3750 - Sporadic Network Blips
Jun 28, 2013
I have a 3750 acting as the DSW, with a few 2960's (asw's) attached to it going to different buildings.
One building has been complaining of random 15 second to 1 minute outages. Its rare though. Happens anywhere from once per week to maybe 4 times per week. The times of the day it happens is random also.
I've had them ping the gateway when it happens, and the ping fails for a few seconds then starts to work.
One of them ran a continuous packet sniff, and sent it to me after it happened. Nothing weird going on in the sniff, except for the obvious failure of getting traffic. When it happens I see a crap ton of arp requests to the gateway, which makes sense I suppose since the hosts can't get past the gateway anymore.
They've replaced the fiber to LIU, the sfp, and then even the 2960. Its updated to latest code.
I'm guessing the problem is at the 3750. We havent touched it yet. CPU/memory looks fine (when checking the history). No input/output errors on any interface. Logs don't show anything, not even a flapping interface. But we are always looking at this after the fact, since by the time they email or call us, it has already passed...
Other buildings that are fed from this 3750 haven't complained though, so I'm not sure if they are experiencing problems or not.
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Aug 16, 2011
I play some games online casually, primarily League of Legends, and about every second sitting the internet has frequent 'blips' of going down for long enough to make the game have connection issues. I've noticed it is the sending that goes down and if the receiving goes down at all, then it is very quick. (The game still plays and I see everything that is happening but cannot respond. This happens in Rift too the rare time I play it and the even rarer flash games I play). Though I have tried many things to fix this issue, it hasn't truly bothered me that much until recently when I realized I play even less than I normally would out of fear the game session will be ruined by the internet.About half a year ago the internet was in very bad shape. It crashed often and stayed down for a long time. My ISP is Comcast (Or Xfinity...), and it took me many weeks of harassing their customer support (off and on) for them to fix it. Then it ran smoothly for a couple months before it started having these blips.
The details:When it has a blip, before, during, and afterwards (I've sat by the modem to watch it happen), there is no indication of the internet having trouble on the modem indicator lights. Nothing changes, and they flash at about the same rate as normal. The router I have is a Linksys, and nothing seems to change on it either during a blip.I have the games port forwarded. All my firewalls including the windows firewall are off. I have updated my wifi and internet drivers on my computer and am using the firmware recommended to me by my ISP for the router.
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Nov 4, 2012
Ive been running my computer on our home wireless internet connection with almost no problems, but about two weeks ago our internet went down and after it went back up a day later i had very slow internet speed and a very sporadic connectivity (random disconnects, dns timeouts etc) I used to get speeds up to 20-22 mbps but now i can barely push 4mbps, the other computers on our network has fine connectivity its only my stationary computer that has these issues
Microsoft Windows [Version 6.1.7601]
Copyright (c) 2009 Microsoft Corporation. Med ensamr�tt.
C:UsersGreattech>ipconf /all
ipconf �r inte ett internt kommando, externt kommando,
program eller kommandofil.[code]......
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Feb 8, 2013
I just bought a linksys 4200v2 router and I still get disconnects every so often.... usually disconnects for about 30 secs then comes back online. When it disconnects, it disconnects all devices on the wireless network router... laptops, iphones, etc..I have tried adjusting some settings in the router but I simply don't know enough to know what I'm doing
Network mode: Mixed (same as 5ghz)
SSID: different from 5ghz
Security Mode: WPA2/ WPA Mixed Mode (same as 5ghz)
Channel Width: 20 mhz only (40 for 5ghz)
Channel: 1 (auto for 5ghz)
SSID Broadcast: yes (same for 5ghz)
How can I stop being disconnected from the internet? I have inssider and I checked to see what channel my neighbors are using and all of them are using 6 or 11 so I decided to use channel 1 for 2.4 ghz.I have a ~3000 sq ft home with 3 levels (basement, first, second). We do some work in the basement and second floor... most is done on the first.
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Feb 19, 2011
Here's my situation.I had an 8 year old desktop computer that I just replaced with a brand new one (Lenovo). Prior to replacing it, I assumed the slowness and occasional inability to connect to the internet were caused by the computer being so old. But once I replaced the computer I still had problems - in fact it was worse.
At that point I was reminded that the modem was also 8 years old so I had the cable company replace it (Scientific Atlantic Model DPC2203C). The connection improved for a few days but then it went right back to how it was.
I have a wireless router (Cisco Linksys Model WRT160N V2), which is hooked up properly. When I got the new modem I had to reset the router. My wife's laptop now sometimes has connection problems which it never had before, and on my (work) laptop I can access the wireless connection but not through the same entryway that I had before. I'm providing this information because I think it may be relevant. It seems like something has to be up with the wireless router since I reset it. Another thought is that possibly the problem is with one of the wires between the router and either the modem or the computer - not sure if the sporadic connection problems is an indicator of that.
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Jul 11, 2012
Recently I upgraded the wireless infrastructure in my campus and deployed WISM2 controllers and Cisco 3502i APs throughout the campus. Until now all my users were using 802.11b/g/a speeds without any issues. However, now I am trying to enable 802.11n speeds in a test group of users by enabling AES encryption and I am seeing lot of issues. These test users sporadically loose wifi connection and an asterix appears in the WIFI icon in the task bar. Interesting part is that all the manually configured wireless networks in the laptop stop displaying. The broadcasted SSIDs continue to show up though. All these users are using "Intel(R) Centrino(R) Advanced-N 6200 AGN" wireless cards with driver version 13.3.0.24. I had upgraded one of the client drivers to the latest 15.1 version. However, he still complained about wireless disconnection (I am not sure about this problem as I didnt personally attend his laptop to know the cause of diconnect).
One another interesting incident is that 2 people from this test group were having a meeting in a conference room once and surprisingly both dropped at the same time with the same symptoms. The only fix was to reboot their PCs.
I have done following changes in my controllers hoping that the problem would get fixed, But still no luck.
1. Enabled client band select.
2. Checked EDRRM for A as well as B/G
3. Changed Channel allocation from freeze to auto.
4. Enabled "avoid persistent interferers".
In my calls with Cisco support we also ran debugs in the controller and sniffer captures in the client machine. All we see in the controller is that the client dropped without any reasons. Also, didnt find anything significant in the sniffer captures. At this point not sure what to do. If upgrading the client driver is an option, then I need to produce some proof or document to the management which says the current 13.3.0.24 has known bugs to run 802.11n speeds. Scanned the entire internet, put a post in intel support site but no luck.
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Jul 11, 2011
I have a office that was converted from a older townhouse. The building has 3 floors with the distant of each floor expands no more than about 60 - 75 feet from end to end of the building. Not sure what's in the walls as the building is at least 20-25 years old. Total number of users is about 20 - 25.
Here is the problem..
I have a WRT54G wireless router setup to provide wireless coverage for this office, located on the 2nd floor, For some reason, about 10 - 15 feet from the opposite end of the building, the signal drops off big time. Regardless of the floor. So to assist with the signal, I installed a wireless 300N Gain extender on the same floor on the opposite end of the building where the signal was weak. At first, it seemed to work by boosting the signal, but then it seems to show the same issue as before.. sporatic signal loss, signal fluctuation, etc.
My question is should I replace the wireless booster with multiple wireless APs located throughout each floor... maybe 1 per floor? If so, is there a trick to configuring all 3 APs to have the same SSID and same encryptionsso it will be seamless to the users? Since the first AP works fine, I wanted to get 2 additional WRT54G units.
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Sep 22, 2009
We have about 20 of the above WAPs in our company network and are quite satisfied with the performance.However occasionally we need to manually reboot the WAPs in order to resolve sporadic connectivity issues that cannot be resolved on the client devices. In order to optimize the performance we would like to automatically restart our WAPs at a certain time (e.g. at night) on a daily or weekly basis.We are currently using WAP4410N-fw-2.0.0.5-K9.
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May 20, 2012
I am considering running stacked 3750 L3 switches as the edge of the network, which will connect to the ISP. The ISP would hand off two lines with one to each switch and two lines to each client zone. Does running HSRP, running port channels, or running routing protocols seem like the best option for redundancy?
Lastly, will the 3750 provide all the QoS I should need for restricting each client zone's bandwidth both up and down? Could I get away with a lower model and still get these features?
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Mar 25, 2013
I am considering running stacked 3750 L3 switches as the edge of the network, which will connect to the ISP. The ISP would hand off two lines with one to each switch and two lines to each client zone. Does running HSRP, running port channels, or running routing protocols seem like the best option for redundancy?
Lastly, will the 3750 provide all the QoS I should need for restricting each client zone's bandwidth both up and down? Could I get away with a lower model and still get these features?
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Jun 30, 2012
Do I need the Universal image to perform stftp on a 3750 or 3750-X?
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May 21, 2012
we have three separated network segments going to one Cisco 3750 switch all is L2 .. from this switch is 100 mbit uplink.we need to apply some Qos mechanism not to saturate line by traffic from one network.. Configuration from various reason CANNOT be done on switch where 100Mbit line is terminated.. so all must be done on SW1,2,3..Correct me if iam wrond but as switches doesnt see traffic from other network iam affraid only think we can do is limit bandwidth on links going into SW1,2,3 to 33 Mbit.I found commad srr-queue bandwidth limit.But links going to SWs are 1Gbit so if i force bandwidth to 10% (minimum what command allows) its 100 Mbit..If I force speed on those links to 100Mbit and than apply srr-queue bandwidth limit to 30% doest it work.??. Will srr-queue bandwidth limit speed to 30Mbit?? Or srr-queue bandwidth limit is calculated from maxim speed of interface?
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Feb 13, 2012
Currently we have an Ava ya IP Office switch running on the same network as our PC clients. I would like to seperate the two network into 2 V LAN's.
We have a mixture of Catalyst 3750 switches and some older 3500 models.Where do I start? Should I leave the PC's and servers on the default V LAN and just move the IP handsets?
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Aug 22, 2011
I would like to push route for admin services (Vlan20) to bypass the firewall via an other connection (CSI to CSE). So my first choice was to create a route-map in (CSI) but I don't know how to do it. On my Firewall ASA, I don't have any Context License, that is why I would like to do it like this.
I have included some part of my initial configuration CSI and CSE and diagram.
CSI configuration (Switch L3 3750) {
interface GigabitEthernet1/0/1
description To ASA
no switchport
[Code]....
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Oct 18, 2012
For the c3kx-nm-1g network module it looks like it will take the standard sfp's for fiber but I need copper rj45 connections, is there a copper sfp for this?
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Apr 2, 2012
why Windows Server 2008 is not a supported OS for Cisco Network Assistant?I am currently evaluating switch management solutions for use with Catalyst 2960 and 3750 series switches, and would like to be able to backup and restore configurations, as well as make configuration changes. My management Server is running Server 2008.Is Prime LMS my only option?
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Apr 18, 2012
I am working at a client site today on a routing issue. I am currently working on an issue where a 3750 switch running EIGRP will not update its neighbor router when a network statement is added to the eigrp instance.The neighbor is a 3825 router.
Both the switch and the router have a common network which is 192.168.36.0/24.
Both the switch and the router are in a neighbor adjacency.
Both boxes have "no auto-summ" in the routing configuration instance.
I can run debugs on both routers (debug eigrp packets) and then I can watch queries and updates when I issue "auto-summ" or "no auto-summ". Also I see a "graceful restart" for the peers when this is done.I had an expectation that when I added the network (this is just an arbitrary network for testing, which is 172.16.69.0/24). I wanted to watch this network being sent in an update to the neighbor router.When I add the above mentioned network, there are no updates packets sent from the 3750 to the 3845. I have not had success to this point trying to resolve. I have followed the Cisco document "Troubleshooting EIGRP Flow Chart", but have exhausted all it has to offer and now it is at the point where it is telling me to contact TAC.
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Jan 25, 2011
I am just browsing and looking for a solution to converge my multi-vendor switched network and bring some redundancy to it as recently
we managed to get a redundant links. I have a need to change core switch to Cat3750G, which has Per-V LAN-RSTP+ on board, but tests have shown that it won't be compatible with some other proprietary per-V LAN RSTP solution other vendor's switches use currently.
So, I thought maybe standard-based MSTP design might do the trick. I've made some tests and got some weird and unstable switching result. I have two topology rings with a core switch in the center. Every ring has about 10 switches, so practically network diameter may vary from 5 switches (when spanning-tree converges in the center and I have a blocking port somewhere int the middle of the ring) to about 10-11 switches (if a I have link failure on any of ports right at the core switch). I disconnected one port from core switch to eliminate a possible switching loop while I will be configuring new MSTP design. Then I started enabling MSTP on all the switches staring from core Cat3750G to MSTP, one by one, placing all switches to the same MSTP region, and placing all V LAN's to default MSTI0(CIST) cause I don't need to organize any separate MSTP instances for every V LAN or for group of V LAN s. When I turned MSTP on on 7th or 8th switch in the chain (cause I had a physical chain when I disconnected one port out of redundant ring) I got all switches "flapping", storming and flooding the network with broadcasts. Even when I had one redundant port disabled.
I have no idea what I am doing wrong. I noticed that Cat3750G has an option that defines a possible network diameter which actually automatically changes some hello, max age etc. attributes according to diameter specified. When I defined a maximum network diameter of 7, if didn't change anything: I still have hello timer of 2 sec etc. I've been wondering if the maximum network diameter has something more than just a "variable" to fine tune hello timers etc? Maybe I won't be able to use MSTP in my network which might have diameter more that 7 switches. Or maybe it was a mistake of placing all the switches to the same region and all the v LAN s to the default MSTI0 (CIST) and I should configure one MSTI per V LAN or per some group of V LANs and subdivide my switches to few MSTP regions?
My topology briefly looks like this:
+--SW1----SW2----SW3---CORE---SW4---SW5--SW6---+
| | | |
+---SWxx---SWxx-----------+ +------SWxx-----SWxx----+
As I said, each "ring" has about 10 switches connected side by side.
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Feb 2, 2013
I am planning to upgrade the current core switch(3750) to 6509 series switch. Since we have a production network running we have to plan for an online core switch upgrade.
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Oct 10, 2011
I'm looking at adding a Cisco 3750-X switch running c3750e-universalk9-mz.122-55.SE1 (IP base license) into a stack of 3750-G switches running c3750-ipbasek9-mz.122-55.SE1.bin Given that the version and feature sets are the same I don't forsee any compatibility issues. Would there be any reason why a universal image wouldn't stack correctly with other switches running the single .bin file?
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May 21, 2012
We have a stack of switches that is at the max number of members allowed in the stack. Problem is we are running out of port density and need to add more ports. So instead of adding a whole new stack I would rather replace 2 of the 24-port swicthes with 48-port switches.
If the two 24-port swicthes we are removing are stack members and neither of them are the stack master, I should be able to replace the 24-port switches with the 48-port switches without bringing the master offline? If the new 48-port switches are running the same IOS version as the current 24-port swicthes, they should add themselves to the stack?Would I have to tell the new 48-port swicthes what switch numbers they are replacing in order for them to be added to the stack since we are at the max number of members?Also since the 48-port swicthes are replacing 24-port switches will the master give the 48-port switches the configuration for only the 24-ports?
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Feb 16, 2012
I have a cisco 3750 switch and i given 2vlans (40, 118). 40 is local and 118 is public.I given the public ip for vlan 118. now i am able to telnet from same vlan (118 only) but i am not able to ping and telnet as globally. [code]
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Nov 10, 2012
I have a 3750 switch.The status of the switch is rommon," switch : ".there is not an IOS in the switch....Are there ways to install an IOS excepted xmodem
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Oct 31, 2011
Trying to apply NTP authentication to 3750 switches (layer-2 WS-C3750-24P switches) but they don't wont to work. Applying the same config to any router or 4500/6500 chassis, and NTP authenticates straight away. NTP without authentication works fine on 3750s as well...
ntp authentication-key 1 md5 <key>
ntp authenticate
ntp trusted-key 1
ntp server 10.200.11.200 key 1
Is there additional config required for 3750s? This is across different IOS versions, so doesn't look like a bug..
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Sep 12, 2011
I'm testing QoS with a 3750-X
I want to mark traffic in the 192.168.126.0/24 subnet with DSCP EF.
I've entered this command :
mls qos
class-map match-any class_126
match access-group 2
policy-map mark_dscp_126
[Code]....
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Feb 20, 2013
I'm trying to enable dhcp server on it. done this how to [URL] It works, but unfortunately the client takes almost 2 min to get an ip.
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Jul 5, 2012
I just upgraded a stack of 4 3750s from 12.2(53)SE2 to 15.0(1)SE2. The stack took awhile to come back online (about 20 min). I wanted to make sure this isn't a compatibility issues with the Boot Loader which is (C3750X-HBOOT-M) Version 12.2(53r)SE2, RELEASE SOFTWARE (fc1).
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May 28, 2012
We have PC's that connect through the Siemens IP phones and back to the cisco 3750 which is connected to our core 6500 via L3. The phones use a voice VLAN and the PC's use another VLAN. The whole setup seems to work ok but I was just wondering if the QOS was configured correctly. Our current config on our 3750 switches are mls qos trust dscp on the port that connects to the phone and PC and mls qos trust dscp on the L3 links. The phones are configured for "QOS L2/L3"From the reading I've done so far it seems that any ports connected to a L2 device should be set to cos and not dscp?
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Jun 16, 2011
I could do configuration of a VPLS in 3750, I have doubt about whether the configuration is similar to that of 7600, but is so I could recommend some document to observe the configuration.
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Feb 1, 2011
I need to use a 3750 switch running 12.2 code to route between two networks in a test setup.Switch#sh verCisco IOS Software, C3750 Software (C3750-IPSERVICES-M), Version 12.2(25)SEE2, RELEASE SOFTWARE (fc1)Copyright (c) 1986-2006 by Cisco Systems, Inc. The idea for the test setup is 3750 emulates a client's live network which is two routers having a site-to-site tunnel connecting from their ISPs. This will allow me to test the tunnel configuration with the router configs that are in production but replacing one of the routers with an ASA.
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Oct 12, 2012
We are running CISCOWorks 4.0 (LMS).I can connect to and update the majority of my 3750's but I have about 20 that result in failure when attempting to update the image on those devices.The return error is "SWIM50001: Cannot connect to the device "IPAddress" using SSH and TELNET." When running "sho ssh" you see connection for the current ssh tectia login but nothing pointing to the ciscoworks device.When I run "sho ssh" from a different device I see both connections, 1 from my desktop ssh connection and the other showing username of ciscoworks.I ran the Discovery tool, again, but no joy.I was looking for a manual way to add that connection but again nothing. How to make the ssh connection between ciscoworks and the edge device?As I said I can ssh from my desktop and manage the box that way but ciscoworks simply won't allow it.
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Aug 15, 2011
I am into creating a new VLAN, what I have missed in the setup / configuration. I have multiple Cisco switches, the VLAN is configured on a 3750. My attempt was to place the VLAN on one port (as concept) and work from there - - so it is on 2-02 of my main Cisco stack. The new VLAN is 220 - Printer. My present IP scope is 192.168.200.x - running out of addresses - trying to add 192.168.220.x. on VLAN 220 to relieve some pressure - -- Most I can do is ping the VLAN IP - 192.168.220.1 and that resolves - - but if I attach a networked device with a 192.168.220.x address - - cannot get there..
Here is the switch info...
version 12.2
parser config cache interface
no service pad
service tcp-keepalives-in
service tcp-keepalives-out
service timestamps debug datetime msec localtime
service timestamps log datetime localtime
service password-encryption
[code]....
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May 17, 2011
I have an issue with connecting my OPTEMAN 100mb handoff to the 3750 ME ES ports. Because the ES ports will only accept gig connections, I am unable to use the ES ports.
Is there a work-around? It's too costly to have the OPTEMAN changed over to a GIG hand off and I really don't want to put in another piece of equipment to use the ES ports.
Is there a way to have the traffic flow into a 100mb port ont the 3750 and then over to the ES port?
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