Cisco Switching/Routing :: When Use Dot1q-tunnel On 3750 / Packets Seems To Be Corrupted

Nov 20, 2011

In fact i receive traffic on a one client per vlan basis (traffic is PPPoE), i receive all this traffic on a router, collecting all these vlan on a bridge where the pppoe packets are treated.When I use a transeiver to convert operator fiber arrival to my router copper media interface, i have no problem....
When I use dot1q-tunnel to make the same on my 3750, packets seems to be corrupted.I get PPPoE timeouts and packet loss, not regulary, totally stochastic...
I made dozen of tests and different settings, without success I first thougt of MTU issues. [code] I made tests with system MTU and/or system jumbo MTU above 1500, without success.I didn't found any known caveats on 3750 running Version 12.2(25r)SEE4 related to dot1q-tunnel.

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Cisco Switching/Routing :: LACP Over Dot1q Tunnel With 4506-E And IOS 15

Mar 14, 2013

i'm desperately trying to get LACP working over a dot1q Tunnel. The "Service Provider" Switches are two 4506-E Switches with SUP7-E connected via a 10G Link, running on cat4500e-universalk9.SPA.03.03.00.SG.151-1.SG
sample config:
dot1q tag vlan native
interface GigabitEthernet3/1
switchport access vlan 2001


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Cisco Switching/Routing :: Command To Debug Packets On 3750 Switch

Apr 18, 2012

What other command can be used to debug packets on a 3750 switch ?

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Cisco Switching/Routing :: 3750 Receiving CDP Packets From Switches Not Directly Connected

Jun 27, 2010

A specific switch port which happens to be part of a 2 switch 3750 Switch Stack is seeing multiple CDP packets from 3 extra switch port interfaces that are not directly connected. Noteworthy is that the far end devices have the correct CDP entries and I physically confirmed at least two of those connections that lead to the switch "upstream to the culprit switch". Tricky part is that its production so room for maneuvering is limited. At some point I disabled all Ports save for the real uplink and the problem momentarily disappeared. Re-enable the interfaces problem resurfaces. Is there an explanation, technique to eliminate the culprit with minimal disruption?

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Cisco Switching/Routing :: GRE Tunnel Alternatives For 3750?

Nov 22, 2011

I am looking for alternatives to GRE since it isnt officially supported on 3750's.  I am dealing with a Managed MPLS situation where the carrier manages the routers at each site and I only have read-only access.
The carrier is resistant to making any changes to the router since it would be a one-off or deviation from their standard config.  What I am trying to do is to force all site traffic for our department coming from different locations to be forced all the way back to corporate and not "see" any of the other departments.  I am not concerned about encrypting the traffic but finding a way to route the traffic back to corporate since I am pretty much not able to make any router changes.

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Cisco Switching/Routing :: Dot1q Tunneling On 2960C?

Apr 2, 2012

Is it possible to do dot1q-tunneling on the new Cisco Calalyst 2960 Compact series switches? I know that the 3560 series support it, but im unable to find any information about the 2960C series, personally i doubt it as the standard 2960 series don't support it.

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Cisco Switching/Routing :: 2960 / QoS Tagging And Dot1q Trunking?

Nov 9, 2011

If you have a router with multiple direct vanilla FE (non trunked) interfaces on a switch trying to send QOS tagged packets to a wifi bridge several switches away does the trunking in the switched infrastructure mess with the qos tags if no qos is configured on the switches.
Does it depend on the switch?  We have new 2960's running 12.2 and a few older 2950's running 12.1

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Cisco Switching/Routing :: Dot1q Encapsulation On 1721 Router?

Jan 26, 2012

enable dot1q encapsulation on two ethernet ports on a 1721 router.  I am able to configure it on the built in fastethernet port, but not on any interface provided by a WIC-1ENET or a WIC-4ESW.  I have an application that requires two physical ethernet ports that support dot1q encapsulation.

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Cisco Switching/Routing :: Cat4500e Dot1q Encapsulation Command Fails

Jul 17, 2012

I have a Catalyst 4500 L3 Switch Software (cat4500e UNIVERSAL-M), Version 03.02.00.XO RELEASE SOFTWARE (fc2). So I just wanted to verify that the switch only does dot1q encapsulation because the switchport trunk encapsulation dot1q command does not work.

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Cisco Switching/Routing :: Corrupted Memory 2811 Router

Jun 25, 2012

router 2811 has 2 files ios in flash
Router#sh fla
-#- --length-- -----date/time------ path
1     35202336 Mar 3 2008 16:12:28 +00:00 c2800nm-adventerprisek9-mz.124-8d.bin
13    59374168 Mar 5 2012 12:49:22 +00:00 c2800nm-adventerprisek9-mz.124-24.T.bin
151076864 bytes available (105431040 bytes used)
I try to make it load c2800nm-adventerprisek9-mz.124-24.T.bin
[Code] ...........
I did
verif flash:c2800nm-adventerprisek9-mz.124-24.T.binit is ok
is it corrupted memory? how to fix it?and aslo with System image file is "flash:c2800nm-adventerprisek9-mz.124-8d.bin"it dos not show voice ports for WIC2-FXO in runn conf

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Cisco Switching/Routing :: Switchport Trunk Encapsulation Dot1q Fails On A 4900m?

Jan 9, 2012

I'm setting up a new 4900m running  cat4500e-ipbase-mz.122-53.SG5.bin. I'm attempting to create Port-Channels as a Trunk for uplink to a 4503 running cat4500-ipbase-mz.122-37.SG1.bin.When I attempt the command "switchport trunk encapsulation dot1q" it errors out.

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Cisco Switching/Routing :: 4507 - Dot1q Encapsulation Option Not Showing Up Under Interface

Jun 9, 2012

I am trying to configure a 4507 R chassis with Dual SUP but i cannot see teh switchpot mode trunk encapsulation dot1q?
I have typed:
interface GigabitEthernet5/1
description DOWNLINK toxxxxxx
switchport mode trunk
channel-group 11 mode on
I have have searched all other commands and sub-commands but could only find dot1q-tunnel which I beleive is for QINQ or some QoS featues and lot for L2 encapsulations?
the puzzling is:
XXX-Core4507#sh int gi5/1 trunk
Port        Mode             Encapsulation  Status        Native vlan
Gi5/1       off              802.1q         notrnk-bndl   1
when I connect the dostribution switch a 3507 to this int gi 5/1, both interfaces do come up?

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Cisco Switching/Routing :: Recovering From Corrupted Software Router 2621xm?

Jan 14, 2013

I am trying to recover a corrupted ios, from rommon after configure all steps of IP_ADDRESS, TFTP_SERVER and so on, copy files correctly, but after it need router 5 minutes to erase flash, or something else....after it i can not boot from ios loaded as i show below:
File reception completed.
Copying file /c2600-advsecurityk9-mz.123-11.YZ2.bin to flash.
Erasing flash at 0x61fc0000
program flash location 0x60ea0000


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Cisco Switching/Routing :: 7604 WS-X6724-SFP - Can Apply Service Policy To Dot1q Main Port

Jul 9, 2012

Example config

int g2/24
service-policy output test
int g2/24.10
encap dot1q 10
ip address
service-policy output test

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Cisco VPN :: 4500 Switch - Dot1q Tunneling Via PPTP IPSec VPN Site-to-site Tunnel?

Nov 28, 2012

I have a situation where the site-to-site tunnel is already established using PPTP IPSec VPN with non Cisco Gateways terminating the link on each end. These non Cisco Gateways do not support L2TP tunneling, and there is no plan to change them.Beyond the Gateways on both ends, we have a Cisco 4500 series switch. We need to forward the 802.1q tagged VLANs between the two sites. Is it possible to use 802.1Q tunneling in this case, going via a PPTP tunnel ?
Cisco's setup uses dot1q-tunnel over a L2protocol-tunnel to preserve the original client VLAN tagging, so does this mean that the only option we have is to setup a L2TP tunnel at the Cisco device endpoints, and have that tunnel go through the existing PPTP tunnel (established between the 2 non Cisco VPN Gateways) ?

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Cisco VPN :: Srp527 VPN Tunnel Dropping Packets Intermittently

Dec 12, 2012

We have a Cisco ASA and recently purchased a cisco small business srp527 router.  It is connected to our ADSL2 connection and is working fine.  I have configured the device with an ipsec tunnel using an ike profile and the tunnel is created successfully with packets traversing the tunnel.  However packets are being dropped intermittently, with no cause.  The link is currently not being utilised, there is no load on the network however when I ping Google and any address subject to the rules of the tunnel i notice that a single packet is dropped every now and then.

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Cisco WAN :: 1841 - Duplicate Multicast Packets With DMVPN Tunnel

Mar 21, 2013

I have a setup where a spoke (cisco 1841) is sending a multicast feed to a hub (cisco 2951) via a DMVPN tunnel on the Internet. The feed arrives on interface fa0/0 of the cisco 1841 and is forwarded to the tunnel interface.  It is about 160,000 kbit/s and 18 pps. This always looks the same:
cisco2951-1-hub#sh run int tu10
interface Tunnel10
description DMVPN TUNNEL


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Cisco Switching/Routing :: Perform STFTP On 3750 Or 3750-X?

Jun 30, 2012

Do I need the Universal image to perform stftp on a 3750 or 3750-X?

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Cisco Switching/Routing :: Why C2960 Is Dropping Packets

Dec 26, 2012

We have a customer who uses about 20 x c2960's switches for access layer and 2 x c3560e for distribution layer. C2960's uses C2960-LANLITEK9-M , Version 12.2(58)SE1. Everything was working fine. Now we got information, that sometimes there are problems with connectivity. Customer tries to reach internet.
SW11#sh int fa0/18       
FastEthernet0/18 is up, line protocol is up (connected)
Hardware is Fast Ethernet, address is e8ba.806a.4412 (bia e8ba.806a.4412)


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Cisco Switching/Routing :: Ignored And Overrun Packets On 7204VXR?

Feb 21, 2012

I am seeing packets being ignored on GigabitEthernet0/0, but can't find any reason what the reason can be for that. So far calculated that about 3% of the traffic is being ignored. If it was caused by shortage of input buffers, I would expect to see increasing counters somewhere at no_buffer, but that is not the case. The average txload and rxload on the router is low all times.

#sh int g0/0GigabitEthernet0/0 is up, line protocol is up  Hardware is i82543 (Livengood), address is 0012.7f8a.8008 (bia 0012.7f8a.8008)  Description: ;Link to NORISMP998 G5/2  Internet address is  MTU 1500 bytes, BW 1000000 Kbit, DLY 10 usec,     reliability 255/255, txload 2/255, rxload 2/255  Encapsulation ARPA, loopback not set  Keepalive set (10 sec)  Full-duplex, 1000Mb/s, link type is autonegotiation, media type is SX  output flow-control is XON, input flow-control is XON  ARP type: ARPA, ARP Timeout 04:00:00  Last input 00:00:00, output 00:00:00, output hang never  Last clearing of "show interface" counters 8w2d  Input queue: 0/75/522186/1117 (size/max/drops/flushes); Total output drops: 0  Queueing strategy: fifo  Output queue: 0/40 (size/max)  5 minute input rate 11667000 bits/sec, 2319 packets/sec  5 minute output rate 9377000


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Cisco Switching/Routing :: 3750x 24s Not Forwarding Packets

Mar 1, 2013

We have a 3750x 24s acting as a root switch for about 10 other 3750x's. Everything else seems fine, but the device stopped forwarding packets to the applied static route. [code]

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Cisco Switching/Routing :: 7200 - Netflow / Packets Not Sent?

Jul 23, 2012

router 7200 (12.2(33)SRE1)
two interfaces with traffic going through, placed in a Data-VRF
Another physical interface and loopback interface in the global routing-table.
ip flow ingress on all physical interfaces configured
It was running for at least a year: I was getting netflow packets on my analyzer from the box. Since a couple of weeks I get no netflow-packets anymore.debug ip flow export  tells me "IPFLOW: Sending export pak to ... port 2055"
But the packet is not leaving the box. By setting up an ip sla monitor udp-echo I simulated some traffic (udp/2055) which is leaving the box.


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Cisco Switching/Routing :: C3750 - Packets Lost

Nov 21, 2011

I have a stack of 2 C3750-switches (WS-C3750G-24TS-1U) with IPBASE-firmware (12.2(52)SE). 
When I ping to a machine (in this case a virtual one), the replies are always received on the port where the machine is connected, but on the port-channel connecting to the stack of the 'pinging device' the reply comes only for certain initiators, and not for all.
Gi1/0/6: Device/Server I want to connect too ; defined as access port
Gi1/0/25 + Gi2/0/25, as Port-Channel 1: The location of the devices I connect (read as: the uplink to the stack of the PC's), defined for Dot1Q-trunking
Monitoring setup: Source ports: Both: Gi 1/0/6, Po1 (or Po1 replaced by both interfaces)
For the machines which can ping the server I see 2 echo (ping) requests, followed by 2 echo (ping) replies ... So once seen on the Po1, and once seen on the interface Gi1/0/6.

However for other machines, the 2nd reply is missing ; which must be caused by the dropping of these packets in the switch.  At least, I my opinion this must be the reason... But I can't see any (change of) output drops at int Po1, nor at Gi1/0/6.  The CPU doesn't seem to have high usage, and even then, I don't think the error would be constant, as it's always failing for some PC's, and never for others... (at least for a certain time, a few hours it can be constant, the problem dissapears from time to time).

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Cisco Switching/Routing :: To Use DFC3 6500 For Forwarding Packets

May 31, 2012

From everything I read it seems like DFC is for forwarding packets.  When I hear packets I think of layer3.  If my 6500s are just being used as a big layer2 only switch do I need a DFC?  I am being told the 6500 looks at the layer 2 frame and the layer 3 patch header information before forwarding the frame.  How true is this?

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Cisco Switching/Routing :: C6500 Packets Don't Get Hardware Switches

Oct 23, 2011

My C6500 is having relatively high CPU (no spikes, but constantly)
I'm under the impression that cef is causing this problem because alot of packets are being processed or send to/from the CPU. [code]

I did a netdr and I can see that the majority of packets going to the CPU are packets for which I have an entry in the CEF table.What can be a reason why those packets don't get hardware switches?I'm running Version 12.2(33)SXH5 - Sup720-10G.

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Cisco Switching/Routing :: SG300 - Session Starts With Two SYN ACK Packets?

Apr 20, 2012

I am having trouble with my Cisco SG300 switch big time. I have two servers with IP addresses and sitting on the same switch which is a Cisco SG300. I initiate a file transfer from to I could see lots of Dup Acks and retransmissions which means something is wrong in the connection. Further, I could see the session initiation a bit bizarre. I could see two SYN packets sent from to and also two SYN ACK packets returned by The switch forms part of a network but since both the servers are sitting on the same switch I suppose the rest of the network doesn't come into play when one server talks to the other.
See also the number of Dup Acks and retransmissions. The two switch ports connecting the servers have speed and duplex set to auto negotiate, flow control is enabled. What could cause this sort of problem?Could it be any setting on the switch or the servers' NICs?Or could it be a bad switch that causes this?

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Cisco Switching/Routing :: 6500 Unexpected Packets On Port

Apr 17, 2012

i have several cisco 6500 switches, and user switched connected to my example i have a global service vlan, where some access ports are directly connected on the 6500, and this vlan is also allowed on the trunks to the access switch.
now i am connected with ma laptop on a access switch, where my port is in the same vlan. when i do a show mac address-table on my access port, i can see my own mac-address, nothing else.when i start wireshark to see the traffic, all i should see is traffic from or to my MAC, or broadcasts/multicasts.
But i can see other unicast traffic with different source/destination mac than mine.It seem slike these packets get broadcasted over the whole VLAN, but its no broadcast MAC nor IP.

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Cisco Switching/Routing :: C3825 ISR IP Inspect Dropped Packets?

Oct 31, 2011

i am wanting to log dropped and oop packets on a c3825 isr with ios12.3(11)T3.  on other routers(like a 2951 running 151-4.M2)i can state ip inspect log drop-pkt and it will log to buffer or syslog all dropped and oop packets.  can i do this on this 3825 another way

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Cisco Switching/Routing :: Nexus 5000 Jumbo Packets?

Oct 7, 2012

on some of our ports on Nexu 5000 and on the connected FEX we can see a lot of Jumbo Packets though there is not enableed any JumboFrame on the Switch, all Interface and system MTU is set to 1500.
DBE-LINZ-XX41# sh int Eth113/1/27
Ethernet113/1/27 is up
Hardware: 100/1000 Ethernet, address: d0d0.fd1b.b69c (bia d0d0.fd1b.b69c)


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Cisco LAN :: 3750 How To Filter DHCP Packets From / To Server

Dec 27, 2011

a power analyzer in my network is sending some packets that are unexpected and incorrectly recognized as DHCPOFFERS. As a workaround, I would like to filter those packets with my Cisco switch 3750.Suppose IP_POWER_ANALYZER is the ip address, what could be the best choice

1. deny udp any IP_POWER_ANALYZER eq bootpc
2. deny udp any IP_POWER_ANALYZER eq bootpc; deny udp IP_POWER_ANALYZER any eq bootps
3. deny udp any eq bootpc IP_POWER_ANALYZER eq bootps

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Cisco Switching/Routing :: Forwarding IEEE 802.3 Raw Packets Through 2960G Switch

Dec 5, 2011

I have a requirement to monitor downstream data feed from a remote site and feed it to multiple destination devices for recording.  The source data will be fed into a port on a Cisco 2960G switch then, using the monitor function, be forwarded to multiple interfaces.   This works fine for normal Etherent II traffic.  We tried a test using a device that generates IEEE 802.3 Raw packets ('type' field is used as a 'length' field) but found that while the traffic appeared to be accepted by the input port with no errors it was not forwarded to the destination ports, even when using the monitor function.  I did try the 'encapsulation replicate' feature with no luck.  It does not forward these packets even if I set all the ports into a common VLAN and let the switch just perform a normal switch function (non monitor).
if it is possible to get the IEEE 802.3 raw packets to pass through the switch and if it is, how to or what I need to do to make it work?

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Cisco Switching/Routing :: Jumbo 9000 Packets Configured But Not Working?

Feb 23, 2012

I have a switch that I have configured for jumbo packets, but they don't seem to be functioning. I have set system mtu jumbo 9000. The hosts are connected via 2x EtherChannel links. The hosts are jumbo frame enabled, and can ping their own local address using jumbo packets & do-not-fragment flags on the pings. They cannot, however, ping each other or the switch that way - it always says that the packet requires fragmentation. I know the attached machines (they're all VMs) and virtual switches support jumbos because I can ping within the virtual interfaces of the VMs. It's just traffic that goes over the switch that fragments.The switch is a WS-2960G-48TC. Here are the various outputs, with a section of config at the end.
hrnacancwtdevs3#show system mtu 
System MTU size is 1500 bytes
System Jumbo MTU size is 9000 bytes
System Alternate MTU size is 1500 bytes
Routing MTU size is 1500 bytes


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Cisco Switching/Routing :: SG-300 52 Native VLAN Blocking Network Packets

Jun 15, 2013

SG-300 52 native VLAN blocking network packets

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