Solved: Flapping VLAN in c 2960X switch - Page 3

rsthakur · ‎02-08-2021

We receive such log in 2960 X switch. Find attach switch configuration and image version.

.Feb 8 15:35:10: %LINEPROTO-5-UPDOWN: Line protocol on Interface Vlan5, changed state to down
.Feb 8 15:35:10: %LINEPROTO-5-UPDOWN: Line protocol on Interface Vlan19, changed state to up
.Feb 8 15:35:11: %LINEPROTO-5-UPDOWN: Line protocol on Interface Vlan5, changed state to up
.Feb 8 15:35:11: %LINEPROTO-5-UPDOWN: Line protocol on Interface Vlan19, changed state to down
.Feb 8 15:35:12: %LINEPROTO-5-UPDOWN: Line protocol on Interface Vlan5, changed state to down
.Feb 8 15:35:12: %LINEPROTO-5-UPDOWN: Line protocol on Interface Vlan19, changed state to up
.Feb 8 15:35:13: %LINEPROTO-5-UPDOWN: Line protocol on Interface Vlan19, changed state to down
.Feb 8 15:35:14: %LINEPROTO-5-UPDOWN: Line protocol on Interface Vlan5, changed state to up
.Feb 8 15:35:14: %LINEPROTO-5-UPDOWN: Line protocol on Interface Vlan5, changed state to down
.Feb 8 15:35:14: %LINEPROTO-5-UPDOWN: Line protocol on Interface Vlan19, changed state to up
.Feb 8 15:35:16: %LINEPROTO-5-UPDOWN: Line protocol on Interface Vlan5, changed state to up
.Feb 8 15:35:19: %LINEPROTO-5-UPDOWN: Line protocol on Interface Vlan5, changed state to down
.Feb 8 15:35:20: %LINEPROTO-5-UPDOWN: Line protocol on Interface Vlan5, changed state to up
.Feb 8 15:35:21: %LINEPROTO-5-UPDOWN: Line protocol on Interface Vlan5, changed state to down
.Feb 8 15:35:22: %LINEPROTO-5-UPDOWN: Line protocol on Interface Vlan5, changed state to up
.Feb 8 15:35:30: %LINEPROTO-5-UPDOWN: Line protocol on Interface Vlan19, changed state to down
.Feb 8 15:35:30: %LINEPROTO-5-UPDOWN: Line protocol on Interface Vlan19, changed state to up
.Feb 8 15:35:32: %LINEPROTO-5-UPDOWN: Line protocol on Interface Vlan19, changed state to down
.Feb 8 15:35:32: %LINEPROTO-5-UPDOWN: Line protocol on Interface Vlan5, changed state to down
.Feb 8 15:35:32: %LINEPROTO-5-UPDOWN: Line protocol on Interface Vlan5, changed state to up
.Feb 8 15:35:32: %LINEPROTO-5-UPDOWN: Line protocol on Interface Vlan19, changed state to up
.Feb 8 15:35:37: %LINEPROTO-5-UPDOWN: Line protocol on Interface Vlan5, changed state to down
.Feb 8 15:35:38: %LINEPROTO-5-UPDOWN: Line protocol on Interface Vlan5, changed state to up
.Feb 8 15:35:39: %LINEPROTO-5-UPDOWN: Line protocol on Interface Vlan5, changed state to down
.Feb 8 15:35:41: %LINEPROTO-5-UPDOWN: Line protocol on Interface Vlan5, changed state to up
.Feb 8 15:35:42: %LINEPROTO-5-UPDOWN: Line protocol on Interface Vlan5, changed state to down
.Feb 8 15:35:43: %LINEPROTO-5-UPDOWN: Line protocol on Interface Vlan5, changed state to up
.Feb 8 15:35:44: %LINEPROTO-5-UPDOWN: Line protocol on Interface Vlan5, changed state to down
.Feb 8 15:35:45: %LINEPROTO-5-UPDOWN: Line protocol on Interface Vlan5, changed state to up
.Feb 8 15:35:59: %LINEPROTO-5-UPDOWN: Line protocol on Interface Vlan5, changed state to down
.Feb 8 15:36:00: %LINEPROTO-5-UPDOWN: Line protocol on Interface Vlan5, changed state to up
.Feb 8 15:36:09: %LINEPROTO-5-UPDOWN: Line protocol on Interface Vlan19, changed state to down
.Feb 8 15:36:09: %LINEPROTO-5-UPDOWN: Line protocol on Interface Vlan5, changed state to down
.Feb 8 15:36:09: %LINEPROTO-5-UPDOWN: Line protocol on Interface Vlan5, changed state to up
.Feb 8 15:36:09: %LINEPROTO-5-UPDOWN: Line protocol on Interface Vlan19, changed state to up
.Feb 8 15:36:13: %LINEPROTO-5-UPDOWN: Line protocol on Interface Vlan19, changed state to down
.Feb 8 15:36:13: %LINEPROTO-5-UPDOWN: Line protocol on Interface Vlan5, changed state to down
.Feb 8 15:36:13: %LINEPROTO-5-UPDOWN: Line protocol on Interface Vlan19, changed state to up
.Feb 8 15:36:14: %LINEPROTO-5-UPDOWN: Line protocol on Interface Vlan5, changed state to up
.Feb 8 15:36:16: %LINEPROTO-5-UPDOWN: Line protocol on Interface Vlan5, changed state to down
.Feb 8 15:36:17: %LINEPROTO-5-UPDOWN: Line protocol on Interface Vlan5, changed state to up

rsthakur · ‎02-11-2021

@Leo Laohoo . @balaji.bandi . @Scott Leport . @pieterh

After a long discussion finally, I got the solution. It is a spanning tree related problem.

Thanks to everyone to provide valuable knowledge and support.

Scott Leport · ‎02-12-2021

Hi @rsthakur

Glad to hear you have a solution....and on a Friday too! Nice way to end the week.

For my own curiosity, what was the issue? Rapid-PVST? Wrong root bridge? Or something else entirely?

rsthakur · ‎02-12-2021

The issue is related to Spanning tree enabled protocol IEEE

here is a Cisco reference for this
search for diameter

pieterh · ‎02-09-2021

I do not agree!
I checked on our switches, only where an IP-phone is connected, both vlans will show

Scott Leport · ‎02-10-2021

Lets agree to disagree then!

I checked a switch where I know an IP phone isn't connected which is configured for both the access and voice VLAN and both VLANs show.

In any case, sounds like the OP has a different issue.

pieterh · ‎02-10-2021

You are right let's concentrate on the question
rsthakur tested the additional command , no change in behavior (post 09-02-2021 12:50 PM)

rsthakur · ‎02-09-2021

We add "switchport mode access" but no change(same log vlan 19 UP/DOWN)

If we remove 2960 S series switch from subnet then everythink work fine.

#sh vla brief

VLAN Name Status Ports
---- -------------------------------- --------- -------------------------------
1 default active Te1/0/1, Te1/0/2
5 VLAN0005 active Gi1/0/1, Gi1/0/2, Gi1/0/3
Gi1/0/4, Gi1/0/5, Gi1/0/6
Gi1/0/7, Gi1/0/8, Gi1/0/9
Gi1/0/10, Gi1/0/11, Gi1/0/12

.Feb 9 17:16:09: %LINEPROTO-5-UPDOWN: Line protocol on Interface Vlan19, changed state to down
.Feb 9 17:16:09: %LINEPR Gi1/0/13, Gi1/0/14, Gi1/0/15
Gi1/0/16, Gi1/0/17, Gi1/0/18
Gi1/0/19, Gi1/0/20, Gi1/0/21
Gi1/0/22, Gi1/0/23, Gi1/0/24
11 VLAN0011 active
12 VLAN0012 active
13 VLAN0013 active
14 VLAN0014 active
15 OTO-5-UPDOWN: Line protocol on Interface Vlan19, changed state to up VLAN0015 active
16 VLAN0016 active
17 VLAN0017 active
18 VLAN0018 active
19 VLAN0019 active Gi1/0/1, Gi1/0/2, Gi1/0/3
Gi1/0/4, Gi1/0/5, Gi1/0/6
Gi1/0/7, Gi1/0/8, Gi1/0/9

VLAN Name Status Ports
---- -------------------------------- --------- -------------------------------
Gi1/0/10, Gi1/0/11, Gi1/0/12
Gi1/0/13, Gi1/0/14, Gi1/0/15
Gi1/0/16, Gi1/0/17, Gi1/0/18
Gi1/0/19, Gi1/0/20, Gi1/0/21
Gi1/0/22, Gi1/0/23, Gi1/0/24
20 VLAN0020 active
21 VLAN0021 active
22 VLAN0022 active
23 VLAN0023 active
24 VLAN0024 active
26 VLAN0026 active
27 VLAN0027 active
28 VLAN0028 active
30 VLAN0030 active
41 VLAN0041 active
42 VLAN0042 active
51 VLAN0051 active
52 VLAN0052 active
53 VLAN0053 active
54 VLAN0054 active
55 VLAN0055 active
56 VLAN0056 active
57 VLAN0057 active

VLAN Name Status Ports
---- -------------------------------- --------- -------------------------------
99 VLAN0099 active
100 VLAN0100 active
101 VLAN0101 active
102 VLAN0102 active
111 VLAN0111 active
112 VLAN0112 active
113 VLAN0113 active
114 VLAN0114 active
115 VLAN0115 active
116 VLAN0116 active
120 VLAN0120 active
121 VLAN0121 active
122 VLAN0122 active
123 VLAN0123 active
124 VLAN0124 active
125 VLAN0125 active
126 VLAN0126 active
127 VLAN0127 active
128 VLAN0128 active
129 VLAN0129 active
130 VLAN0130 active
131 VLAN0131 active
132 VLAN0132 active

VLAN Name Status Ports
---- -------------------------------- --------- -------------------------------
133 VLAN0133 active
134 VLAN0134 active
135 VLAN0135 active
136 VLAN0136 active
137 VLAN0137 active
138 VLAN0138 active
139 VLAN0139 active
140 VLAN0140 active
142 VLAN0142 active
143 VLAN0143 active
500 VLAN0500 active
1002 fddi-default act/unsup
1003 token-ring-default act/unsup
1004 fddinet-default act/unsup
1005 trnet-default act/unsup

pieterh · ‎02-10-2021

>>> If we connected any device on that switch then we did not recieve any flapping, but we getting drop in data and voice and ping also.<<<

sounds like a spanning-tree issue, but you do not mention any logs entries about spanning-tree
when a topology change occurs spanning-tree changes into learning-state before going into forwarding state again

2960X interface G1/0/23 (mode trunk) is connected upstream to an 6809 ?
which switch is the spanning-tree root?
how is rest of spanning-tree topology?

and how is the port(s) on the uplink switch configured?

rsthakur · ‎02-10-2021

2960X interface G1/0/23 (mode trunk) is connected upstream to a 6809?

No, 64.60(x series) is connected to 64.61 and 64.61(x series) is connected to 64.62(S series) and so on till 64.66.

attach uplink map notepad for better help.

which switch is the spanning-tree root?
how is rest of spanning-tree topology?

Sorry not getting it.

and how is the port(s) on the uplink switch configured?

In all switch uplink port (gi1/0/23-24) is the trunk.

pieterh · ‎02-10-2021

switches use a technique called spanning-tree to prevent loops in the network
also one switch acts as a master (the spanning-tree root)

when you add/remove a switch the topology changes,
as a result of this change the topology wil be analyzed to check there are still no loops
and another switch may be selected to take the root-role
during this analysis no data will be sent over the network, hence data/voice/ping drops

how many switches in total are involved? (there is a maximum number of switches to put in a row)

rsthakur · ‎02-10-2021

Total 6 Number of the switch is involved(60 to 66) and how to find which switch act as a master.

pieterh · ‎02-10-2021

60 - 66 = 7 switches not 6
and there is two more switches

BackBone         Gig 1/0/25        154             R S I  C6807-XL  Gig 1/5
Acad3_Test_28.64.65
                 Gig 1/0/23        170              S I   WS-C2960X Gig 1/0/2

and maybe more switches connected to the backbone ????

try reconfiguring your connections more like a tree than a chain
you are allready touching the max that i referred to (max 7 hops between ANY two switches on your network
if you've got another similar string connected to the backbone you are over the 7 hops limit

backbone
|---64.66--64.65--64.64--64.63--64.62--64.61--64.60
|
|----acad3

change it to something like

backbone
| | |--64.66--64.65--64.64
| |---64.63--64.62--64.61--64.60
|----acad3

rsthakur · ‎02-10-2021

I got it, But I running STAR Topology in our campus and recently more than 27 subnets is running and in signal subnet mote than 50 switches is connected in a series.

Can I get any document where is max hop limit is defined?

pieterh · ‎02-11-2021

it should be in the IEEE 802.1d spanning tree standard.

here is a Cisco reference for this
search for diameter

(Optional) For diameter net-diameter , specify the maximum number of switches between any two end stations. The range is 2 to 7.

NB! Cisco mentions "between endpoints" so even stricter than between switches !!!
There is an option to migrate from PVST+ (Cisco's default) to MST, MST spanning-trees can "reach" further away.(max 255)
but of course this needs planning

balaji.bandi · ‎02-09-2021

is this switch acting as Layer 2 or Layer3 ? i only see 1 VLAn Interface for VLAN 19, i do not see any Interface vlan 5 (or i am missing something here ?) - please confirm the ports in access mode ?

is this correct. - where is VLAN 5 interface ?

interface Vlan19
 ip address 172.28.64.60 255.255.248.0
 no ip route-cache
!
ip default-gateway 172.28.71.254

BB

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