delay is 5100 microseconds
            Reliability is 255/255
            Load is 1/255
            Minimum MTU is 1500
            Hop count is 1
    R5#show ip eigrp topology 66.66.66.66/32
    IP-EIGRP (AS 100): Topology entry for 66.66.66.66/32
      State is Passive, Query origin flag is 1, 1 Successor(s), FD is 156160
      Routing Descriptor Blocks:
      56.56.56.6 (FastEthernet0/0), from 56.56.56.6, Send flag is 0x0
          Composite metric is (156160/128256), Route is External
          Vector metric:
            Minimum bandwidth is 100000 Kbit
            Total delay is 5100 microseconds
            Reliability is 255/255
            Load is 1/255
            Minimum MTU is 1500
            Hop count is 1
          External data:
            Originating router is 6.6.6.6
            AS number of route is 0
            External protocol is Connected, external metric is 0
            Administrator tag is 0 (0x00000000)

    Now if you look the composite metric of 6.6.6.6/32 and 66.66.66.66/32 is same, while redistributing connected or static route, you don't need to specify metric because EIGRP treats connected/static redistributed routes like as locally advertising network into EIGRP (how EIGRP treats network x.x.x.x for metric?).

    Now you have option to specify metric as well, if you specify metric EIGRP starts calculate composite metric based on that.

    2. R6(config-router)#do show run | section router eigrp
    router eigrp 100
     redistribute connected metric 1 1 1 1 1 route-map lo66
     network 6.6.6.6 0.0.0.0
     network 56.56.56.6 0.0.0.0
     no auto-summary
    R5#show ip eigrp topology 66.66.66.66/32
    IP-EIGRP (AS 100): Topology entry for 66.66.66.66/32
      State is Passive, Query origin flag is 1, 1 Successor(s), FD is 2560002816
      Routing Descriptor Blocks:
      56.56.56.6 (FastEthernet0/0), from 56.56.56.6, Send flag is 0x0
          Composite metric is (2560002816/2560000256), Route is External
          Vector metric:
            Minimum bandwidth is 1 Kbit
            Total delay is 110 microseconds
            Reliability is 1/255
            Load is 1/255
            Minimum MTU is 1
            Hop count is 1
          External data:
            Originating router is 6.6.6.6
            AS number of route is 0
            External protocol is Connected, external metric is 0
            Administrator tag is 0 (0x00000000)

    I hope this clears little bit:)

    HAPPY STUDY

    [:D]

  • yes...good one guys! yes agreed that with other IGP redistributing in we need to set metric!

     

    Thanks for sharing!

  • Guys just a simple observation, with eigrp ..."redistr conn or static can be applied without the metric parameters and will still be adverticed to other eigrp peers.....

     

     


    When we redistribute between EIGRP, we also doesn't need to specify metric.

  • Back when I was studying for CCNA/CCDA/CCNP, IGRP was a routing protocol covered by the exams. (2002/2003)

    You can redistribute between IGRP and EIGRP, or between EIGRP domains, and the metrics were automatic - IGRP metric * 256 = EIGRP metric (if I remember correctly), and of course EIGRP metrics from one domain transferred straight across to another EIGRP domain.

    Even if redistributed static/connected routes are sent to EIGRP peers without specifying the metric, it would be a good idea to configure a metric whenever redistributing into RIP or EIGRP. RIP will see the lack of metric as infinite/16 hops, and EIGRP may have unexpected results when the metric is not specified. You can also configure a default metric for these protocols to satisfy this requirement.

    An exception is where MP-BGP carries the EIGRP or RIP metric between sites.

  • Hi Alex/Darrel.... thanks for sharing....yes also have it like that.....

    was an interesting behaviour I saw.....

  • Hi JJ,

    We forgot to talk about redistribution from BGP to EIGRP and vice-versa, when you redistribute BGP into EIGRP, you don't need to specify metric:

    This is my topology:

    R1-EIGRP-R2-BGP-R3

    R2(config-router)#do show run | section router eigrp|bgp
    router eigrp 100
     redistribute bgp 2
     network 12.12.12.2 0.0.0.0
     no auto-summary
    router bgp 2
     no synchronization
     bgp log-neighbor-changes
     network 2.2.2.2 mask 255.255.255.255
     redistribute eigrp 100
     neighbor 23.23.23.3 remote-as 3
     no auto-summary
    R3(config-router)#do show ip route
    <removed>
    Gateway of last resort is not set

         1.0.0.0/32 is subnetted, 1 subnets
    B       1.1.1.1 [20/156160] via 23.23.23.2, 00:00:31
         3.0.0.0/32 is subnetted, 1 subnets
    C       3.3.3.3 is directly connected, Loopback0
         23.0.0.0/24 is subnetted, 1 subnets
    C       23.23.23.0 is directly connected, FastEthernet0/0
         12.0.0.0/24 is subnetted, 1 subnets
    B       12.12.12.0 [20/0] via 23.23.23.2, 00:08:15
    R3(config-router)#do ping 1.1.1.1 so lo0

    Type escape sequence to abort.
    Sending 5, 100-byte ICMP Echos to 1.1.1.1, timeout is 2 seconds:
    Packet sent with a source address of 3.3.3.3
    !!!!!
    Success rate is 100 percent (5/5), round-trip min/avg/max = 64/104/160 ms
    !
    R1(config-router)#do show ip route
    <removed>

        1.0.0.0/32 is subnetted, 1 subnets
    C       1.1.1.1 is directly connected, Loopback0
         3.0.0.0/32 is subnetted, 1 subnets
    D EX    3.3.3.3 [170/2560002816] via 12.12.12.2, 00:01:40, FastEthernet0/0
         12.0.0.0/24 is subnetted, 1 subnets
    C       12.12.12.0 is directly connected, FastEthernet0/0
    R1(config-router)#do ping 3.3.3.3

    Type escape sequence to abort.
    Sending 5, 100-byte ICMP Echos to 3.3.3.3, timeout is 2 seconds:
    !!!!!
    Success rate is 100 percent (5/5), round-trip min/avg/max = 48/76/112 ms

    HAPPY STUDY

    [:D]

  • We forgot to talk about redistribution from BGP to EIGRP and vice-versa, when you redistribute BGP into EIGRP, you don't need to specify metric:

     

     


    Good to know!

     

    thanks for sharing NNN

  • Hi,

      Theory says, when you redistribute an IGP/static/connected into DV protocols (like RIP/EIGRP), metric is infinite, unless seed metric or specific metric is advertised. This was the behavior for a while in IOS'es. Since some version of IOS 12.4 things have changed and still are presents in 12.4T and 15.x: connected and static routes redistributed in EIGRP are advertised with a metric by default, even if seed metric or specific metric is not configured and this makes all sense in the world: for RIP, RIP can see that networks are directly connected or one hop away and just inject the prefix in the RIp databasw with repsective metric/hop count; for EIGRP, EIGRP can see the exit interface for the connected or static prefix and collect the sum of delay and lowest bw (actually the delay and bw in this case),and use these values when prefixes get injected in the topology table.

     However, as other said, it is always recommended to still sue specific or seed metric on redistribution.

    Good luck with your studies!

  • However, as other said, it is always recommended to still sue specific or seed metric on redistribution.

    This makes common habit to redistribute and good for IGP traffic Engineering!

    HAPPY STUDY

    [:D]

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