2

I believe I am missing something obvious. I am using GNS3 to lab out having two paths to a CORE network. See picture. The configuration works as I imagined, I can ping from each Switch every other Switch within VLAN212. I can also ping the loopbacks of the CORE switch from the other switches in the VLAN212 domain. Spanning tree has put SW-C f/15 in block mode which is good since this group of switches is a Layer 2 loop. The issue is, if I remove any of the links in the loop, the topology cannot recover. I thought Spanning Tree would only take 30 seconds to recalculate, but something else is preventing each switch to ping each other...Even in the localized VLAN 212. What I mean is if I remove the link from SW-A --> SW-C. I can no longer ping from SW-C any of the switches or even the CORE switch.

Perhaps I am going about this the wrong way. If there is a better way to get a secondary path to a group of non-stackable switches let me know. I am trying to get away from the fact that these non-stackable switches are daisy chained, with only 1 switch having a path to the core.

Any, I appreciate your help. Thank you!

Picture.enter image description here

Spanning Tree output SW-C with link intact:

SW-C#show spanning-tree brief

VLAN212
  Spanning tree enabled protocol ieee
  Root ID    Priority    32768
             Address     c801.2308.0001
             Cost        19
             Port        55 (FastEthernet1/14)
             Hello Time   2 sec  Max Age 20 sec  Forward Delay 15 sec

  Bridge ID  Priority    32768
             Address     c802.2308.0000
             Hello Time   2 sec  Max Age 20 sec  Forward Delay 15 sec
             Aging Time 300

Interface                                   Designated
Name                 Port ID Prio Cost  Sts Cost  Bridge ID            Port ID
-------------------- ------- ---- ----- --- ----- -------------------- -------
FastEthernet1/14     128.55   128    19 FWD     0 32768 c801.2308.0001 128.56
FastEthernet1/15     128.56   128    19 FWD    19 32768 c802.2308.0000 128.56

SW-C#ping 1.1.1.1

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 1.1.1.1, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 20/45/84 ms

REmove link from SW-A to SW-C

SW-C#show spanning-tree bri

VLAN212
  Spanning tree enabled protocol ieee
  Root ID    Priority    32768
             Address     c801.2308.0001
             Cost        19
             Port        55 (FastEthernet1/14)
             Hello Time   2 sec  Max Age 20 sec  Forward Delay 15 sec

  Bridge ID  Priority    32768
             Address     c802.2308.0000
             Hello Time   2 sec  Max Age 20 sec  Forward Delay 15 sec
             Aging Time 300

Interface                                   Designated
Name                 Port ID Prio Cost  Sts Cost  Bridge ID            Port ID
-------------------- ------- ---- ----- --- ----- -------------------- -------
FastEthernet1/14     128.55   128    19 FWD     0 32768 c801.2308.0001 128.56
FastEthernet1/15     128.56   128    19 FWD    19 32768 c802.2308.0000 128.56

SW-C#
*Mar  1 00:09:52.311: %DUAL-5-NBRCHANGE: IP-EIGRP(0) 1: Neighbor 10.0.0.11 (Vla                                                                             n212) is down: holding time expired
SW-C#
*Mar  1 00:09:55.903: %DUAL-5-NBRCHANGE: IP-EIGRP(0) 1: Neighbor 10.0.0.2 (Vlan                                                                             212) is down: holding time expired
SW-C#ping 1.1.1.1

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 1.1.1.1, timeout is 2 seconds:
.....
Success rate is 0 percent (0/5)

ADDING SW RUNNING_CONFIGS

CORE

version 12.4
service timestamps debug datetime msec
service timestamps log datetime msec
no service password-encryption
!
hostname CORE
!
boot-start-marker
boot-end-marker
!
!
no aaa new-model
memory-size iomem 15
no ip icmp rate-limit unreachable
ip cef
!
!
!
!
no ip domain lookup
!
!
!
!
!
ip tcp synwait-time 5
!
!
interface Loopback0
 ip address 1.1.1.1 255.255.255.0
!
interface Loopback1
 ip address 2.2.2.2 255.255.255.0
!
interface Loopback2
 ip address 3.3.3.3 255.255.255.0
!
interface FastEthernet0/0
 no ip address
 shutdown
 duplex auto
 speed auto
!
interface FastEthernet0/1
 no ip address
 shutdown
 duplex auto
 speed auto
!
interface FastEthernet1/0
!
interface FastEthernet1/1
 switchport access vlan 295
!
interface FastEthernet1/2
 switchport access vlan 296
!
interface FastEthernet1/3
!
interface FastEthernet1/4
!
interface FastEthernet1/5
!
interface FastEthernet1/6
!
interface FastEthernet1/7
!
interface FastEthernet1/8
!
interface FastEthernet1/9
!
interface FastEthernet1/10
!
interface FastEthernet1/11
!
interface FastEthernet1/12
!
interface FastEthernet1/13
!
interface FastEthernet1/14
!
interface FastEthernet1/15
!
interface Vlan1
 no ip address
!
interface Vlan295
 ip address 172.16.0.1 255.255.255.0
 ip summary-address eigrp 1 0.0.0.0 0.0.0.0
!
interface Vlan296
 ip address 172.16.1.1 255.255.255.0
 ip summary-address eigrp 1 0.0.0.0 0.0.0.0
!
router eigrp 1
 network 172.16.0.0 0.0.0.255
 network 172.16.1.0 0.0.0.255
 no auto-summary
!
ip forward-protocol nd
!
no ip http server
no ip http secure-server
!
!
control-plane
!
!
line con 0
 exec-timeout 0 0
 privilege level 15
 logging synchronous
line aux 0
 exec-timeout 0 0
 privilege level 15
 logging synchronous
line vty 0 4
 login
!
!
end

SW-A

version 12.4
service timestamps debug datetime msec
service timestamps log datetime msec
no service password-encryption
!
hostname SW-A
!
boot-start-marker
boot-end-marker
!
!
no aaa new-model
memory-size iomem 15
no ip icmp rate-limit unreachable
ip cef
!
!
!
!
no ip domain lookup
!
!
!
!
!
ip tcp synwait-time 5
!
!
interface FastEthernet0/0
 no ip address
 shutdown
 duplex auto
 speed auto
!
interface FastEthernet0/1
 no ip address
 shutdown
 duplex auto
 speed auto
!
interface FastEthernet1/0
!
interface FastEthernet1/1
 switchport access vlan 295
!
interface FastEthernet1/2
!
interface FastEthernet1/3
!
interface FastEthernet1/4
!
interface FastEthernet1/5
!
interface FastEthernet1/6
!
interface FastEthernet1/7
!
interface FastEthernet1/8
!
interface FastEthernet1/9
!
interface FastEthernet1/10
!
interface FastEthernet1/11
!
interface FastEthernet1/12
!
interface FastEthernet1/13
!
interface FastEthernet1/14
 switchport access vlan 212
!
interface FastEthernet1/15
 switchport access vlan 212
!
interface Vlan1
 no ip address
!
interface Vlan212
 ip address 10.0.0.1 255.255.255.0
!
interface Vlan295
 ip address 172.16.0.2 255.255.255.0
!
router eigrp 1
 network 0.0.0.0
 no auto-summary
!
ip forward-protocol nd
!
no ip http server
no ip http secure-server
!
!
control-plane
!
!
line con 0
 exec-timeout 0 0
 privilege level 15
 logging synchronous
line aux 0
 exec-timeout 0 0
 privilege level 15
 logging synchronous
line vty 0 4
 login
!
!
end

SW-B

version 12.4
service timestamps debug datetime msec
service timestamps log datetime msec
no service password-encryption
!
hostname SW-B
!
boot-start-marker
boot-end-marker
!
!
no aaa new-model
memory-size iomem 15
no ip icmp rate-limit unreachable
ip cef
!
!
!
!
no ip domain lookup
!
!
!
!
!
ip tcp synwait-time 5
!
!
interface FastEthernet0/0
 no ip address
 shutdown
 duplex auto
 speed auto
!
interface FastEthernet0/1
 no ip address
 shutdown
 duplex auto
 speed auto
!
interface FastEthernet1/0
!
interface FastEthernet1/1
 switchport access vlan 296
!
interface FastEthernet1/2
!
interface FastEthernet1/3
!
interface FastEthernet1/4
!
interface FastEthernet1/5
!
interface FastEthernet1/6
!
interface FastEthernet1/7
!
interface FastEthernet1/8
!
interface FastEthernet1/9
!
interface FastEthernet1/10
!
interface FastEthernet1/11
!
interface FastEthernet1/12
!
interface FastEthernet1/13
!
interface FastEthernet1/14
 switchport access vlan 212
!
interface FastEthernet1/15
 switchport access vlan 212
!
interface Vlan1
 no ip address
!
interface Vlan212
 ip address 10.0.0.2 255.255.255.0
!
interface Vlan296
 ip address 172.16.1.2 255.255.255.0
!
router eigrp 1
 network 0.0.0.0
 no auto-summary
!
ip forward-protocol nd
!
no ip http server
no ip http secure-server
!
mac-address-table static c809.094c.0000 interface FastEthernet1/14 vlan 1
!
control-plane
!
!
line con 0
 exec-timeout 0 0
 privilege level 15
 logging synchronous
line aux 0
 exec-timeout 0 0
 privilege level 15
 logging synchronous
line vty 0 4
 login
!
!
end

SW-C

version 12.4
service timestamps debug datetime msec
service timestamps log datetime msec
no service password-encryption
!
hostname SW-C
!
boot-start-marker
boot-end-marker
!
!
no aaa new-model
memory-size iomem 15
no ip icmp rate-limit unreachable
ip cef
!
!
!
!
no ip domain lookup
!
!
!
!
!
ip tcp synwait-time 5
!
!
interface FastEthernet0/0
 no ip address
 shutdown
 duplex auto
 speed auto
!
interface FastEthernet0/1
 no ip address
 shutdown
 duplex auto
 speed auto
!
interface FastEthernet1/0
!
interface FastEthernet1/1
!
interface FastEthernet1/2
!
interface FastEthernet1/3
!
interface FastEthernet1/4
!
interface FastEthernet1/5
!
interface FastEthernet1/6
!
interface FastEthernet1/7
!
interface FastEthernet1/8
!
interface FastEthernet1/9
!
interface FastEthernet1/10
!
interface FastEthernet1/11
!
interface FastEthernet1/12
!
interface FastEthernet1/13
!
interface FastEthernet1/14
 switchport access vlan 212
!
interface FastEthernet1/15
 switchport access vlan 212
!
interface Vlan1
 no ip address
!
interface Vlan212
 ip address 10.0.0.10 255.255.255.0
!
router eigrp 1
 network 0.0.0.0
 no auto-summary
!
ip forward-protocol nd
!
no ip http server
no ip http secure-server
!
mac-address-table static c80a.094c.0000 interface FastEthernet1/15 vlan 212
!
control-plane
!
!
line con 0
 exec-timeout 0 0
 privilege level 15
 logging synchronous
line aux 0
 exec-timeout 0 0
 privilege level 15
 logging synchronous
line vty 0 4
 login
!
!
end

SW-D

version 12.4
service timestamps debug datetime msec
service timestamps log datetime msec
no service password-encryption
!
hostname SW-D
!
boot-start-marker
boot-end-marker
!
!
no aaa new-model
memory-size iomem 15
no ip icmp rate-limit unreachable
ip cef
!
!
!
!
no ip domain lookup
!
!
!
!
!
ip tcp synwait-time 5
!
!
interface FastEthernet0/0
 no ip address
 shutdown
 duplex auto
 speed auto
!
interface FastEthernet0/1
 no ip address
 shutdown
 duplex auto
 speed auto
!
interface FastEthernet1/0
!
interface FastEthernet1/1
!
interface FastEthernet1/2
!
interface FastEthernet1/3
!
interface FastEthernet1/4
!
interface FastEthernet1/5
!
interface FastEthernet1/6
!
interface FastEthernet1/7
!
interface FastEthernet1/8
!
interface FastEthernet1/9
!
interface FastEthernet1/10
!
interface FastEthernet1/11
!
interface FastEthernet1/12
!
interface FastEthernet1/13
!
interface FastEthernet1/14
 switchport access vlan 212
!
interface FastEthernet1/15
 switchport access vlan 212
!
interface Vlan1
 no ip address
!
interface Vlan212
 ip address 10.0.0.11 255.255.255.0
!
router eigrp 1
 network 0.0.0.0
 no auto-summary
!
ip forward-protocol nd
!
no ip http server
no ip http secure-server
!
!
control-plane
!
!
line con 0
 exec-timeout 0 0
 privilege level 15
 logging synchronous
line aux 0
 exec-timeout 0 0
 privilege level 15
 logging synchronous
line vty 0 4
 login
!
!
end

HERE IS AN EXAMPLE OF REMOVE THE LINK BETWEEN SW C and B, and then readding the link.

SW-C#ping 1.1.1.1 repeat 100000

Type escape sequence to abort.
Sending 100000, 100-byte ICMP Echos to 1.1.1.1, timeout is 2 seconds:
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!.!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
!........
*Mar  1 00:32:23.183: %DUAL-5-NBRCHANGE: IP-EIGRP(0) 1: Neighbor 10.0.0.2 (Vlan212) is down: holding time expired................!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
*Mar  1 00:32:55.739: %DUAL-5-NBRCHANGE: IP-EIGRP(0) 1: Neighbor 10.0.0.2 (Vlan212) is up: new adjacency!!!!!!!
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
!!!!!!!!!!!!!!!!!!!!!!!!!!!!..........................................
.........................................................

For some reason it never recovers....

Improve this question
8
  • What is the output on Sw C of show spanning-tree vlan 212?
    – Ron Trunk
    Jan 30, 2014 at 20:23
  • What does that output look like with the link disabled?
    – Dave in Ohio
    Jan 30, 2014 at 21:17
  • @Jim the new show command is different than before. fa 1/15 is no longer blocking. So what did you do differently this time?
    – Ron Trunk
    Jan 30, 2014 at 21:29
  • @Jim Notice that in the second listing (with link removed) you still hear BPDUs from port 1/14. So that means the link isn't actually removed. How, exactly, are you removing the link?
    – Ron Trunk
    Jan 30, 2014 at 21:36
  • How is your EIGRP configured on these switches? Notice that in your second output you appear to lose EIGRP neighbors.
    – Dave in Ohio
    Jan 30, 2014 at 22:13

2 Answers 2

Reset to default
3

The first thing that jumps out at me is you say you removed the link from A to C, but fa 1/14 is still in the forwarding state. That means the port is still up.

The second thing I notice is that the root port is also 1/14, which means it's up and hearing BPDUs from sw A. So I would guess you didn't really remove the link from A to C, but blocked traffic in some other way.

Improve this answer
5
  • You want me to remove the link and give you the spanning tree summary?
    – Jim
    Jan 30, 2014 at 21:19
  • @jim Your new edits are different that earlier show command. What is different?
    – Ron Trunk
    Jan 30, 2014 at 21:30
  • I re added the link in order to take the two screenshots of before and after.
    – Jim
    Jan 31, 2014 at 14:31
  • It seems like only if I reboot all the routers in the layer 2 domain, it will start pinging again...
    – Jim
    Jan 31, 2014 at 15:54
  • @jim, can you join me in the general network engineering chat room?
    – Ron Trunk
    Jan 31, 2014 at 16:05
2

This is an issue with GNS3. If you try to right-click and remove the link, GNS3 still reports to each switch that the link is still there. Use "shutdown" command to turn off the interfaces involved in the link.

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