EIGRP Topology output help!

[Ricky S]

Hi everyone, here is an output from my router which has 2 vpn tunnels going to separate routers. Why does it say 1 Successor? Shouldn't it be 2 Sucessors?

#sh ip eigrp top 172.18.24.0/24

EIGRP-IPv4 Topology Entry for AS(1)/ID(1.1.1.203) for 172.18.24.0/24

  State is Passive, Query origin flag is 1, 1 Successor(s), FD is 1331456

  Descriptor Blocks:

  10.10.200.24 (Tunnel0), from 10.10.200.1, Send flag is 0x0

      Composite metric is (1331456/1305088), route is Internal

      Vector metric:

        Minimum bandwidth is 100000 Kbit

        Total delay is 51010 microseconds

        Reliability is 255/255

        Load is 12/255

        Minimum MTU is 1400

        Hop count is 2

  10.10.201.24 (Tunnel1), from 10.10.201.1, Send flag is 0x0

      Composite metric is (1561856/1305088), route is Internal

      Vector metric:

        Minimum bandwidth is 100000 Kbit

        Total delay is 60010 microseconds

        Reliability is 255/255

        Load is 1/255

        Minimum MTU is 1400

        Hop count is 2

[John Blakley · Accepted solution]

Ricky,

You'll only have 1 successor which will be in the routing table (unless metrics match exactly, in which case you can have multiple routes in the routing table). The other route is a feasible successor. If you lose the connection that leads to this route, EIGRP can fail over to the feasible successor without having to query neighbors.

HTH,

John

[Ricky S]

Thanks

[Ricky S]

Hi John, I have another question that is related. If you see the output below, Descriptor Block for 10.10.200.155 has ECMP mode set to Advertise by default. Whereas for 10.10.201.155, it's set differently. What is ECMP mode? I am having a weird random and sporadic issue on my network which I am trying to zero in on where 2 routers know routes to one another but can't ping each other. Whereas I can ping both of them from everywhere else in the network and vice versa. There are no ACLs involved in my internal network.

EIGRP-IPv4 Topology Entry for AS(1)/ID(192.168.155.150) for 172.18.155.0/24

State is Passive, Query origin flag is 1, 1 Successor(s), FD is 1620480

Descriptor Blocks:

10.10.200.155 (Tunnel0), from 10.10.200.1, Send flag is 0x0

Composite metric is (1620480/1308160), route is Internal

Vector metric:

Minimum bandwidth is 8192 Kbit

Total delay is 51100 microseconds

Reliability is 255/255

Load is 67/255

Minimum MTU is 1400

Hop count is 2

ECMP Mode: Advertise by default

10.10.201.155 (Tunnel1), from 10.10.201.1, Send flag is 0x0

Composite metric is (1850880/1308160), route is Internal

Vector metric:

Minimum bandwidth is 8192 Kbit

Total delay is 60100 microseconds

Reliability is 255/255

Load is 1/255

Minimum MTU is 1400

Hop count is 2

ECMP Mode: Advertise out Tunnel1

[John Blakley]

Ricky,

ECMP is equal cost multipath routing and basically means that it will support multiple paths in the routing table. If I remember right in a previous post, didn't you want to support only 1 route in the routing table? I think the fix was to set "maximum-paths" to 1. I assume that ECMP is "advertise by default" because it's the only route in the routing table. If you had both routes, it may say advertise by default for both. I have to lab this one up and get back to you....

HTH,

John

[John Blakley]

Ricky,

Unfortunately, I can't verify this. The version of IOS that I run doesn't have ECMP supported in the topology listing, so I can't tell you for sure what manipulates it. Maybe someone else would be able to help.

John

[Ricky S]

Hi John,

Yes you are correct. I am using maximum-path 1 for all my EIGRP instances. I decreased the delay on Tunnel0 to make it the preffered route for all my traffic. Tunnel 1 is used for backup. I am not sure why ECMP mode for Tunnel1 is saying Advertise out Tunnel1.

No problem Thanks for trying anyways

[John Blakley]

Ricky,

I found this, and surprisingly enough I was very close

From this link:

http://www.cisco.com/en/US/docs/ios-xml/ios/mtr/command/mtr-s1.html#GUID-71A35F96-D4F8-4875-8BD9-90CF1AE4E22E

The following sample output from the              show ip eigrp topology                  prefix command displays ECMP mode information when the              no ip next-hop-self command is configured without the              no-ecmp-mode  option in an EIGRP topology. ECMP mode provides information about the  path that is being advertised. If there is more than one successor, the  top most path will be advertised as the default path over all  interfaces, and "ECMP Mode: Advertise by default" will be displayed in  the output. If any path other than the default path is advertised, "ECMP  Mode: Advertise out " will be displayed.

Device# show ip eigrp topology 192.168.10.0/24

EIGRP-IPv4 Topology Entry for AS(1)/ID(20.20.100.100) for 192.168.10.0/24
State is Passive, Query origin flag is 1, 2 Successor(s), FD is 284160
  Descriptor Blocks:
  10.100.1.0 (Tunnel0), from 10.100.0.1, Send flag is 0x0
      Composite metric is (284160/281600), route is Internal
      Vector metric:
        Minimum bandwidth is 10000 Kbit
        Total delay is 1100 microseconds
        Reliability is 255/255
        Load is ½55
        Minimum MTU is 1400
        Hop count is 1
        Originating router is 10.10.1.1
        ECMP Mode: Advertise by default
        10.100.0.2 (Tunnel1), from 10.100.0.2, Send flag is 0X0
     Composite metric is (284160/281600), route is Internal
     Vector metric:
     Minimum bandwidth is 10000 Kbit
     Total delay is 1100 microseconds
     Reliability is 255/255
     Load is ½55
     Minimum MTU is 1400
     Hop count is 1
     Originating router is 10.10.2.2
        ECMP Mode: Advertise out Tunnel1

[Ricky S]

Thanks John for the explaination. I am still wondering whether using maximum-paths 1 command in EIGRP in a dual hub dual-dmvpn cloud scenario is beneficial. I am using Tunnel0 to Hub1 as the primary link for all sites and Tunnel1 to Hub2 aS backup for all sites. Both tunnels are on separate subnets. Way I am accomplishing this is by adjusting the delay on both interfaces. Since delay on Tunnel0 is always less than tunnel1, sites will always pick tunnel0 as the main link. Having maximum-paths 1 may not serve any purpose at this point unless I had 2 headend-hubs on the same inner DMVPN network.