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 :: 3750X Switches Dropping Packets On Uplink Interface?

May 9, 2013

We have a remote site that is using 3750X switches as layer 2 switches back to our home site.  The uplink port is showing dropped packets but the utilization on the link is never about 10%.  We have a 100Mb circuit to this site.  Our speed tests and iperf tests are not showing any issues that we can see.  However the port is still droping packets.  It is not dropping at a high rate but they are dropping.          
switch#sh platform port-asic stats drop gi1/1/4
  Interface Gi1/1/4 TxQueue Drop Statistics    Queue 0      Weight 0 Frames 0      Weight 1 Frames 0      Weight 2 Frames 0    Queue 1      Weight 0 Frames 52876      Weight 1 Frames 2      Weight 2 Frames 0    Queue 2      Weight 0 Frames 0      Weight 1 Frames 0      Weight 2 Frames 0    Queue 3      Weight 0 Frames 0      Weight 1 Frames 0      Weight 2 Frames 1330874    Queue 4      Weight 0 Frames 0      Weight 1 Frames 0      Weight 2 Frames 0    Queue 5      Weight 0 Frames 0      Weight 1 Frames 0      Weight 2 Frames 0    Queue 6      Weight 0 Frames 0      Weight 1 Frames 0      Weight 2 Frames 0    Queue 7      Weight 0 Frames 0      Weight 1 Frames 0      Weight 2 Frames 0switch#
Is there a way to capture these dropped packets to see what they are?  We do have VOIP phones at the site and are using Qos.

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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 :: C6500 / MPLS Campus LAN Virtualization And VSS?

Apr 21, 2010

I'm going to start the evaluation of implementing the virtualization of our campus LAN using MPLS.We'll get many inter-VLAN routing domains per VRF on the same LAN infrastructure.The LAN infrastructure is based on C6500 implementing VSS.Do you have experience with this kind of setup?Any known/faced issue that might prevent the setup of MPLS on VSS enabled C6500?

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Cisco Switching/Routing :: C6500 - Heat Dissipation With Or Without Transceivers?

Apr 13, 2013

how is calculated heat dissipation of ethernet modules for c6500? For example, heat dissipation of WS-X6908-10G-2T - 2083.32 BTU/hour.. This heat dissipation of the empty module, without transceivers? Or including all installed transceivers?

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Cisco Switching/Routing :: C6500 QoS - Link Between Internal DSCP And CoS Value

Sep 6, 2012

there is something I find strange on C6500 about QoS: C6500 derive an internal DSCP value for it's internal use, but when configuring the qos mapping on output interfaces, only a cos  value (I guess, an internal cos value) can be used. Is it a misunderstanding from me, or is it really illogic?

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Cisco Switching/Routing :: How To Configure IP Cache Flow On C6500

Nov 28, 2012

I want to see net flow data.I have configured this command on the c6500.but I can to see data only below...How can I configration ip cache flow on the C6500? what is the problem?
int gi4/31
ip add x.x.x.x
ip route-cache flow 
c6500# show ip cache flow
Displaying software-switched flow entries on the MSFC in Module 5:


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Cisco Switching/Routing :: C6500 Bootdisk And Supervisor Engine

Apr 5, 2013

For C6500 chassis,  sup-fould like to know the dirrerence between supervisor engiene 720 sup-bootflash and sup-bootdisk?

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Cisco Switching/Routing :: C6500 / SNMP-server Traps For ISDN?

May 17, 2012

Trying to migrate the config run on IOS 12.1 to 12.2 ?It seems there's no snmop traps isdn command support on 12.2.
where i can enable trap on ISDN over IOS 12.2 (33) sxj1 running on C6500 chassis?

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Cisco Switching/Routing :: C6500 Filter ARP Answer On 802.1q Port For Specific VLan

Oct 10, 2012

I am trying to filter ARP answer arriving on a C6500 trunk port, for a specific vlan.Filtering conditions are:

- packet arrive from vlan ID x on the trunk (on only for this vlan ID)
- source MAC address = xx:xx:xx:xx:xx:xx

Thae aim is that the C6500 with never enter into its CAM table this MAC address.I looked at several methos like service policy or vlan filter, but no solution for the moment.

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Cisco WAN :: C6500 Routing One IP Away From Connected Sub-net

Jan 24, 2013

I have lets say a /24 directly connected via a vlan on a C6500 in the network.I'm trying to migrate some servers/devices away from it , however I need to move parts of it away bit by bit ( For example a /32 or a /30  that make up the /24 )Ive tried a direct ip route x.x.x.x y.y.y.y     and even a ip route x.x.x.x y.y.y.y 1
Yet it still prefers the directly connected range ( as I pretty much expected. )
Is there any way I get it to prefer a static route over a directly connected?

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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 :: 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 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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Cisco Switching/Routing :: NetFlow / 6500 / Export Packets Were Dropped Due To No Fib?

Mar 13, 2012

I have a problem with the 6500 not exporting netflow data. They are not exported due to no fib.I have read somewhere that this has something to do with VRF. VRF are running on the router.ip flow ingress has been applied to desired ip int.Is there anything I could do to make it export netflow data?
VSS-core-XXX-rs1#sh ip flow export
Flow export v5 is enabled for main cache
  Export source and destination details :
  VRF ID : Default
    Source(1) (Unknown)


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Cisco Switching/Routing :: Catalyst 2960 Drops Packets After Enabling QoS

Nov 4, 2011

why the QoS deployment causes ports on 2960 switches to drop packets although there is no bandwidth contension? (output bit/second of the interface)packet drops at threshold 1, queue 2 ( queue 3 in config)
We are using Catalyst 2960 switches and are experiencing issues with QoS. After the QoS, we experience a lot of packet drops and it make the network slow. It appears that the slow performance relates to the egress queuing of each port.
Cisco IOS Software, C2960 Software (C2960-LANBASEK9-M), Version 12.2(50)SE5
switch_06#show inter fa0/1 | in drops|queue|output
input flow-control is off, output flow-control is unsupported
Last input never, output 00:00:01, output hang never


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Cisco Switching/Routing :: WS-C3560CG-8TC-S / Speed Reduced And Drop Packets With QoS?

Apr 11, 2012

I put a QoS in a  WS-C3560CG-8TC-S  version 12.2(55)EX2.  in our lab file upload or download speed much reduced and drop the packets with QoS everyting is fine without QoS
Here is the config: My question is why I speed reduced a lot and packets to be dropped with QoS.everything is fine WITHOUT QoS.

class-map match-any VoIP  description Voice IP Phone RTPmatch access-group 157
class-map match-any WEB  description Internal Web, SSL Web, DNS query, Pinnaclematch access-group 153
policy-map QOSMARK
class VoIP  set dscp ef
 class WEB  set dscp cs3


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Cisco Switching/Routing :: 1811W - Packets Not Getting Encrypt And Decrypt IPSEC

Dec 14, 2012

I have 2691 Router conencted to Internet and it is doing Nat. This connects to 3550A  Switch which has connection to 1811W  Router.
I setup VPN between 1811W and 3550A. 3550A has connection to 2691 via ospf.
OSPF is running between 1811w and 3550A.
1811w# sh crypto isakmp sa


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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 :: 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 :: Block All DHCP Packets Through 2960S LAN Base IOS?

Mar 23, 2013

I am trying to block all dhcp packets through 2960S lan base IOS. But when i set no trust interface for dhcp snooping, the dhcp packet source port will be err-disabled.  Is there any other solution to block any DHCP packet through switch without interface or other service outage?Is possible to block DHCP packet through specific VLAN?

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Cisco Switching/Routing :: Catalyst 4948 Drops Truncated Packets?

Jan 4, 2012

I'm using a Catalyst 4948. It seems to drop all truncated packets. I don't know whether this is an expected behavior.I'm developing a program which processes packets in the following steps:

1) capture packets
2) if a packet is too long, truncate it to a certain length
3) insert a vlan tag (say 100) to each packet
4) send them to the switch
Mac address learning is disabled on the vlan 100, so the packets should be seen at all ports of the vlan. However, I only observed untruncated packets. Truncated packets seemed to be dropped by the switch.The summary of the source port is:
c4948-01#show interfaces gigabitEthernet 1/22 summary
Interface               IHQ   IQD  OHQ   OQD  RXBS RXPS  TXBS TXPS TRTL
* GigabitEthernet1/22      0     0    0     0 4018000  7390  2000    3    0
The receiving speed was approximately equal to what I sent.The summary of another vlan 100 port is:
c4948-01#show interfaces gigabitEthernet 1/18 summary
Interface               IHQ   IQD  OHQ   OQD  RXBS RXPS  TXBS TXPS TRTL
* GigabitEthernet1/18      0     0    0     0     0    0  3000    4    0
Almost no packets were output.I see a Cisco document says "ingress port drops corrupted packets" [URL] then my questions are:
1) Is this the root cause of dropping truncated packets?

2) What criteria does a switch use to check corrupted packets? My understanding is that truncated packets could have wrong L3 and L4 data, but they can't be detected at L2.

3) If switch drops mal-format packets, can we disable this feature?

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Cisco Switching/Routing :: EHWIC-1GE-SFP-CU MPLS Labeled Packets Are Not Being Processed

Dec 27, 2011

We have the problem that MPLS labeled packets are not being processed on EHWIC-1GE-SFP-CU if L3PDU + Shim-Header exceeds 1500 bytes.When we move the config exactly to the on-board Interface Gi0/0 it works with put any problems. [code]

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