01-22-2013 07:09 AM - edited 03-07-2019 11:14 AM
Good morning,
A couple of weeks ago we upgraded about 50 access layer switches at a branch office. All of them are WS-3560-24PS. The switches were upgraded to IOS 12.2(55)SE6. Once the update was completed, all of the switches were reloaded to complete the upgrade. One of the 50 switches showed up in our monitoring application as being down after the reload. We had someone at the office plug in a laptop so we could console into it and the switch configuration looked correct. The switch is working normally (PC's and phones working normally), but we cannot ping or telnet into this one switch. Below is a breakdown of this site in terms of topology:
Core - 2 6509
Distribution - 2 3750g
Access - 3560 switches
Layer two looks to be running normally in that vtp is being updated and cdp is working as well. The trunk interfaces from this switch to the distribution layer switch are up (each gig interface on this 3560 goes to one of the 3705g switches).
On this switch, I have erased the config and deleted the vlan.dat. I reapplied the config and re-enabled VTP and this switch is still not accessible. Any suggestions?
I should mention that the management interface is vlan 1. I have tried giving this management interface a different IP address in case there was a duplicate IP and that does not work. Other switches that were upgraded and connect up into this 3750g stack work fine.
Solved! Go to Solution.
02-11-2013 02:10 PM
Charlie
thats great news, but unfortunate in a way that it was not found eariler
Not my text but the; “vlan dot1q tag native” which will prevent the double-encapsulation attacks. This command globally works on all switchport trunks on that entire Ethernet switch. This command will make sure that the native VLAN is always tagged on every trunk on the switch. This is a great best practice and takes care of the issue with a single command. This command should be entered in every switch in the campus." (my bold)
This caused every untagged ingress frame is dropped, so the traffic replies were not reaching the control plane of the switch.
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01-22-2013 07:37 AM
Hi
Can the switch ping out to the network? is the ip default-gateway set?
Regards
Stephen
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01-22-2013 07:59 AM
HI,
The switch cannot ping out. The default gateway is set as well.
01-22-2013 08:04 AM
can you provide partial relevant configuration? Also, try a debug ip icmp when pinging it to see if the icmp packets are reaching the switch
Regards
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01-22-2013 08:14 AM
I enabled ICMP debugging. I pinged the switch from another switch in this IDF and nothing shows in the log of the failed switch.
Interface Vlan1
ip address 10.19.0.112 255.255.255.0
ip default-gateway 10.19.0.1
ip classless
01-22-2013 08:04 AM
Make sure ip routing is not turned on the 3560, otherwise the default gateway statement is no good. If routing is turned on then you would need a default static route pointing to the 3750 gateway address for that vlan and get rid of the default gateway statement. Is this switch trunked or just an access port ? Check trunk setup , native vlan for trunk etc... You should be able to get to the switch from 3750 even if the gateway is no good because it is directly attached to the 3750 which is where i assume the vlan 1 subnet originates. Source ping the switch from the vlan 1 SVI .
01-22-2013 09:00 AM
Perhaps the output of show ip interface brief or of show interface status might shed some light on the issue?
I also wonder what would be in the output of show arp from the problem switch.
HTH
Rick
01-22-2013 09:04 AM
Here is the information you requested.
Interface IP-Address OK? Method Status Protocol
Vlan1 10.19.0.112 YES manual up up
FastEthernet0/1 unassigned YES unset down down
FastEthernet0/2 unassigned YES unset up up
FastEthernet0/3 unassigned YES unset up up
FastEthernet0/4 unassigned YES unset down down
FastEthernet0/5 unassigned YES unset down down
FastEthernet0/6 unassigned YES unset up up
FastEthernet0/7 unassigned YES unset up up
FastEthernet0/8 unassigned YES unset up up
FastEthernet0/9 unassigned YES unset up up
FastEthernet0/10 unassigned YES unset up up
FastEthernet0/11 unassigned YES unset up up
FastEthernet0/12 unassigned YES unset up up
FastEthernet0/13 unassigned YES unset up up
FastEthernet0/14 unassigned YES unset down down
FastEthernet0/15 unassigned YES unset up up
FastEthernet0/16 unassigned YES unset down down
FastEthernet0/17 unassigned YES unset up up
FastEthernet0/18 unassigned YES unset up up
FastEthernet0/19 unassigned YES unset down down
FastEthernet0/20 unassigned YES unset up up
FastEthernet0/21 unassigned YES unset up up
FastEthernet0/22 unassigned YES unset up up
FastEthernet0/23 unassigned YES unset down down
FastEthernet0/24 unassigned YES unset up up
GigabitEthernet0/1 unassigned YES unset up up
GigabitEthernet0/2 unassigned YES unset up up
sh arp
Protocol Address Age (min) Hardware Addr Type Interface
Internet 10.19.0.1 0 Incomplete ARPA
Internet 10.19.0.112 - 001b.0c7c.1340 ARPA Vlan1
01-22-2013 09:10 AM
Thanks for the information. It is somewhat helpful, but not enough to diagnose the full problem. It does confirm the IP address of the VLAN interface seems to be correct.
The fact that the arp table shows incomplete for the mac address of the gateway 10.19.0.1 indicates that arp is failing to resolve the IP address to a mac address. This typically indicates some layer 2 problem. Can you post the output of show interface status, and indentify for us the ports on the switch that connect to the upstream switch?
HTH
Rick
01-22-2013 09:27 AM
You may also want to check what vlans are allowed an the upstream trunk links with a show int trunk. Do this on both sides of the trunks from the affected switch and ensure vlan1 is allowed
Regards
Sent from Cisco Technical Support iPhone App
01-22-2013 09:34 AM
I think this will hit the last two questions. I compared this output to another switch that we upgraded, and the information matches the functional switch.
Trunks on problematic switch
Gi0/1 connected trunk full 1000 10/100/1000BaseTX SFP
Gi0/2 connected trunk full 1000 10/100/1000BaseTX SFP
Trunk Uplink Switch 1
Gi1/0/1 connected trunk full 1000 10/100/1000BaseTX
Trunk Uplink Switch 2
Gi1/0/2 connected trunk full 1000 10/100/1000BaseTX
Show int trunk from problematic switch
Port Mode Encapsulation Status Native vlan
Gi0/1 on 802.1q trunking 1
Gi0/2 on 802.1q trunking 1
Port Vlans allowed on trunk
Gi0/1 1-4094
Gi0/2 1-4094
Port Vlans allowed and active in management domain
Gi0/1 1,25-32,125-132,503,803-804,830,850-851,853,935,977,984-985,990,998-999,1001
Gi0/2 1,25-32,125-132,503,803-804,830,850-851,853,935,977,984-985,990,998-999,1001
Port Vlans in spanning tree forwarding state and not pruned
Gi0/1 1,25,27,29,31,125,127,129,131,503,851,853,935,977,985,999,1001
Gi0/2 26,28,30,32,126,128,130,132,830,850,984,990,998
Show int trunk from Switch 1
Port Mode Encapsulation Status Native vlan
Gi1/0/1 on 802.1q trunking 1
Gi1/0/2 on 802.1q trunking 1
Gi1/0/3 on 802.1q trunking 1
Gi1/0/4 on 802.1q trunking 1
Gi1/0/5 on 802.1q trunking 1
Gi1/0/6 on 802.1q trunking 1
Gi1/0/7 on 802.1q trunking 1
Gi1/0/25 on 802.1q trunking 1
Port Vlans allowed on trunk
Gi1/0/1 1-4094
Gi1/0/2 1-4094
Gi1/0/3 1-4094
Gi1/0/4 1-4094
Gi1/0/5 1-4094
Gi1/0/6 1-4094
Gi1/0/7 1-4094
Gi1/0/25 1-4094
Port Vlans allowed and active in management domain
Gi1/0/1 1,25-32,125-132,503,803-804,830,850-851,853,935,977,984-985,990,998-999,1001
Gi1/0/2 1,25-32,125-132,503,803-804,830,850-851,853,935,977,984-985,990,998-999,1001
Gi1/0/3 1,25-32,125-132,503,803-804,830,850-851,853,935,977,984-985,990,998-999,1001
Gi1/0/4 1,25-32,125-132,503,803-804,830,850-851,853,935,977,984-985,990,998-999,1001
Gi1/0/5 1,25-32,125-132,503,803-804,830,850-851,853,935,977,984-985,990,998-999,1001
Gi1/0/6 1,25-32,125-132,503,803-804,830,850-851,853,935,977,984-985,990,998-999,1001
Gi1/0/7 1,25-32,125-132,503,803-804,830,850-851,853,935,977,984-985,990,998-999,1001
Gi1/0/25 1,25-32,125-132,503,803-804,830,850-851,853,935,977,984-985,990,998-999,1001
Port Vlans in spanning tree forwarding state and not pruned
Gi1/0/1 1,851,853
Gi1/0/2 1
Gi1/0/3 1,851,853
Gi1/0/4 1,851,853
Gi1/0/5 1,851,853
Gi1/0/6 1,851,853
Gi1/0/7 1,851,853
Gi1/0/25 1,25-32,125-132,503,830,850-851,853,935,977,984-985,990,998-999,1001
Show int trunk from Switch 2
Port Mode Encapsulation Status Native vlan
Gi1/0/1 on 802.1q trunking 1
Gi1/0/2 on 802.1q trunking 1
Gi1/0/3 on 802.1q trunking 1
Gi1/0/4 on 802.1q trunking 1
Gi1/0/5 on 802.1q trunking 1
Gi1/0/6 on 802.1q trunking 1
Gi1/0/7 on 802.1q trunking 1
Gi1/0/25 on 802.1q trunking 1
Port Vlans allowed on trunk
Gi1/0/1 1-4094
Gi1/0/2 1-4094
Gi1/0/3 1-4094
Gi1/0/4 1-4094
Gi1/0/5 1-4094
Gi1/0/6 1-4094
Gi1/0/7 1-4094
Gi1/0/25 1-4094
Port Vlans allowed and active in management domain
Gi1/0/1 1,25-32,125-132,503,803-804,830,850-851,853,935,977,984-985,990,998-999,1001
Gi1/0/2 1,25-32,125-132,503,803-804,830,850-851,853,935,977,984-985,990,998-999,1001
Gi1/0/3 1,25-32,125-132,503,803-804,830,850-851,853,935,977,984-985,990,998-999,1001
Gi1/0/4 1,25-32,125-132,503,803-804,830,850-851,853,935,977,984-985,990,998-999,1001
Gi1/0/5 1,25-32,125-132,503,803-804,830,850-851,853,935,977,984-985,990,998-999,1001
Gi1/0/6 1,25-32,125-132,503,803-804,830,850-851,853,935,977,984-985,990,998-999,1001
Gi1/0/7 1,25-32,125-132,503,803-804,830,850-851,853,935,977,984-985,990,998-999,1001
Gi1/0/25 1,25-32,125-132,503,803-804,830,850-851,853,935,977,984-985,990,998-999,1001
Port Vlans in spanning tree forwarding state and not pruned
Gi1/0/1 1,26,126,850
Gi1/0/2 1,26,126
Gi1/0/3 1,26,126,850
Gi1/0/4 1,26,126,850
Gi1/0/5 1,26,126,850
Gi1/0/6 1,26,126,850
Gi1/0/7 1,26,126,850
Gi1/0/25 1,25-32,125-132,503,830,850-851,853,935,977,984-985,990,998-999,1001
01-22-2013 09:42 AM
Thanks for the additional information. So far it all looks reasonable (and looks like it should be working).
Perhaps you could post the output of show cdp neighbor from the problem switch and also from both of the upstream switches.
Where is the address 10.19.0.1 located? (on which device)
HTH
Rick
01-22-2013 09:46 AM
All looks ok
Not sure if this was done or can be done. But try to remove vlan 1 completely. Else default it's config shut it down and start configuring it from scratch - bring it up only when configured. Have had similar issues with svi's in the past
Regards
Sent from Cisco Technical Support iPhone App
01-22-2013 09:48 AM
Below is the cdp information you requested. 10.19.0.1 resides on the core switches via hrsp.
Problematic Switch
CHI-3560-2602#sh cdp neighbors gi0/1
Capability Codes: R - Router, T - Trans Bridge, B - Source Route Bridge
S - Switch, H - Host, I - IGMP, r - Repeater, P - Phone,
D - Remote, C - CVTA, M - Two-port Mac Relay
Device ID Local Intrfce Holdtme Capability Platform Port ID
CHI-3750G-2601 Gig 0/1 126 S I WS-C3750G Gig 1/0/2
CHI-3560-2602#sh cdp neighbors gi0/2
Capability Codes: R - Router, T - Trans Bridge, B - Source Route Bridge
S - Switch, H - Host, I - IGMP, r - Repeater, P - Phone,
D - Remote, C - CVTA, M - Two-port Mac Relay
Device ID Local Intrfce Holdtme Capability Platform Port ID
CHI-3750G-2602 Gig 0/2 131 S I WS-C3750G Gig 1/0/2
Trunk Switch 1
Capability Codes: R - Router, T - Trans Bridge, B - Source Route Bridge
S - Switch, H - Host, I - IGMP, r - Repeater, P - Phone
Device ID Local Intrfce Holdtme Capability Platform Port ID
CHI-3560-2601 Gig 1/0/1 173 S I WS-C3560-2Gig 0/1
Trunk Switch 2
CHI-3750G-2602#sh cdp neighbors gi1/0/2
Capability Codes: R - Router, T - Trans Bridge, B - Source Route Bridge
S - Switch, H - Host, I - IGMP, r - Repeater, P - Phone
Device ID Local Intrfce Holdtme Capability Platform Port ID
CHI-3560-2602 Gig 1/0/2 165 S I WS-C3560-2Gig 0/2
01-22-2013 09:58 AM
Perhaps we have a clue about the problem. I see that from the problem switch we believe that upstream switch 1 is using interface gi1/0/2
CHI-3750G-2601 Gig 0/1 126 S I WS-C3750G Gig 1/0/2
but on the upstream switch1 it think is it using interface Gig1/0/1
CHI-3560-2601 Gig 1/0/1 173 S I WS-C3560-2Gig 0/1
I am not sure what causes this mismatch. But I suspect that this is related to the problem.
HTH
Rick
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