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eigrp update missing route between switches?

Ryan Fisher
Level 1
Level 1

‎01-08-2011 11:02 AM - edited ‎03-06-2019 02:53 PM

So, I'm still learning eigrp and routing, so go easy on me!

This morning, I woke up to a bunch of emails that some remote systems were down.  After looking deeper into it, it appears that some routes aren't being exchanged between my core switch and my edge switch.

Topology:  two 6506 cores running vss, which connect to a 3750 edge switch, and run eigrp between them.  The 6506 is connected with a 3650 with hsrp for failover to the internet.

ED01-3750#sh ip route

Codes: C - connected, S - static, R - RIP, M - mobile, B - BGP

       D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area

       N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2

       E1 - OSPF external type 1, E2 - OSPF external type 2

       i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2

       ia - IS-IS inter area, * - candidate default, U - per-user static route

       o - ODR, P - periodic downloaded static route

Gateway of last resort is 10.201.1.2 to network 0.0.0.0

     172.16.0.0/24 is subnetted, 1 subnets

S       172.16.75.0 [1/0] via 10.74.193.1

     10.0.0.0/8 is variably subnetted, 52 subnets, 6 masks

D       10.13.5.0/24 [90/3072] via 10.200.253.2, 3w0d, Port-channel1

D       10.3.10.0/24 [90/3072] via 10.200.253.2, 3w0d, Port-channel1

D       10.200.199.0/24 [90/3072] via 10.200.253.2, 3w0d, Port-channel1

D       10.13.1.0/24 [90/3072] via 10.200.253.2, 3w0d, Port-channel1

D       10.3.15.0/24 [90/3072] via 10.200.253.2, 3w0d, Port-channel1

D       10.13.15.0/24 [90/3072] via 10.200.253.2, 3w0d, Port-channel1

D       10.3.1.0/24 [90/3072] via 10.200.253.2, 3w0d, Port-channel1

D       10.200.1.201/32 [90/1536] via 10.200.253.2, 3w0d, Port-channel1

D EX    10.0.0.0/8 [170/145800448] via 10.200.253.2, 03:44:21, Port-channel1

D       10.200.1.200/32 [90/1536] via 10.200.253.2, 3w0d, Port-channel1

D       10.1.0.0/16 [90/3072] via 10.200.253.2, 3w0d, Port-channel1

D       10.3.5.0/24 [90/3072] via 10.200.253.2, 3w0d, Port-channel1

D       10.13.10.0/24 [90/3072] via 10.200.253.2, 3w0d, Port-channel1

D       10.5.2.0/24 [90/3072] via 10.200.253.2, 3w0d, Port-channel1

D       10.5.1.0/24 [90/3072] via 10.200.253.2, 3w0d, Port-channel1

D       10.21.15.0/24 [90/3072] via 10.200.253.2, 3w0d, Port-channel1

D       10.20.15.0/24 [90/3072] via 10.200.253.2, 3w0d, Port-channel1

D       10.22.15.0/24 [90/3072] via 10.200.253.2, 3w0d, Port-channel1

D       10.19.10.0/24 [90/3072] via 10.200.253.2, 3w0d, Port-channel1

D       10.31.1.0/24 [90/3072] via 10.200.253.2, 3w0d, Port-channel1

D       10.20.10.0/24 [90/3072] via 10.200.253.2, 3w0d, Port-channel1

D       10.21.10.0/24 [90/3072] via 10.200.253.2, 3w0d, Port-channel1

D       10.22.10.0/24 [90/3072] via 10.200.253.2, 3w0d, Port-channel1

D       10.19.15.0/24 [90/3072] via 10.200.253.2, 3w0d, Port-channel1

D       10.19.1.0/24 [90/3072] via 10.200.253.2, 3w0d, Port-channel1

D       10.22.5.0/24 [90/3072] via 10.200.253.2, 3w0d, Port-channel1

D       10.31.15.0/24 [90/3072] via 10.200.253.2, 3w0d, Port-channel1

D       10.21.5.0/24 [90/3072] via 10.200.253.2, 3w0d, Port-channel1

D       10.20.5.0/24 [90/3072] via 10.200.253.2, 3w0d, Port-channel1

D       10.19.5.0/24 [90/3072] via 10.200.253.2, 3w0d, Port-channel1

D       10.22.1.0/24 [90/3072] via 10.200.253.2, 3w0d, Port-channel1

D       10.21.1.0/24 [90/3072] via 10.200.253.2, 3w0d, Port-channel1

D       10.31.10.0/24 [90/3072] via 10.200.253.2, 3w0d, Port-channel1

D       10.20.1.0/24 [90/3072] via 10.200.253.2, 3w0d, Port-channel1

D EX    10.32.0.0/16

           [170/256256] via 10.200.253.66, 03:45:24, GigabitEthernet2/0/14

C       10.200.253.0/30 is directly connected, Port-channel1

S       10.75.0.0/16 [1/0] via 10.200.253.74

D       10.100.10.0/24 [90/3072] via 10.200.253.2, 3w0d, Port-channel1

D       10.100.1.0/24 [90/3072] via 10.200.253.2, 3w0d, Port-channel1

C       10.200.253.72/29 is directly connected, GigabitEthernet2/0/21

C       10.200.253.64/29 is directly connected, GigabitEthernet2/0/14

S       10.74.193.0/24 [1/0] via 10.200.253.74

S       10.150.10.0/24 [1/0] via 10.201.1.2

D       10.200.2.0/24 [90/3072] via 10.200.253.2, 3w0d, Port-channel1

D       10.202.1.0/24 [90/3072] via 10.200.253.2, 3w0d, Port-channel1

D       10.200.3.0/24 [90/3072] via 10.200.253.2, 3w0d, Port-channel1

C       10.201.1.0/24 is directly connected, Vlan511

D       10.200.1.0/24 [90/3072] via 10.200.253.2, 3w0d, Port-channel1

D       10.205.1.0/24 [90/3072] via 10.200.253.2, 3w0d, Port-channel1

D       10.200.10.0/24 [90/3072] via 10.200.253.2, 3w0d, Port-channel1

D       10.200.1.9/32 [90/1536] via 10.200.253.2, 3w0d, Port-channel1

D       10.200.20.0/24 [90/3072] via 10.200.253.2, 3w0d, Port-channel1

     198.xx.xx.0/30 is subnetted, 2 subnets

D       198.xx.xx.x [90/429312] via 10.200.253.66, 3w0d, GigabitEthernet2/0/14

D EX    198.xx.xx.x

           [170/256256] via 10.200.253.66, 3w0d, GigabitEthernet2/0/14

D    192.168.100.0/24 [90/3072] via 10.200.253.2, 3w0d, Port-channel1

S*   0.0.0.0/0 [1/0] via 10.201.1.2

VCORE-6506#sh ip route eigrp

     10.0.0.0/8 is variably subnetted, 51 subnets, 6 masks

D EX    10.32.0.0/16 [170/256512] via 10.200.253.1, 03:43:06, Port-channel100

D EX    10.0.0.0/8 [170/145800192] via 10.200.199.3, 03:43:12, Vlan999

D       10.200.253.72/29 [90/28416] via 10.200.253.1, 3d20h, Port-channel100

     198.18.35.0/30 is subnetted, 2 subnets

D       198.18.35.4 [90/429568] via 10.200.253.1, 3w0d, Port-channel100

D EX    198.18.35.8 [170/256512] via 10.200.253.1, 3w0d, Port-channel100

D*EX 0.0.0.0/0 [170/256256] via 10.200.253.1, 7w0d, Port-channel100

So, the networks I'm looking for on the core switch are 10.75.0.0 and 10.74.193.0, of which are not being propagated from the edge switch to the core.  When I put those routes in as static on the core and point them to the edge switch as the next hop, the networks come back and everything works.  When I remove them, the stop working again.
When I do a traceroute from a machine to something on the network, it tries to go to the hsrp switch member with the core.  That's weird, since the gateway of last resort on the core should route those requests to the edge switch, I would think.
[root@rmf-fs01-lx ~]# traceroute 10.75.199.1
traceroute to 10.75.199.1 (10.75.199.1), 30 hops max, 40 byte packets
1  10.200.1.1 (10.200.1.1)  1.363 ms  1.345 ms  1.359 ms
2  10.200.199.3 (10.200.199.3)  0.676 ms  0.785 ms  0.996 ms
3  * * *
4  * * *
When this happened this morning, access to another one of my remote sites went down also (that's connected to that edge switch as well), but that one came back up again within a minute or so.  These other two networks, 10.75.0.0 and 10.74.193.0 didn't come back up and continue to be down. (unless I put those static routes in).  A sh log on both switches shows nothing.
Anyone have any ideas?  I tried to provide enough information upfront in hopes someone can help because I'm at a loss, and because I'm still trying to learn eigrp, my knowledge is limited.  My thought is that I could force an eigrp update between the two switches, but from what I've read it doesn't seem like a good idea to try to force anything.
Thanks!

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17 Replies 17

Ryan Fisher
Level 1
Level 1
In response to Richard Burts

‎01-09-2011 07:52 AM

ok, so I think that's correct with what happened, because when I sh ip route, all the networks are there, including the network to the remote site, 10.32.0.0.   So, then what I don't understand is, how is this 3650 switch picking up that external eigrp route (10.32.0.0) from the edge switch but it's not picking up the static routes for the 10.75.0.0 and 10.74.193.0 networks?  sh ip eigrp topology on the 3650 shows 10.32.0.0 coming from the core switch (10.200.199.2 -- 10.200.199.1 is the vip for hsrp)  And, since it's not getting it, how do I get the 3650 to pick those networks up with eigrp?

Also, is there a way to see HSRP events to see what happened, and what caused the failover to happen?   Thanks for the continued help!

DR13-3560#sh ip eigrp topology

EIGRP-IPv4 Topology Table for AS(100)/ID(10.200.199.3)

Codes: P - Passive, A - Active, U - Update, Q - Query, R - Reply,

       r - reply Status, s - sia Status

P 10.22.5.0/24, 0 successors, FD is Inaccessible

        via 10.200.199.2 (3072/2816), Vlan999

P 10.13.15.0/24, 0 successors, FD is Inaccessible

        via 10.200.199.2 (3072/2816), Vlan999

P 10.200.1.9/32, 1 successors, FD is 2816

        via 10.200.199.2 (2816/256), Vlan999

P 10.202.1.0/24, 1 successors, FD is 3072

        via 10.200.199.2 (3072/2816), Vlan999

P 10.19.1.0/24, 0 successors, FD is Inaccessible

        via 10.200.199.2 (3072/2816), Vlan999

P 10.3.10.0/24, 0 successors, FD is Inaccessible

        via 10.200.199.2 (3072/2816), Vlan999

P 10.32.0.0/16, 1 successors, FD is 256768, tag is 4323

        via 10.200.199.2 (256768/256512), Vlan999

P 10.20.5.0/24, 0 successors, FD is Inaccessible

        via 10.200.199.2 (3072/2816), Vlan999

P 10.13.10.0/24, 0 successors, FD is Inaccessible

        via 10.200.199.2 (3072/2816), Vlan999

P 10.5.2.0/24, 1 successors, FD is 3072

        via 10.200.199.2 (3072/2816), Vlan999

P 10.200.10.0/24, 1 successors, FD is 3072

        via 10.200.199.2 (3072/2816), Vlan999

P 10.1.0.0/16, 1 successors, FD is 3072

        via 10.200.199.2 (3072/2816), Vlan999

P 10.19.15.0/24, 0 successors, FD is Inaccessible

        via 10.200.199.2 (3072/2816), Vlan999

P 198.18.35.8/30, 1 successors, FD is 256768

        via 10.200.199.2 (256768/256512), Vlan999

P 192.168.100.0/24, 1 successors, FD is 3072

        via 10.200.199.2 (3072/2816), Vlan999

P 10.200.253.0/30, 1 successors, FD is 3072

        via 10.200.199.2 (3072/1536), Vlan999

P 10.0.0.0/8, 1 successors, FD is 256768

        via 10.200.199.2 (256768/256512), Vlan999

P 10.31.1.0/24, 0 successors, FD is Inaccessible

        via 10.200.199.2 (3072/2816), Vlan999

P 10.31.10.0/24, 0 successors, FD is Inaccessible

        via 10.200.199.2 (3072/2816), Vlan999

P 10.21.10.0/24, 0 successors, FD is Inaccessible

        via 10.200.199.2 (3072/2816), Vlan999

P 10.200.2.0/24, 1 successors, FD is 3072

        via 10.200.199.2 (3072/2816), Vlan999

P 10.205.1.0/24, 1 successors, FD is 3072

        via 10.200.199.2 (3072/2816), Vlan999

P 10.3.15.0/24, 0 successors, FD is Inaccessible

        via 10.200.199.2 (3072/2816), Vlan999

P 10.5.1.0/24, 0 successors, FD is Inaccessible

        via 10.200.199.2 (3072/2816), Vlan999

P 10.100.10.0/24, 1 successors, FD is 3072

        via 10.200.199.2 (3072/2816), Vlan999

P 10.200.1.0/24, 1 successors, FD is 3072

        via 10.200.199.2 (3072/2816), Vlan999

P 10.3.5.0/24, 0 successors, FD is Inaccessible

        via 10.200.199.2 (3072/2816), Vlan999

P 10.20.1.0/24, 0 successors, FD is Inaccessible

        via 10.200.199.2 (3072/2816), Vlan999

P 0.0.0.0/0, 0 successors, FD is Inaccessible

        via 10.200.199.2 (256512/256256), Vlan999

        via 10.13.253.4 (145799936/132999936), GigabitEthernet0/1

P 10.22.15.0/24, 0 successors, FD is Inaccessible

        via 10.200.199.2 (3072/2816), Vlan999

P 10.13.5.0/24, 0 successors, FD is Inaccessible

        via 10.200.199.2 (3072/2816), Vlan999

P 10.21.1.0/24, 0 successors, FD is Inaccessible

        via 10.200.199.2 (3072/2816), Vlan999

P 10.19.10.0/24, 0 successors, FD is Inaccessible

        via 10.200.199.2 (3072/2816), Vlan999

P 10.200.1.201/32, 1 successors, FD is 2816

        via 10.200.199.2 (2816/256), Vlan999

P 10.21.15.0/24, 0 successors, FD is Inaccessible

        via 10.200.199.2 (3072/2816), Vlan999

P 10.20.10.0/24, 0 successors, FD is Inaccessible

        via 10.200.199.2 (3072/2816), Vlan999

P 10.13.253.0/29, 1 successors, FD is 12825600

        via Connected, GigabitEthernet0/1

P 10.31.15.0/24, 0 successors, FD is Inaccessible

        via 10.200.199.2 (3072/2816), Vlan999

P 10.21.5.0/24, 0 successors, FD is Inaccessible

        via 10.200.199.2 (3072/2816), Vlan999

P 198.18.35.4/30, 1 successors, FD is 429824

        via 10.200.199.2 (429824/429568), Vlan999

P 10.100.1.0/24, 1 successors, FD is 3072

        via 10.200.199.2 (3072/2816), Vlan999

P 10.19.5.0/24, 0 successors, FD is Inaccessible

        via 10.200.199.2 (3072/2816), Vlan999

P 10.200.199.0/24, 1 successors, FD is 2816

        via Connected, Vlan999

P 10.200.3.0/24, 1 successors, FD is 3072

        via 10.200.199.2 (3072/2816), Vlan999

P 10.22.10.0/24, 0 successors, FD is Inaccessible

        via 10.200.199.2 (3072/2816), Vlan999

P 10.200.253.72/29, 1 successors, FD is 28672

        via 10.200.199.2 (28672/28416), Vlan999

P 10.13.1.0/24, 0 successors, FD is Inaccessible

        via 10.200.199.2 (3072/2816), Vlan999

P 10.200.20.0/24, 1 successors, FD is 3072

        via 10.200.199.2 (3072/2816), Vlan999

P 10.20.15.0/24, 0 successors, FD is Inaccessible

        via 10.200.199.2 (3072/2816), Vlan999

P 10.200.1.200/32, 1 successors, FD is 2816

        via 10.200.199.2 (2816/256), Vlan999

P 10.22.1.0/24, 0 successors, FD is Inaccessible

        via 10.200.199.2 (3072/2816), Vlan999

P 10.3.1.0/24, 0 successors, FD is Inaccessible

        via 10.200.199.2 (3072/2816), Vlan999

HSRP13-3560#sh ip eigrp neighbors
EIGRP-IPv4 Neighbors for AS(100)
H   Address                 Interface       Hold Uptime   SRTT   RTO  Q  Seq
                                            (sec)         (ms)       Cnt Num
1   10.200.199.2            Vl999             14 10:02:44   53   318  0  934
0   10.13.253.4             Gi0/1             12 10:02:51    2   200  0  350
(10.13.253.4 is the backup firewall for internet access...)

0 Helpful

Richard Burts
Hall of Fame
Hall of Fame
In response to Ryan Fisher

‎01-09-2011 02:27 PM

Ryan

There are still some things about your network topology and operating environment that are not clear to me. But the answer about 10.32 is clear and what to do about the missing networks is fairly clear (though there are several alternatives and you need to choose which is the best fit for your environment).

So first - about 10.32 - the edge switch has learned that route dynamically from another EIGRP neighbor (one of the ones that I do not know about) as shown in this from your original post:

D EX    10.32.0.0/16

           [170/256256] via 10.200.253.66, 03:45:24, GigabitEthernet2/0/14

As a dynamically learned route on the edge switch it is then advertised to the core switch via normal EIGRP processing. Since the core switch has learned this route dynamically then the core switch advertises it to the 3650. So now the 3650 knows 10.32 with the core as the next hop, and the core knows 10.32 with the edge as the next hop, and the edge knows 10.32 with 10.200.253.66 as the next hop.

So then - about the missing networks 10.75.0.0 and 10.74.193. This explanation is pretty simple. The edge switch knows these networks via static route. The edge switch redistributes static routes into EIGRP and the redistribution is controlled by the route map. The route map does permit redistribution of a default route and one other route. But it does not permit redistribution of 10.75.0.0 and 10.74.193. Since these routes are not redistributed they are not advertised to the core. And the core can not advertise them to the 3650.

So now that we understand (I think) the problem, then what are the possible solutions. There are multiple ways that you can solve this problem. I will list several of the alternatives, with my preferred alternative at the top of the list:

- you can add commands in the prefix list on the edge switch to permit 10.75.0.0 and 10.74.193.0. If they are permitted in the prefix list then they will be advertised to the core, and from the core advertised to the 3650. This is a very simple and effective solution and allows the network to dynamically react to changes in the network, which is one of the main reasons that we run dynamic routing protocols.

- you could configure a static route on the core for 10.75.0.0 and 10.74.193.0.

- if you use the static route alternative on the core then you might want to consider doing redistribution of static routes into EIGRP so that the core can advertise the networks to the 3650.

- you could configure a static rotue on the 3650 for 10.75.0.0 and 10.74.193..

HTH

Rick

HTH

Rick
0 Helpful

Ryan Fisher
Level 1
Level 1
In response to Richard Burts

‎01-09-2011 03:04 PM

Yes, very true.  I bet the 10.32 network is getting learned from the router to the remote site, 10.200.253.66, which is probably where that static route is.  So, what my topology is basically right now, is:

6500 core  -->  3705 edge  -->  2901 router (10.200.253.66/29)  --> MPLS -->  remote site (10.32.0.0)

                                        -->  2811 router (10.200.253.74/29)  -->  DR site (10.75.0.0, 10.74.193.0)

Right now I still have the DR network onsite as I am still building it out before I ship.  So basically I have a routed interface on the edge switch (10.200.253.73) to my DR router (fa0/0 10.200.253.74 fa0/1 10.74.193.2) to my dr network switch (10.74.193.1).

So, I think what I can do for now until I move it is put the commands prefix list on the edge switch to permit those routes to be advertised.  Then, once I move the DR network out to its coLo, I'll add those static routes to the 2901 router (because we have an MPLS network) and those routes will then be advertised the same way as the 10.32 routes.  I think that sounds like a good plan.

Thanks a lot for sticking this out with me and helping me out.  I feel I've really learned a lot from dealing with this issue this weekend, and your (and everyone else that provided input) helped me out a lot, so thanks!

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