I Like To Intentionally Create A Layer 2 Loop in My LabI have 2960 and 3750 switches and servers with multiple NIC's and also Some PC's and Hubs. Connections and Commands And Features Which Sould Be Disabled or Enabled)
View 4 Replieswe recently had on our network a simple layer 2 loop problem, with big effects.Here is the situation: we have a C3750 switch, with STP activate on all ports.We don't have total control on this switchs, and for some reasons, it is possible that people connect a 2d switch on it (Cisco or non-Cisco).What happened several times is a classic case: a person interconnect 2 ports of this 2d switch, creating a loop. As the loop is created on the 2d switch only, the 1st switch detect no loop, the the uplink port keeps up.Afer this loop created, a broadcast storm occurs through the link between 1st & 2d switch .. and the storm propgates all over the LAN.I try to find some solutions to avoid that. One thing I would like to do is to find a mecanism on the first switch, which can permit to block the uplink port on the 1st switch if it sees the same MAC address as source in the 2 directions.Note that storm control, even configured to a quite low value (ie: 2Mbps) is not efficient enough to protect equipment (we have had big CPU impact on LAN equipments).
View 3 Replies View RelatedIs it possible to to build a Layer 3 ether channel from two separate physical switches (layer3) that are trunked together?I know you can easily do this on a single switch and on stacked switches which I've done but in this case the customer have purchased two 3560X's which are not stackable yet want redundancy. The purpose of the etherchannel is to connect both switches to a private circuit provided by the hosted partner then route to the same setup in the DR location to different subnets.
View 4 Replies View RelatedI've created a scenario using a 3750 cisco as core switch ad other 6 switch model 2900 in access level.my problem is this, the router is not a cisco router, and this router is not able to make NAT on more than one subnet.Into the core switch I've created 4 VLAN and I must to give internet access to 3 of them, 192.168.0.0/24 (vlan1), 172.16.0.0/24 (vlan2), 172.17.0.0/24 (vlan3).I've connected the switch to router via gigabit ethernet 0/1 and I've assigned to this interface ip address 192.168.10.2, the router ip address is 192.168.10.1, Switch ip default-gateway is router ip address 192.168.10.1, ip default route is 0.0.0.0 0.0.0.0 192.168.10.1 I've enabled ip routing feature and I've set no switchport feature to interface gigabit ethernet 0/1.From core switch I can ping router ip address but I can't make it from all other user, and the users not able to have internet access.
Below the switch configuration (only necessary strings)
version 12.1
no service pad
service timestamps debug uptime
service timestamps log uptime
no service password-encryption
[code].....
As we know there are three layer in cisco Network Model:
-Core
-Distribution
-Access
So my question is in Core / Distribution layer should i use Etherchannel between switches or use Stacking if switches are stackble.For ex: suppose I have two cisco 3750 switches . so should i use etherchannel between them or use stacking in core layer?What are the advantages and disadv of both.
I've got a bunch of 3750-X switches all running IP Base and acting as a routed access layer. They run OSPF in a totally stubby area with the distribution layer (Nexus 7K) as the ABR. We also have a physically separate management network into which the fa0 management interface of the 3750-X is connected. The management network itself runs OSPF and has multiple subnets and external access.
On the 3750-X, I'd ideally like to be able to run some sort of separate OSPF process for the management network or at the very least have a static default route for management traffic pointing out the fa0 interface, but clearly not have it interfere with the main default route for data traffic coming from the N7K ABR. Normally I'd just create a management VRF, sling the fa0 interface into it and run a separate OSPF process in that VRF. The problem is you can't create VRFs in IP Base! Surely there must be a way to do this? Cisco don't really expect customers to upgrade to IP Services just to have a working OOB Management network, do they?!
My colleague and I have been having a discussion about using rapid spanning tree in the access layer. Most of our infrastructure has been migrated to a routed access layer with 3750s.
The idea was brought up to configure the switches with rapid PVST. On the surface, it seems like a better idea, faster convergence, in the event that spanning tree ends up being used for some reason. My colleague prefers sticking with standard PVST. His argument is that, in the event of a layer 2 loop, some consumer-level switches filter out BPDUs and if the control plane is overwhelmed, the shorter timers of rapid PVST just puts that much more of a burden on the CPU trying to regain control, whereas with standard PVST it will have around 20 seconds before it starts to engage. (It may still be overwhelmed, but the longer timer delays the additional burden.) He says he's seen this problem with rapid PVST and that his opinion is backed up by our Cisco rep. (I haven't spoken to him yet.)
In our model, it should be very rare -- pretty much never -- that we would layer 2 span another switch off of our access stack.
One suggestion I saw is to use BPDU Guard, which is a good suggestion as well.
But we have had experiences with overloading the control plane on a 3750. I believe that concern is valid. If the CPU can't service spanning tree. But I'm interested in hearing about other experiences people have had in terms of rapid spanning tree in the access layer, end users plugging in unauthorized devices and creating loops, and the effects when using rapid spanning tree vs standard spanning tree.
I configure 3750 stack switch as core and 2960 stack switches as access layer switches.I connected my laptop to one of my core stack in VLAN 10 and I am pinging to one of my server in VLAN 1. What will be the minimum latency at the time of inter VALN routing
View 2 Replies View RelatedCurrently have two routers inside our network.
One is the default GW 10.1.1.13
One is Jump Router for ATT 10.1.1.12
Both connected to HP Procurve L2 switch
The ATT Router is 10.1.1.2Want to replace GW and Jump with one 3750 L3 switch.icomplish this with only one port g0/1 connected to HP Procurve?Can I make the switchport 10.1.1.13 and then create a ip vlan999 10.1.1.12?route all to 10.1.1.2Or do I just connect two ports, and hardcode them with an ip?
I am looking for a way to create different routing policies for vlans on a 3750 table.
My set up is
Clients----------- 3750 -------------- ASA ---------------Servers
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Internet Routers
What i am trying to do is on the 3750 to route private networks to my ASA on different subintefaces and all internet to my internet routers . Each VLAN has a different GW for the internet. On some case i have the ASA as a default gateway. ASA default default route is 3750 where i need the internet traffic to be spllited on the proper Boarder router.
This is regarding VLAN creation on C3750E switch.I want to create new Vlan 94 on this switch and also I want to allowed same interfaces like Vlan 95 & Vlan 96. [code]
View 7 Replies View RelatedI want to setup VLAN with the switches SG300 and SLM2024. What is the suggestion to connect these 2 switches. We have the Juniper net screen.
View 1 Replies View RelatedI have a question if I Stack a Catalyst 3750 L3 with a Catalyst just L2, will we able to use all L3 capabilities?
Switches are
WS-C3750G-24TS-E1U
WS-C3750V2-24PS-S
I'm setting up a Cisco 3750 layer 3 switch with several vlans. I thought enabling routing would route between the vlans, but no such luck.What I want is to share the internet access of vlan 100 with the other vlans/ip-nets.How can I do that?
View 2 Replies View RelatedHow to create loopback cable for gig copper port (cisco 6513).I
View 3 Replies View RelatedI am trying to reproduce a Spanning-Tree loop in my lab that occurred on Ops, and for the life of me I cannot break it. The loop is very simple:
Cisco 2960------------FW that doesn't forward STP traffic-----------Cisco 2960
This created an STP loop. In my lab, I am substituting the FW for another Cisco 2960 with STP disabled and BPDUFilter on ingress/egress ports to stop the switch from sending BPDU's to the downstream switch to keep it in the dark, as the FW did on Ops.
We have a couple of cisco SGE switches connected to a single DELL, between the cisco switches we have a trunk interface. I'm not sure which setting should be configured on the switches to get it working because a loop is occuring.
View 1 Replies View RelatedI have a Catalyst 3560-X PoE that suddenly stopped working. I plugged in via console and below is the output I received. It scrolls constantly and I am unable to enter ROMMON mode or stop it from scrolling. I've read of a possible problem with the IOS version but I'm unable to verify due to not being able to stop the scrolling.
Switch uptime is 4 minutes, 4 seconds
cisco WS-C3560X-24P (PowerPC405) processor (revision A0) with 262144K bytes of memory.
Processor board ID FDO1522R2AY
[Code].....
We recently wanted to swap our existing WS-SUP720-base with a WS-SUP720-3B in a 6513 chassis.Had the existing configuration config saved in a txt file and replaced the supervisor. Booting went fine and we pasted in the original config. There was one failure message about unnsupported command but didnt take further notice."boot system flash sup-bootflash:" was probaly the line that the 720-3B didnt support.After wr mem and reload it went in continious loop and rebooting due to inncorrect boot device. Had to put back the old supervisor and have now the 720-3B in a 6504 chassis. Tried some commands in rommon, but are not getting any further.
View 8 Replies View RelatedI am having an issue with this device after setting the ip address and rebooting. I have tried renaming the config.text file without success. I have also tried the steps mentioned here: [URL]
View 1 Replies View RelatedI have a strange issue where spanning-tree is blocking vlans through a mesh network.Here is my set up.
2-Cisco 3560's that have two trunk ports set with do1q and a native vlan of 2. I'm allowing a client vlan (2) and a voice vlan (103) to come over the trunk. They have a native vlan of 2 so the mesh APs can get an address through DHCP. Spanning-tree loop guard is also enabled.
When connected to the mesh network, the voice vlan is being blocked by spanning-tree. I get the following erros:
000129: *Feb 28 19:24:58.289 EST: %SPANTREE-2-LOOPGUARD_BLOCK: Loop guard blocking port FastEthernet0/1 on VLAN0103.000130: *Feb 28 19:24:58.448 EST: %SPANTREE-2-LOOPGUARD_UNBLOCK: Loop guard unblocking port FastEthernet0/1 on VLAN0103.
Eventually the loop is cleared and the port is set back to a forwarding state from a blocking state. I don't want to disabled spanning-tree loopguard since I don't want to create a loop. The mesh network is supposed to act as a P2P connection between two switches. As a test I disconnected the APs from their trunk ports. I then used a cross over cable to connect the switches and no spanning tree loops occured. The mesh doesn't have STP enabled on it and should just be acting as an over-the-air connection from one switch to another.
I have an Extremely Old switch that I need to connect to my network. Because it is so old I don't want it to become the Root Switch.
what is the command to change the priority. (Honestly I don't remember if it has to be a lower number 1 or a higher number ). Always get that mixed up. I've read about root guard, but I would like to prevent it manually. (It is a small network after all)It is a Cisco 2950.
Do Cisco Catalyst (IOS) and specially Cisco SG300/500 support a similar feature to HP's Loop Protection or DLINK's Loopback Detection? This is an interesting feature to avoid loops caused by unmanaged switches.
View 6 Replies View RelatedI have a bunch of 3750x switches that each have a 10 gig routed link back to a central 4507 (loopback = 172.30.255.255).We carved up a /24 (of course, the /24 doesn't really exist except in our address tracking spreadsheet) into a bunch of /30's for routed WAN links and /32's for loopback addresses.We started on the low end for /30 subnets (ie 172.30.255.0/30, 172.30.255.4/30, etc.).We started at the high end for the /32 loopbacks (ie 172.30.255.255/32, 172.30.255.254/32, etc.)
Well, when I try pinging 172.30.255.255 from the access layer 3750x switches, the 3750x seems to be treating it as a broadcast ping where it lists each member that responds instead of the regular !!!!! response (this makes think something is odd with the 3750x). Of course, only one member responds (the core). But even the core seems to respond with the other end of the /30 instead of the actual /32 loopback (which makes me think something is odd in the core). I could have sworn that I've setup similar topologies without problems (ie, using 10.0.0.0/32, 10.255.255.255/32, etc as loopbacks) and as long as the mask is a /32, it should work.Also, I can ping/ssh to that loopback if my laptop is on a directly connected subnet. But I can't do it from any of the 3750x switches (which are also directly connected).I've double checked for overlapping subnets, but nope. I don't see any. Routing looks fine. The actual /32 is being propagated everywhere properly.
I have a 3925 Router with a 48 port switch module (part number SM-D-ES3G-48-P). I have no problem accessing the 3925 Router, but when I go into the 48 port, I get an error that reads
Error Hardware not supported by firmware. Try loading a newer software instead. System Resetting...
I know that the wrong IOS is installed on the switch, but the problem is that this is an endless loop. The switch resets then comes back to the same error. How to get the switch out of this loop so that I can load the correct IOS.
The following error was seen on the switch and the Diagnostic Test Loop back failed following a new WS-6748-SFP module installation.Fabric in slot 5 detected excessive flow-control on channel 3 (Module 4, fabric connection 1)
Tried Hard reset of the module and still the error persist.
I have a couple of 3560 switches running c3560-advipservicesk9-mz.122-44 and they are randomly experiencing the following:
- The switch locks up with no preceding error message in the log (I am forwarding syslog to Splunk).
- Upon reboot, the switch goes through the normal startup sequence with no error messages, then for some reason reloads the flash and starts all over again. (refer to doc)
This could happen after days or weeks. Sometimes they will go through two of these reloads on boot and be fine for awhile, and other times they will be stuck in the loop infinitely. I am using this same image with all of our 3560s, but am only having this issue with two of them.
i have recently tried to change the catos on a Catalyst 2948G-L3 and since then i have the following message in a loop :I know that the solution would be to download a new valid image from tftp via the rommon prompt but what i dont undertand is why i cant access the rommon prompt. It justs boots with the message above in a loop
View 0 Replies View RelatedWe have a Cisco 3750G Core switch which has physical connections, each configured as trunks to two HP Access switches. The client who uses these access switches would like to put a link between the two, but this would create a loop.
------- Core Switch -------
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[Code]....
I'm trying to configure an LACP channel trunk between a CatOS C6000 and a Dell PowerConnect.
I use mode active in both sides and it works great.
But, when I connect a Catalyst 3750X to the Dell PowerConnect the channel between C6000 and PWC shutdown:
2013 May 16 09:08:20 CEST +02:00 %SPANTREE-2-CHNMISCFG: STP loop - channel 5/19-20 is disabled in vlan/instance 20
2013 May 16 09:08:20 CEST +02:00 %SPANTREE-2-CHNMISCFG2: BPDU source mac addresses: 00-04-6d-43-a4-e2, 70-ca-9b-27-46-99
Here is my Lab Setup: 2691 is BGP nei to R4 router and they are not directly connected. 2691 and R4 are in same AS 6500. 2691 Config---router ospf 1 network 3.3.3.3 0.0.0.0 area 0 . Its advertising its loop back IP to OSPF domain.
router bgp 6500
no synchronization
bgp log-neighbor-changes
neighbor 6.6.6.6 remote-as 6500
neighbor 6.6.6.6 update-source Loopback3
[code]...
R4 Router
router ospf 11
log-adjacency-changes
network 6.6.6.6 0.0.0.0 area 0
[ code].....
We can see that 2691 and R4 are BGP neis and 2691 has 200.1.x.x routes in its route table. My question is why from 2691 router i am unable to ping any route learned by BGP from R4?
2691Router# ping 50.1.1.0 Type escape sequence to abort.Sending 5, 100-byte ICMP Echos to 50.1.1.0, timeout is 2 seconds:.....Success rate is 0 percent (0/5)2691Router#ping 200.1.2.0 [ code]...
we are bringing up new ckt and nexus 7000's interface isn't coming up once telco gave a loop. and wee following msg when I do "sh int eth1/1".
(UDLD Tx Rx loop, port: error)
what does "(UDLD Tx Rx loop, port: error)" it mean?before loop. interface was showing as "Link not Connected".
I am trying to configure a loop back interface like so: [URL], on the following device:
C3550 Software (C3550-IPSERVICESK9-M), Version 12.2(50)SE, RELEASE SOFTWARE (fc1on port gig0/1 which is using a 1000Base-SX adapter. This is for troubleshooting purposes and it does not appear to be a feasible option. Is there another way to accomplish in the IOS?